Revisiting Hiroshima in Iran

Revisiting Hiroshima
in Iran
What Americans Really Think about
Using Nuclear Weapons and Killing
Noncombatants

Scott D. Sagan and
Benjamin A.
Valentino

In August 1945, 85 per-
cent of the U.S. public told pollsters that they approved of President Harry
Truman’s decision to drop two atomic bombs on Hiroshima and Nagasaki.1
In the more than seven decades since that time, however, U.S. public approval
of the decision to use nuclear weapons against Japan has declined sig-
niªcantly. Seventy years after the end of the World War II, a majority of Ameri-
cans no longer approved of Truman’s decision: a 2015 poll found that only
46 percent of Americans still viewed the atomic bombing of Japan as “the right
thing to do.”2

What accounts for this apparent decline in U.S. public support for using nu-
clear weapons and what is its signiªcance? The answers to these questions are
of more than just historical interest, for they can provide insights into whether
the U.S. public would be a constraint against or a goad to encouraging a presi-
dent to use nuclear weapons in international crises or conºicts in the future.
The answers to these questions also help scholars and policymakers under-
stand how Americans think about killing foreign civilians in war and how well
they have internalized the principles of just war doctrine, such as noncomba-
tant immunity, proportionality, and risk acceptance.

An initial review of U.S. public opinion on the decision to drop the bomb
provides both a vivid reminder of the depth of hostility that Americans felt to-

Scott D. Sagan is the Caroline S.G. Munro Professor of Political Science, the Mimi and Peter Haas Univer-
sity Fellow in Undergraduate Education, and Senior Fellow at the Center for International Security and Co-
operation, the Freeman Spogli Institute for International Studies, at Stanford University. Benjamin A.
Valentino is Associate Professor of Government at Dartmouth College.

The authors thank Barton Bernstein, Joanne Gowa, David Holloway, Maral Mirshahi, Andrew
Reddie, Adam Roberts, Sarah Sadlier, Todd Sechser, Rachel Stein, Nina Tannenwald, Allen Weiner,
and William Wohlforth for helpful comments on earlier drafts of this article. They also thank par-
ticipants in seminars in which they presented this work at Stanford University, Yale University, the
University of Virginia, the George Washington University, the University of California, Berkeley,
the Massachusetts Institute of Technology, and the London School of Economics. Funding for this
project was received from the MacArthur Foundation, Stanford’s Freeman Spogli Institute, Stan-
ford’s McCoy Family Center for Ethics in Society, and the Naval Postgraduate School’s Project on
Advanced Systems and Concepts for Countering Weapons of Mass Destruction.

1. David W. Moore, “Majority Supports Use of Atomic Bomb on Japan in WWII,” Gallup, Au-
gust 5, 2005, http://www.gallup.com/poll/17677/majority-supports-use-atomic-bomb-japan-wwii
.aspx.
2. Peter Moore, “A-Bomb Legacy: Most Americans Negative about the Invention of Nuclear
Weapons” (Redwood City, Calif.: YouGov, July 22, 2015), https://today.yougov.com/news/2015/
07/22/a-bomb-legacy/.

International Security, Vol. 42, No. 1 (Summer 2017), pp. 41–79, doi:10.1162/ISEC_a_00284
© 2017 by the President and Fellows of Harvard College and the Massachusetts Institute of Technology.

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International Security 42:1 42

ward Japan in 1945 and a strong sense of declining support for the use of nu-
clear weapons since then. A University of Chicago National Opinion Research
Center poll administered in September 1945 found that 44 percent of the public
said the United States should have dropped the bombs “one city at [a] time”;
26 percent said that it should have dropped the bomb “where [there were]
no people”; 23 percent said the United States should have “wiped out [all
Japanese] cities”; and only 4 percent said they would have “refused to use” the
bomb.3 A Roper poll published later that year in Fortune magazine similarly
found that just 4.5 percent of the U.S. public believed that the United States
should not have used atomic bombs at all; 13.8 percent believed that it should
have ªrst dropped a bomb on an unpopulated area; 53.5 percent maintained
that it should have used the two bombs on two cities, as it did; and 22.7 per-
cent believed that it should have dropped more bombs before Japan had the
chance to surrender.4

Although the percentage of Americans approving of Truman’s decision
has ºuctuated over time—in part because of the varied wording of survey
questions, and whether alternatives to “approve” or “not approve” response
categories were included in the polls—U.S. public support for dropping the
bombs on Hiroshima and Nagasaki has been on a downward trajectory. For
example, Harris polls in 1971 and 1982 found that 64 percent and 63 percent of
Americans, respectively, deemed it “necessary and proper” to drop the atomic
bombs on Japan. In contrast, a 1998 Roper poll found that only 47 percent
thought that dropping the bombs was “a right thing,” 26 percent said that it
was “a wrong thing,” and 22 percent were somewhere between the two ex-
tremes.5 Polls conducted by the Associated Press in March and July 2005
showed that, respectively, 47 percent and 48 percent of the public “approved”
of the dropping of atomic bombs on Hiroshima and Nagasaki.6

3. “Survey by National Opinion Research Center, September, 1945,” conducted by the National
Opinion Research Center, University of Chicago (1945; Ithaca, N.Y.: iPoll, Roper Center for Public
Opinion Research, Cornell University, n.d.), https://ropercenter.cornell.edu/CFIDE/cf/action/
ipoll/questionDetail.cfm?keyword(cid:2)&keywordoptions(cid:2)1&exclude(cid:2)&excludeOptions(cid:2)1&topic
(cid:2)Any&organization(cid:2)National%20Opinion%20Research%20Center&label(cid:2)&fromdate(cid:2)01/01/
1945&toDate(cid:2)12/31/1945&stitle(cid:2)&sponsor(cid:2)&studydate(cid:2)September,%201945&sample(cid:2)1262
&qstn_list(cid:2)&qstnid(cid:2)13397&qa_list(cid:2)&qstn_id4(cid:2)13397&study_list(cid:2)&lastSearchId(cid:2)31767087608
8&archno(cid:2)USNORC1945-0237&keywordDisplay(cid:2).
4. “The Fortune Survey,” Fortune, November 30, 1945, reprinted in “The Quarter’s Poll,” Public
Opinion Quarterly, Vol. 9, No. 4 (Winter, 1945/46), p. 530, doi:10.1086/265765.
5. Louis Harris, “The American View of Japan and the Japanese: A Sharp Decline in Racism but
Memories of WWII Still Linger,” Harris Survey, April 19, 1982, http://media.theharrispoll.com/
documents/Harris-Interactive-Poll-Research-THE-AMERICAN-VIEW-OF-JAPAN-AND-THE-
JAPANESE-A-SHAR-1982-04.pdf; and Carl Brown, “Public Opinion about Using Nuclear
Weapons” (Ithaca, N.Y.: Roper Center for Public Opinion Research, Cornell University, n.d.), http://
ropercenter.cornell.edu/public-opinion-using-nuclear-weapons/.
6. Ipsos Public Affairs, “The Associated Press Poll,” Associated Press, March 24, 2005, http://

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Revisiting Hiroshima in Iran 43

Table 1. 2015 Replication of the Roper/Fortune 1945 Poll

Polling in the United States on the Use of Atomic Bombs on Japan

Polling Question: “Which of these comes
closest to describing how you feel about our
use of the atomic bomb?”

Elmo Roper
“Atomic Bomb” Poll
(November 30, 1945)

Roper 1945 Poll
Replication
(July 30, 2015)

“We should not have used any atomic bombs
at all.”

“We should have dropped one ªrst on some
unpopulated region, to show the Japanese its
[atomic bombs’] power, and dropped the
second one on a city only if they hadn’t
surrendered after the ªrst one.”

“We should have used the two bombs on
cities, just as we did.”

“We should have quickly used many more of
them before Japan had a chance to
surrender.”

“Don’t know.”

4.5%

13.8%

53.5%

22.7%

5.5%

14.4%

31.6%

28.5%

2.9%

22.7%

SOURCES: “The Fortune Survey,” Fortune, November 30, 1945, reprinted in “The Quarter’s
Poll,” Public Opinion Quarterly, Vol. 9, No. 4 (Winter, 1945/46), p. 530; and “Japan
1945 Poll Replication” (Redwood City, Calif.: YouGov, July 30, 2015).

The downward trend has continued in recent years. Indeed, when we repli-
cated the 1945 Roper poll in a July 2015 poll (table 1), both of which included a
“demonstration strike” option, we found that in 2015 less than 30 percent of
the U.S. public supported dropping the two bombs (down from 53.5 percent in
1945), whereas 31.6 percent said they preferred the demonstration strike (up
from 13.8 percent in 1945). The percentage of Americans who felt that the
United States should not have used any atomic bombs more than tripled from
1945 to 2015, and the percentage of Americans who felt that it should have
used more bombs before Japan had a chance to surrender dropped from
22.7 percent in 1945 to less than 3 percent seventy years later.7

Unlike these polls, which examined support for the use of the atomic bombs
against Japan in 1945, other polls have focused on U.S. attitudes about contem-
porary conditions in which the United States might use nuclear weapons. The
evidence here also suggests a general decline in support for using nuclear
weapons. In 1949, for example, only 20 percent of the U.S. public agreed that

surveys.ap.org/data/Ipsos/national/2005/2005-03-23%20AP%20Topline%20results.pdf; and Ipsos
Public Affairs, “Associated Press World War II/Japan Study,” Associated Press, July 12, 2005,
http://surveys.ap.org/data/Ipsos/national/2005/2005-07-11%20AP%20_World%20War%20II_
%20topline%20results.pdf.
7. We do not know, however, what percentage of respondents who preferred a demonstration
strike would have supported the attacks on Hiroshima and Nagasaki had the demonstration strike
failed to cause the Japanese government to surrender.

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International Security 42:1 44

“the United States should pledge that we will never use the atomic bomb in
warfare until some other nation has used it on us ªrst.”8 In contrast, a 2010
Chicago Council on Global Affairs survey found that 57 percent of the public
agreed that “the U.S. should only use nuclear weapons in response to a nuclear
attack by another nation” and that 20 percent agreed that “the U.S. should
never use nuclear weapons under any circumstances.”9

Many scholars and policymakers—following the lead of Nina Tannenwald
in her important book The Nuclear Taboo—have pointed to the decline in U.S.
public support for using nuclear weapons as evidence of the gradual emer-
gence of an ethical norm, a taboo, against the ªrst use of nuclear weapons.10
Other scholars—most prominently, Steven Pinker, Neta Crawford, and Ward
Thomas—have contended that the decline in support for using nuclear weap-
ons is part of a much larger “humanitarian revolution” among the pub-
lic, which has led to a broad acceptance of the just war doctrine principle of
noncombatant immunity.11 A third school of thought—featured most promi-
nently in the work of Alexander Downes, Daryl Press, Scott Sagan, and
Benjamin Valentino—has argued that the U.S. public has internalized neither
the nuclear taboo nor a noncombatant immunity norm. These scholars contend
that Americans appear to be willing both to support the use of whatever
weaponry is deemed most effective militarily and to kill foreign civilians on a
massive scale whenever such attacks are considered useful to defend critical
U.S. national security interests and protect the lives of signiªcant numbers
of U.S. military personnel.12

In this article, we address these debates about U.S. public opinion concern-
ing nuclear use and noncombatant immunity. We argue that the previous polls

8. George H. Gallup, ed., The Gallup Poll: Public Opinion, 1935–1971, Vol. 1: 1935–1948 (New York:
Random House, 1972), p. 839.
9. Chicago Council on Global Affairs, “Global Views 2010” (Chicago: Chicago Council on Global
Affairs, September 22, 2010), pp. 99–100, https://www.thechicagocouncil.org/sites/default/ªles/
Global%20Views%202010_USTopline.pdf.
10. Nina Tannenwald, The Nuclear Taboo: The United States and the Non-Use of Nuclear Weapons since
1945 (New York: Cambridge University Press, 2007).
11. See Steven Pinker, The Better Angels of Our Nature: Why Violence Has Declined (New York: Vi-
king, 2011); Neta C. Crawford, Accountability for Killing: Moral Accountability for Collateral Damage in
America’s Post-9/11 Wars (New York: Oxford University Press, 2013); Neta C. Crawford, “Targeting
Civilians and U.S. Strategic Bombing Norms: Plus ça change, plus c’est la même chose?” in Matthew
Evangelista and Henry Shue, eds., The American Way of Bombing: Changing Ethical and Legal Norms,
from Flying Fortresses to Drones (Ithaca, N.Y.: Cornell University Press, 2014), pp. 64–86; and Ward
Thomas, The Ethics of Destruction: Norms and Force in International Relations (Ithaca, N.Y.: Cornell
University Press, 2001).
12. See Alexander B. Downes, Targeting Civilians in War (Ithaca, N.Y.: Cornell University Press,
2008); and Daryl G. Press, Scott D. Sagan, and Benjamin A. Valentino, “Atomic Aversion: Experi-
mental Evidence on Taboos, Traditions, and the Non-Use of Nuclear Weapons,” American Political
Science Review, Vol. 107, No. 1 (February 2013), pp. 188–206, doi:10.1017/S0003055412000597.

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Revisiting Hiroshima in Iran 45

showing a decline in support for the atomic bombings in 1945 and contempo-
rary uses of nuclear weapons are a misleading guide to understanding the real
views of the American public about the use of nuclear weapons and the killing
of noncombatants. Such polls failed to place respondents into a mind-set in
which they are forced to make a trade-off between risking U.S. soldiers’ lives
(if the United States does not use nuclear weapons) and killing foreign non-
combatants (if the United States does use nuclear weapons). Yet, precisely this
type of trade-off was at the heart of Truman’s decision in 1945; and scenarios
that entail this kind of trade-off are arguably among the most realistic and seri-
ous conditions in which a president and the public would be forced to contem-
plate the use of nuclear weapons in the future.

The ªrst section of the article reviews the three main schools of thought
about public attitudes toward the use of nuclear weapons and the killing of
foreign noncombatants. The second section presents the ªndings from a sur-
vey experiment conducted in July 2015 in which a representative sample of the
U.S. public was asked about a contemporary, hypothetical scenario designed
to replicate the 1945 decision—the use of a nuclear weapon against a city in
Iran in an attempt to end a war that the Iranian government had started in re-
sponse to the imposition of U.S. economic sanctions. This type of thought ex-
periment obviously cannot re-create the depth of urgency and emotion that
many Americans felt in 1945. As such, it constitutes a conservative test of the
public’s willingness to use nuclear weapons and target large numbers of non-
combatants in a war.

The ªndings demonstrate that, contrary to the nuclear taboo thesis, a clear
majority of Americans would approve of using nuclear weapons ªrst against
the civilian population of a nonnuclear-armed adversary, killing 2 million
Iranian civilians, if they believed that such use would save the lives of 20,000
U.S. soldiers. In addition, contrary to the noncombatant immunity norm the-
sis, an even larger percentage of Americans would approve of a conventional
bombing attack designed to kill 100,000 Iranian civilians in the effort to intimi-
date Iran into surrendering (see table 2).

The third section of the article analyzes the reasons why so many Americans
in our scenarios approved of using nuclear weapons. We present demographic
data on the key characteristics of the supporters of nuclear use and demon-
strate how our survey respondents explained their preferences about whether
or not to use nuclear weapons. Here we present some novel ªndings showing
that women support nuclear weapons use and violations of noncombatant im-
munity no less (and in some cases more) than male respondents. We also pro-
vide insights into how a belief in retribution and an ability to assign culpability
retrospectively to foreign civilians allows individuals to rationalize the killing

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International Security 42:1 46

Table 2. Iran Bombing Conditions

Expected U.S. Fatalities
in Ground Assault

Expected Iranian Fatalities in Air Attack

20,000 U.S. troops dead 100,000
Iranian civilians dead in nuclear attack
20,000 U.S. troops dead 2,000,000 Iranian civilians dead in nuclear attack
20,000 U.S. troops dead 100,000

Iranian civilians dead in conventional bombing attack

of foreign noncombatants. In the fourth section, we present the results of a re-
lated survey experiment constructed to determine whether Americans would
support a diplomatic compromise in a war with Iran to avoid either the killing
of U.S. soldiers or the killing of foreign noncombatants. In the concluding sec-
tion, we outline a future research agenda to further understand these phenom-
ena and present the implications of our ªndings for debates about just war
doctrine and the risk of the use of nuclear weapons in future conºicts.

The Nuclear Taboo, Noncombatants, and Military Effectiveness

There are three main schools of thought about U.S. public opinion and the use
of nuclear weapons against civilian targets. The ªrst theory, advanced most
clearly in the work of Nina Tannenwald, is that over time both U.S. leaders
and the public have internalized a belief in a “nuclear taboo.” According to
Tannenwald, “The taboo is not the behavior (of non-use) itself but rather the
normative belief about the behavior . . . a shared expectation about behavior, a
standard of right and wrong.”13 Tannenwald insists that “leaders and publics
have come to view this phenomenon not simply as a rule of prudence but as a
taboo, with an explicit normative aspect, a sense of obligation attached to it.”14
For Tannenwald, and many others, decreasing public support over time for
dropping the atomic bombs in 1945 is clear evidence that a nuclear taboo ex-
ists. Tannenwald, for example, has argued that “the public’s changing inter-
pretation of the correctness of Hiroshima and Nagasaki over the years is
perhaps explicable in the terms of a general delegitimation of nuclear weap-

13. Tannenwald, The Nuclear Taboo, p. 10. For the alternative view that the non-use of nuclear
weapons is caused by U.S. leaders’ concerns about setting a precedent that might lead to future
nuclear weapons use by others, see T.V. Paul, The Tradition of Non-Use of Nuclear Weapons (Stanford,
Calif.: Stanford University Press, 2009); and Scott D. Sagan, “Realist Perspectives on Ethical Norms
and Weapons of Mass Destruction,” in Sohail H. Hashmi and Steven P. Lee, eds., Ethics and
Weapons of Mass Destruction: Religious and Secular Perspectives (Cambridge: Cambridge University
Press, 2004), pp. 73–95.
14. Tannenwald, The Nuclear Taboo, p. 14.

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Revisiting Hiroshima in Iran 47

ons.”15 Peggy Noonan, special assistant and head speech writer for President
Ronald Reagan, credits John Hersey’s book, Hiroshima, for a universal moral
repulsion against the bomb: “Hiroshima did a huge and historic thing. It not
only told the world what happened when a nuclear weapon was used, it
single-handedly put a powerful moral taboo on its future use. After Hiroshima,
which sold millions of copies, no one wanted it to happen again.”16 Jeffrey
Lewis similarly traces the origin of the nuclear taboo to Hersey’s book and
maintains that “[o]ver time, we’ve come to see nuclear weapons as Hersey
saw them, as the ultimate expression of material and spiritual evil of total
war. . . . The implication of this norm, of course, is that we can’t actually use
nuclear weapons.”17 Thomas Schelling, in his 2005 Nobel Prize speech—“An
Astonishing Sixty Years: The Legacy of Hiroshima”—referred to and cele-
brated the “nearly universal revulsion against nuclear weapons.”18 In 2008,
United Nations Secretary-General Ban Ki-moon also praised the existence of
a nuclear taboo while lamenting that it had not led to nuclear disarma-
ment: “Despite a longstanding taboo against using nuclear weapons, dis-
armament remains only an aspiration.”19

The nuclear taboo literature has shown that some U.S. leaders, during spe-
ciªc crises or wars, have felt that they were constrained by public opposition
to the United States initiating the use of nuclear weapons. Tannenwald, for ex-
ample, notes that Secretary of State John Foster Dulles commented in a 1953
National Security Council discussion about nuclear use in Korea that the pub-
lic believed there to be a “moral problem” with these weapons and suggested
that the Dwight Eisenhower administration actively “break down this false
distinction” so that nuclear weapons would be viewed “as simply another
weapon in our arsenal.”20 William Burr and Jeffrey Kimball, and Scott
Sagan and Jeremi Suri, have similarly demonstrated that President Richard

15. Ibid., p. 374. See also Beatrice Heuser, The Bomb: Nuclear Weapons in Their Historic, Strategic, and
Ethical Context (London: Longmans, 2000).
16. Peggy Noonan, “Misplaying America’s Hand with Iran,” Wall Street Journal, April 2, 2015,
http://www.wsj.com/articles/peggy-noonan-misplaying-americas-hand-with-iran-1428019612.
17. Jeffrey Lewis, “Magical Thinking and the Real Power of Hiroshima,” Foreign Policy, August 6,
2015, http://foreignpolicy.com/2015/08/06/magical-thinking-and-the-real-power-of-hiroshima-
nuclear-weapons-japan/.
18. Thomas C. Schelling, “An Astonishing Sixty Years: The Legacy of Hiroshima,” Nobel Prize lec-
ture, December 8, 2005, http://www.nobelprize.org/nobel_prizes/economic-sciences/laureates/
2005/schelling-lecture.pdf.
19. Ban Ki-moon, “Five Steps to a Nuclear-Free World,” Guardian, November 23, 2008, http://
www.theguardian.com/commentisfree/2008/nov/23/nuclear-disarmament-united-nations.
20. NSC meeting, February 11, 1953, Foreign Relations of the United States (FRUS), 1952–54, Vol. 15,
Part 1: Korea (Washington, D.C.: Government Printing Ofªce [GPO], 1984), p. 770, quoted in Nina
Tannenwald, “The Nuclear Taboo: The United States and the Normative Basis of Nuclear Non-

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International Security 42:1 48

Nixon felt constrained in his ability even to threaten to use nuclear weapons
against North Vietnam, as part of his “madman theory” of nuclear coercion,
and therefore had to resort to a “secret” (and less effective) nuclear alert in
October 1969.21

Still, a number of weaknesses of the existing tests of the nuclear taboo thesis
are worth noting. First, although there is historical evidence that some U.S.
presidents felt constrained by U.S. public opinion in particular crises or con-
ºicts, scholars have not systematically studied contemporary public opinion
polls on nuclear weapons use in those periods. Thus, we do not know if these
leaders’ perceptions of public opposition were accurate. Second, polls showing
declining support for the bombing of Hiroshima and Nagasaki do not tell us
whether the decrease in support reºects changes in the U.S. public’s attitudes
toward using nuclear weapons or changes in attitudes toward Japan and in-
creasing temporal distance from the pressures of the war. It was much easier
for Americans to support using nuclear weapons against an adversary in a
brutal war in 1945 than it is to imagine using such weapons today against
Japan, one of the United States’ closest allies. In addition, these polls rarely
speciªed the known or expected numbers of civilians killed in atomic bombing
attacks or whether they were targeted intentionally. Consequently, it was up to
the respondents and their knowledge of the past to judge whether the use of
nuclear weapons conformed with the principle of noncombatant immunity or
proportionality (whether the costs of civilian deaths were proportionate to the
beneªts gained). And most important, existing polls have not forced survey re-
spondents to contemplate the trade-off between the use of nuclear weapons,
including the resulting loss of civilian lives in the adversary’s nation, and the
use of U.S. ground troops in an invasion and the resulting loss of American
soldiers’ lives.

the noncombatant immunity norm

A second school of thought argues that an even broader norm has constrained
the conduct of war in recent years. Proponents of this view assert that a phe-
nomenon that Steven Pinker has called “the Humanitarian Revolution” has
led to a deeply embedded and widely held norm against killing noncomba-
tants, regardless of the choice of weapon. Pinker argues that the strengthen-
ing of “the better angels of our nature . . . can be credited for declines in

Use,” International Organization, Vol. 53, No. 3 (Summer 1999), pp. 448–449, https://doi.org/
10.1162/002081899550959.
21. William Burr and Jeffrey P. Kimball, Nixon’s Nuclear Specter: The Secret Alert of 1969, Madman
Diplomacy, and the Vietnam War (Lawrence: University of Kansas Press, 2015); and Scott D. Sagan

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Revisiting Hiroshima in Iran 49

violence.”22 He contrasts the common popularity of cruel criminal punish-
ments and the brutality of soldiers in war in the past to more civilized norms
today and suggests that both rational choice and emotional development have
been at play: “The expansion of empathy may help explain why people today
abjure cruel punishments and think more about the human costs of war. . . .
The decline of violence may owe something to an expansion of empathy, but it
also owes much to harder-boiled faculties like prudence, reason, fairness, self-
control, norms and taboos, and conceptions of human rights.”23 For Pinker,
“The nuclear taboo emerged only gradually. . . . It began to sink in that the
weapons’ destructive capacity was of a different order from anything in his-
tory, that they violated any conception of proportionality in the waging of
war.”24 Yet Pinker clearly considers the nuclear taboo part of a broader phe-
nomenon, a change in what kind of killing in conventional and nuclear war is
deemed morally and politically acceptable by most Americans. “By the 1990s,”
he writes, “the only politically acceptable American wars were surgical routs
achieved with remote-control technology. They could no longer be wars of at-
trition that ground up soldiers by the tens of thousands, nor aerial holocausts
visited on foreign civilians as in Dresden, Hiroshima, and North Vietnam.”25
Ward Thomas extends this argument, asserting that the noncombatant im-
munity “norm has in recent decades engendered sensitivity to noncombatant
casualties that not only constrains states from targeting civilian populations
per se but also creates pressures to minimize incidental casualties in gen-
eral.”26 Thomas argues that the dropping of the atomic bombs on Hiroshima
and Nagasaki had “an ironic effect” in that “the postwar invigoration of the
bombing norm [by which he means the noncombatant immunity norm] owes
much to visceral moral reactions to the nightmare of World War II.”27 Al-
though he acknowledges that the noncombatant immunity norm is “far from
absolute,” Thomas does assert that the experience of World War II bombing
created a sea change in popular attitudes: “While unrestricted city bombing re-
mained an awesomely destructive means of warfare, in the postwar world

and Jeremi Suri, “The Madman Nuclear Alert: Secrecy, Signaling, and Safety in October 1969,”
International Security, Vol. 27, No. 4 (Spring 2003), pp. 150–183, doi:10.1162/016228803321951126.
22. Pinker, The Better Angels of Our Nature, p. 573.
23. Ibid., p. 572. For analyses of the evolution of the deªnitions of combatant and noncombatant,
see Helen M. Kinsella, The Image before the Weapon: A Critical History of the Distinction between Com-
batant and Noncombatant (Ithaca, N.Y.: Cornell University Press, 2011); and Sahr Conway-Lanz, Col-
lateral Damage: Americans, Noncombatant Immunity, and Atrocity after World War II (New York:
Routledge, 2006).
24. Pinker, The Better Angels of Our Nature, pp. 270–271.
25. Ibid., p. 264.
26. Thomas, The Ethics of Destruction, p. 148.
27. Ibid., p. 170.

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International Security 42:1 50

it seemed to offend, more than it had previously, people’s ‘sense of what
is right.’”28

Similarly, Neta Crawford, in her work on the evolution of U.S. airpower op-
erations, argues that “changes in the normative beliefs (beliefs about what is
right and wrong) of elites and the general public about targeting civilians
caused the United States to alter its bombing practices.”29 Crawford also con-
nects this explanation to the experience of World War II strategic bombing: “To
the extent they adopted the principle of civilian immunity, it was part of a
global change in views about human rights—viz., that there is something
called human rights and they belong to civilians of all sides, even in war.
The carnage of the two World Wars, of course, encouraged the development
of human rights norms. . . . This greater respect for human rights also, in-
cidentally, underpins the increased emphasis on force protection; it is no
longer acceptable to use soldiers as mere tools whose lives may be ‘wasted’
in the thousands.”30

The secondary point that both Pinker and Crawford make—that an in-
creased commitment to human rights could lead to both an increased commit-
ment to noncombatant immunity and a decreased willingness to sacriªce the
lives of soldiers in war—underscores an inherent tension in the logic of their
arguments. By not addressing whether these two factors might cancel each
other out or whether one is much stronger than the other, they cannot predict
or measure what the overall effect of such evolutionary norms might be.31
Even if there is a greater acceptance of the principle of noncombatant immu-
nity among the American public, does this counteract the effects of a decreased
willingness to accept fatalities among U.S. military personnel in war?32

28. Ibid., pp. 148, 170.
29. Crawford, “Targeting Civilians and U.S. Strategic Bombing Norms,” pp. 65–66. Crawford’s ar-
gument is not monocausal, however. She also stresses the role of elite understandings about the
military efªcacy (or lack thereof) of killing enemy civilians, as well as leadership concerns that kill-
ing enemy civilians can turn one’s own population or allied public opinion against the war. See
ibid., pp. 66–68; and Crawford, Accountability for Killing.
30. Crawford, “Targeting Civilians and U.S. Strategic Bombing Norms,” p. 65. Michael Walzer
similarly argued that U.S. bombing in the 1991 Gulf War was far more limited and selective than in
previous military campaigns, because “Bush and his generals believed that these people would
not tolerate the slaughter of civilians and they were probably right.” Walzer, Arguing about War
(New Haven, Conn.: Yale University Press, 2002), p. 11. See also Janina Dill, Legitimate Targets? So-
cial Construction, International Law, and US Bombing (Cambridge: Cambridge University Press,
2015).
31. On how leaders respond when different norms and taboos conºict, see Thomas M. Dolan,
“Unthinkable and Tragic: The Psychology of Weapons Taboos in War,” International Organization,
Vol. 67, No. 1 (January 2013), pp. 37–63, doi:10.1017/S0020818312000379; and Paul Kowert and
Jeffrey Legro, “Norms, Identity, and Their Limits: A Theoretical Reprise,” in Peter J. Katzenstein,
ed., The Culture of National Security: Norms and Identity in World Politics (New York: Columbia Uni-
versity Press, 1996), pp. 451–497.
32. For studies that demonstrate that past and projected military fatalities inºuence public sup-
port for war, see Scott S. Gartner, “The Multiple Effects of Casualties on Public Support for War:

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Revisiting Hiroshima in Iran 51

winning the war and saving u.s. troops

A third school of thought maintains that the American people have internal-
ized neither a nuclear taboo nor an unconditional norm supporting the princi-
ple of noncombatant immunity. Instead, scholars in this school argue that
concerns about winning wars and the desire to minimize the loss of lives of
their nation’s soldiers dominate public opinion about military operations.
Alexander Downes, for example, examined all known cases of “civilian victim-
ization” in interstate war from 1816 to 2003, deªning civilian victimization as
“a military strategy in which civilians are either targeted intentionally or force
is used indiscriminately” and that produces at least 50,000 noncombatant
deaths.33 Drawing on quantitative data and historical case studies, he con-
cludes that “states—including democracies—tend to prize victory and pre-
serving the lives of their own people above humanity in warfare: desperation
overrides moral inhibitions against killing noncombatants.”34 Indeed, con-
trary to theories that emphasize that authoritarian regimes are more likely
to target and kill foreign noncombatants, Downes found that electoral pres-
sures on leaders in democracies make them “somewhat more likely than non-
democracies to target civilians.”35

Downes’s work has three limitations, however, that reduce the applicability
of its insights to the speciªc questions we explore here. First, Downes did not
directly assess public support or lack of support for mass killings, leaving
open the possibility that democratic leaders incorrectly assumed that public
support for violence against foreign civilians was high. Second, his research in-
cluded both cases in which the killing of civilians was intentional and cases in
which it occurred as a result of collateral damage, which limits the degree
to which his ªndings can be said to measure support or rejection of the princi-
ple of noncombatant immunity. Third, all of Downes’s main case studies focus
on events that occurred in the ªrst half of the twentieth century, before many
scholars believe that the nuclear taboo and norms of noncombatant immunity
were ªrmly established.

A second major contribution to this school of thought is Christopher Gelpi,
Peter Feaver, and Jason Reiºer’s 2009 study, Paying the Human Costs of War:

An Experimental Approach,” American Political Science Review, Vol. 102, No. 1 (February 2008), pp.
95–106, doi:10.1017/S0003055408080027; Eric V. Larson, Casualties and Consensus: The Historical Role
of Casualties in Domestic Support for U.S. Military Operations (Santa Monica, Calif.: RAND Corpora-
tion, 1996); John E. Mueller, “Trends in Popular Support for the Wars in Korea and Vietnam,”
American Political Science Review, Vol. 65, No. 2 (June 1971), pp. 358–375, doi:10.2307/1954454; and
Benjamin A. Valentino, Paul K. Huth, and Sarah E. Croco, “Bear Any Burden? How Democracies
Minimize the Costs of War,” Journal of Politics, Vol. 72, No. 2 (April 2010), pp. 528–544, doi:10.1017/
S0022381609990831.
33. Downes, Targeting Civilians in War, p. 44.
34. Ibid., pp. 3–4.
35. Ibid., p. 3.

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International Security 42:1 52

American Public Opinion and Casualties in Military Conºicts, which focuses pri-
marily on how changes in real or estimated U.S. military casualties over time
inºuence public support for ongoing or potential U.S. wars.36 Although their
book does not investigate potential nuclear-weapons-use scenarios, it does in-
clude a brief analysis of how expected civilian casualties in an enemy country
might inºuence U.S. public support for starting a war. They acknowledge that
there is often an “unavoidable trade-off between their civilian casualties and
our military casualties” and therefore ask “how does the public weigh that
trade-off and what, to use an infelicitous metaphor from economics, is the
exchange rate?”37

Gelpi, Feaver, and Reiºer conducted an original survey experiment measur-
ing U.S. public support for an attack on North Korea to destroy its nuclear pro-
gram. They found, unsurprisingly, that support for an attack was higher
(60 percent) when no casualty estimates were mentioned, but dropped (by six-
teen percentage points to 44 percent) when the survey informed participants
that the attack would result in 2,000 U.S. military fatalities. Surprisingly, how-
ever, when a separate sample of the public was given a scenario that estimated
that 2,000 North Korean civilians would be killed in the U.S. attack, an almost
identical drop in U.S. public support for the attack was recorded. This ªnding
could suggest that the U.S. public holds a cosmopolitan view about justice in
war: that all human life has equal moral worth and therefore the lives of North
Korea civilians should be valued as highly as the lives of U.S. soldiers.38 Alter-
natively, because the experiments drew on separate representative samples of
the U.S. public, the result could simply reveal that there is a signiªcant drop in
support for starting an attack whenever any casualties—U.S. military, enemy
civilians, or allied civilians—are mentioned.39 Moreover, the experiment did
not include a condition in which the same respondents were asked about a
direct trade-off between killing U.S. soldiers and killing North Korean civil-
ians, nor did it ask respondents to consider the intentional targeting of North
Korean civilians. All respondents, however, were asked: “In general, how
would you rate the importance of limiting American military deaths as com-
pared to limiting foreign civilian deaths? Is limiting U.S. military deaths much
more important, somewhat more important, about equally important, some-
what less important, or much less important than limiting foreign civilian

36. Christopher Gelpi, Peter D. Feaver, and Jason Reiºer, Paying the Human Costs of War: American
Public Opinion and Casualties in Military Conºicts (Princeton, N.J.: Princeton University Press, 2009),
p. 255 (emphasis in the original).
37. Ibid., p. 256.
38. See Cécile Fabre, Cosmopolitan War (Oxford: Oxford University Press, 2012).
39. Gelpi, Feaver, and Reiºer, Paying the Human Costs of War, p. 256.

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Revisiting Hiroshima in Iran 53

deaths?” Gelpi, Feaver, and Reiºer report that 52 percent of the respondents
answered “much more” or “somewhat more important”; 38 percent answered
“about equally important”; and 6 percent said “somewhat less” or “much
less important.”40

The third example of this school of thought is the 2012 study by Daryl Press,
Scott Sagan, and Benjamin Valentino, which utilizes a set of survey experi-
ments to examine the degree to which the U.S. public has an aversion to using
nuclear weapons. Their study demonstrated that a majority of the U.S. public
based their preferences about the choice of weapons not on whether the
weapon was nuclear or conventional, but rather on its relative effectiveness in
destroying the target. When presented with a hypothetical scenario in which
U.S. intelligence agencies informed the president that al-Qaida was suspected
of building a nuclear weapon in a remote site in Syria, 18.9 percent preferred a
nuclear attack, and 47.9 percent said they would approve of using nuclear
weapons if the president had decided to do so, even when nuclear weapons
were deemed to be of equal effectiveness to conventional weapons. When nu-
clear weapons were deemed to be twice as effective in destroying the target,
however, 51.4 percent of the public preferred a nuclear strike and approval rat-
ings increased to 77.2 percent.41 Moreover, the majority of respondents who
opposed using nuclear weapons reported that they did so primarily for fear
of setting a precedent that might encourage the use of such weapons in the
future against the United States or its allies, not because of moral concerns.
Press, Sagan, and Valentino conclude, “[F]or most Americans, the inhibitions
against using nuclear weapons are relatively weak and decidedly not subject
to a taboo.”42

There were three limitations, however, of the Press, Sagan, and Valentino
study. First, to measure the strength of the nuclear taboo per se (and avoid con-
ºating the taboo with an aversion to killing large numbers of civilians), the ex-
periment held the number of expected fatalities in the attack constant and
relatively low, at 1,000 noncombatants killed. Although the results showed
that most Americans were willing to use nuclear weapons against a terrorist
target, the study could not assess the degree to which that support would drop
if larger numbers of civilians in Syria had been expected to be killed in the at-
tack.43 Second, the nature of the enemy—in particular, a terrorist organization
that had attacked the United States—may have inºuenced the public support

40. Ibid., p. 257.
41. Press, Sagan, and Valentino, “Atomic Aversion,” p. 199.
42. Ibid., p. 202.
43. In another experiment dealing with a U.S. attack on an al-Qaida nuclear weapons develop-
ment facility in Syria, however, Press, Sagan, and Valentino found that 52 percent of the American

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International Security 42:1 54

for the U.S. nuclear attack. Many Americans may have been willing to use nu-
clear weapons against al-Qaida, but the study did not examine whether they
would be willing to use nuclear weapons against a foreign state, as the United
States did in World War II. Finally, unlike in World War II, when civilians and
civilian infrastructure were the targets of many bombing campaigns, the civil-
ians killed in the attack against al-Qaida were described in the study as
unintended collateral damage.

Hiroshima in Iran Experiments

To test the alternative theories concerning U.S. public opinion, nuclear weap-
ons use, and noncombatant immunity, we designed a set of survey experi-
ments focused on a contemporary conºict with Iran.44 The experiments asked
subjects to consider a scenario in which Iran attacked the United States ªrst
and in which the president was presented with two options: (1) to send
ground troops to capture Tehran, which would lead to large-scale U.S. military
fatalities; or (2) to attack a major Iranian city, deliberately killing civilians,
in the effort to shock the Iranian government into accepting unconditional
surrender. The three theoretical approaches described above lead to different
hypotheses about how a representative sample of the U.S. public would re-
spond if asked about the potential ªrst use of nuclear weapons against Iran, a
country that Americans have negative feelings about today.45 Tannenwald
argues that the nuclear taboo has “qualities such as absoluteness, unthinking-
ness, and taken-for-grantedness.”46 If the nuclear taboo thesis is correct, there-
fore, the majority of Americans should oppose the hypothetical U.S. nuclear
attack against Iran. If Pinker, Ward, and Crawford are correct and the U.S. pub-
lic has deeply internalized the noncombatant immunity norm, then the major-
ity of Americans should also oppose the use of both nuclear and conventional

public was willing to approve of a nuclear strike that killed 25,000 foreign noncombatants. See
ibid.
44. For prominent examples of the use of survey experiments in international relations, see Mi-
chael Tomz, “Domestic Audience Costs in International Relations: An Experimental Approach,”
International Organization, Vol. 61, No. 4 (Fall 2007), pp. 821–840, doi:10.1017/S0020818307070282;
Michael R. Tomz and Jessica L.P. Weeks, “Public Opinion and the Democratic Peace,” American Po-
litical Science Review, Vol. 107, No. 4 (November 2013), pp. 849–865, doi:10.1017/S0003055413000488;
and Joshua D. Kertzer et al., “Moral Support: How Moral Values Shape Foreign Policy Attitudes,”
Journal of Politics, Vol. 76, No. 3 (July 2014), pp. 825–840, doi:10.1017/S0022381614000073.
45. A Pew poll administered in April 2015, two months prior to our survey, found that 76 percent
of Americans held very or somewhat unfavorable opinions of Iran. Only 14 percent held favorable
or somewhat favorable views. See “Pew Global Attitudes Project Poll, April 2015” (Washington,
D.C.: Pew Global Attitudes Project, 2015).
46. Tannenwald, The Nuclear Taboo, p. 11.

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Revisiting Hiroshima in Iran 55

bombing when it is designed to kill a large number of Iranian civilians. If the
arguments that Americans prioritize winning the war and saving the lives of
U.S. soldiers are valid, however, the majority of Americans should support the
use of nuclear weapons or conventional weapons against Iranian civilians in
the scenarios described in the survey experiment. If this ªnal thesis is correct,
moreover, it suggests that there has been relatively little change in U.S. public
opinion about using nuclear weapons or killing noncombatants since 1945.

We contracted a leading political polling ªrm, YouGov, to administer our
survey experiments to a sample of U.S. citizens older than 18. The polling was
conducted from July 23 to July 30, 2015, among 780 respondents selected from
individuals who registered to participate in YouGov internet surveys, with the
data weighted by YouGov to reºect the demographic composition of the U.S.
public. YouGov utilizes a technique called “sample matching” to approximate
a representative sample.47 Starting with a panel of opt-in participants, YouGov
draws a stratiªed sample matched to the key demographic characteristics of
the U.S. population.48 This sampling technique is relatively new compared to
traditional equal probability random sampling, but it is becoming increasingly
popular for use in academic research applications, and its performance has
been shown to meet or exceed that of surveys based on more traditional
telephone polling techniques.49

experiment design

Unlike public opinion polls that inquire about actual wars, a survey experi-
ment allows us to construct hypothetical scenarios in which we can hold rele-
vant facts about the war constant (e.g., the causes of the war or the identity of
the enemy) while varying only one aspect of the conºict (e.g., the number
of noncombatants killed or the kind of weapons used). This design enables us
to isolate the effects of different levels of expected noncombatant deaths and

47. All the results presented in this article are weighted using survey weights provided by
YouGov. Observations were weighted to match the age, gender, race, and education statistics of
the American population from the American Community Survey.
48. For more information on YouGov’s sample matching technique, see Douglas Rivers and Delia
Bailey, “Inference from Matched Samples in the 2008 US National Elections,” in 2009 JSM proceed-
ings (Alexandria, Va.: American Statistical Association, 2009), pp. 627–639.
49. Robert P. Berrens et al., “The Advent of Internet Surveys for Political Research: A Comparison
of Telephone and Internet Samples,” Political Analysis, Vol. 11, No. 1 (Winter 2003), pp. 1–22,
doi.org/10.1093/pan/11.1.1; David Sanders et al., “Does Mode Matter for Modeling Political
Choice?” Political Analysis, Vol. 15, No. 3 (July 2007), pp. 257–285, doi:10.1093/pan/mpl010; David
S. Yeager et al., “Comparing the Accuracy of RDD Telephone Surveys and Internet Surveys Con-
ducted with Probability and Non-Probability Samples,” Public Opinion Quarterly, Vol. 75, No. 4
(Winter 2011), pp. 1–39, doi:10.1093/poq/nfr020; and Stephen Ansolabehere and Brian F.
Schaffner, “Does Survey Mode Still Matter? Findings from a 2010 Multi-Mode Comparison,” Polit-
ical Analysis, Vol. 22, No. 3 (2014), pp. 285–303, doi:10.2139/ssrn.1868229.

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International Security 42:1 56

the effects of conventional versus nuclear bombing on the U.S. public’s ap-
proval of attacks.

All the stories used in our experiments are presented in the online appen-
dix.50 Each respondent read a mock news article that reported that the United
States had placed severe sanctions on Iran in response to allegations that the
Tehran government had been caught violating the terms of the 2015 Joint
Comprehensive Plan of Action (colloquially known as the Iran Nuclear Deal).
In response, Iran attacked a U.S. aircraft carrier in the Persian Gulf, killing
2,403 military personnel (the same number killed in the Pearl Harbor attack,
though that is not mentioned in the story). As described in the mock news
story, “U.S. forces retaliated immediately with large-scale airstrikes that de-
stroyed all of Iran’s nuclear infrastructure, air defenses, and all Iranian Air
Force bases and planes. When Iran rejected the United States’ demand for
the ‘immediate and unconditional surrender’ of the Iranian government, the
President ordered a ground invasion by U.S. Marines and Army forces de-
signed to destroy the Iranian military and replace the government in Iran.”
The story then reported that the invasion eventually stalled after several
months of ªghting and 10,000 U.S. military fatalities.

Subjects next read that the Joint Chiefs of Staff had presented the president
with two options to end the war. The ªrst option was to continue the land in-
vasion to capture Tehran and compel the Iranian government to surrender.
The second option was to “shock” the Iranian government into accepting un-
conditional surrender by dropping a single nuclear weapon on Mashhad,
Iran’s second-largest city. The article stated that a weapon would be targeted
“directly on Mashhad . . . in the effort to undermine civilian support for the
war and pressure the Iranian government to surrender.” Thus, it was clear that
the bombing was a direct violation of the principle of noncombatant immunity
and had no military target. Holding the estimated number of U.S. military fa-
talities in a continued ground invasion at 20,000, we varied the number of
Iranian noncombatants expected to be killed in the attack on Mashhad from
100,000 to 2 million to measure the degree to which the U.S. public would be
willing to use nuclear weapons and violate the principle of distinction (or non-
combatant immunity) in a scenario similar to the Paciªc War in 1945. We also
included a third condition in which 100,000 Iranian noncombatants were esti-
mated to be killed in a conventional bombing attack. The purpose of this con-
dition was to determine how the use of nuclear versus conventional bombing
would affect U.S. public attitudes about targeting large numbers of noncomba-

50. See doi:10.7910/DVN/9XHAPW/.

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Revisiting Hiroshima in Iran 57

tants. This condition thus provides a direct measure of the depth of the pub-
lic’s support for the noncombatant immunity norm compared to its aversion
toward the use of nuclear weapons.

Because the U.S. military today is so much smaller than it was in World
War II, we could not realistically replicate the conditions of August 1945 in our
news story. In 1945, estimates of U.S. military fatalities in an invasion of Japan
varied signiªcantly—ranging from as low as 20,000 to as high as 300,000—
depending on estimates about where the invasion would occur and how long
the war was expected to last before Japan surrendered, as well as who was
making the calculations.51 We chose an estimate of 20,000 U.S. military fatali-
ties in the march to Tehran in our stories for two reasons. First, it was a more
realistic number for a potential war with Iran today. Second, we compared the
overall size of the U.S. military today (approximately 1.5 million) to that of
the U.S. armed services at the end of World War II (approximately 12 million),
and calculated that 20,000 military fatalities today would fall into the propor-
tional midrange of estimated fatalities in 1945.

For each of these scenarios, we posed the following questions to respon-
dents: “Given the facts described in the article, if you had to choose between
launching the strike against the Iranian city or continuing the ground war
against Iran, which option would you prefer?” and “Regardless of which op-
tion you preferred, if the United States decided to conduct the strike against
the Iranian city, how much would you approve or disapprove of that deci-
sion?” We asked about the personal preferences of respondents to help us un-
derstand their beliefs about what is ethical and appropriate military behavior,
which reºects how well or poorly they have internalized the principles of just
war doctrine. We also asked about respondents’ willingness to approve nu-
clear and conventional bombing attacks, because that is a better measure of
their willingness to support presidential decisions concerning such attacks.
Approval rates may also be more relevant from a policy perspective, given that
political leaders usually focus on estimates of future public attitudes, presum-

51. For a review of the estimates, see J. Samuel Walker, “Historiographical Essay: Recent Litera-
ture on Truman’s Atomic Bomb Decision—A Search for Middle Ground,” Diplomatic History,
Vol. 29, No. 3 (2005), pp. 311–344, doi:10.1111/j.1467-7709.2005.00476.x. Important contributions to
this debate include Barton J. Bernstein, “A Postwar Myth: 500,000 U.S. Lives Saved,” Bulletin of the
Atomic Scientists, Vol. 42, No. 6 (June/July 1986), pp. 38–40, doi:10.1080/00963402.1986.11459388;
Rufus E. Miles Jr., “Hiroshima: The Strange Myth of Half a Million American Lives Saved,” Inter-
national Security, Vol. 10, No. 2 (Fall 1985), pp. 121–140; Richard B. Frank, Downfall: The End of the
Imperial Japanese Empire (New York: Random House, 1999); J. Samuel Walker, Prompt and Utter De-
struction: Truman and the Use of Atomic Bombs against Japan (Chapel Hill: University of North
Carolina Press, 2016); and D.M. Giangreco, “‘A Score of Bloody Okinawas and Iwo Jimas’: Presi-
dent Truman and Casualty Estimates for the Invasion of Japan,” Paciªc Historical Review, Vol. 72,
No. 1 (February 2003), pp. 93–132, doi:10.1525/phr.2003.72.1.93.

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International Security 42:1 58

ably inºuenced by leaders’ explanations of their decisions and the prospects of
success, and not the public opinion preferences expressed before the action.52
The “approval” version of the question, moreover, more directly resembles the
kinds of questions asked in other surveys about President Truman’s decision
to drop the atomic bombs in 1945.

support for nuclear and conventional air strikes

As shown in ªgure 1, a majority of the U.S. public indicated that they would
approve the bombing of Mashhad across all three conditions (columns B,
D, and F). Indeed, Americans explicitly preferred the air-strike option against
Mashhad to the ground assault on Tehran in two of the three conditions (col-
umns A and E). Only in the condition in which 2 million Iranian civilians
would be killed did a slight majority (52.3 percent) prefer the ground attack:
the preference for a nuclear strike against Iranian civilians drops from 55.6 per-
cent (column A) to 47.7 percent (column C) when the number of expected
Iranian civilian fatalities rises from 100,000 to 2 million. Although this differ-
ence is not statistically signiªcant, it suggests that there may be some degree of
aversion to killing extremely large numbers of civilians. Approval rates, how-
ever, remain higher, at close to 60 percent, in both conditions (as seen in col-
umn B and D).

The percentage of Americans who approved of the bombing attack against
Mashhad remained relatively stable regardless of whether conventional or nu-
clear weapons were used, and regardless of whether the attack was estimated
to kill 100,000 or 2 million civilians. The absence of statistically signiªcant dif-
ferences in these latter results across different conditions is precisely what is
substantively and politically signiªcant. That nearly 60 percent of the U.S.
public would approve of a nuclear attack on Iran that would kill 2 million ci-
vilians suggests that the decreasing level of support found in recent polls
about Truman’s decision to drop the bombs in 1945 is a misleading guide to
public opinion about nuclear use today.

That approval ratings were higher than preference ratings in both of our nu-
clear survey conditions (the difference was only statistically signiªcant in the
2 million Iranian deaths condition, columns C and D) suggests that there may
be a small “rally around the bomb” effect, like the common “rally around the
ºag” phenomenon seen after most U.S. decisions to use military force.53 Some

52. See Kenneth A. Schultz, “Domestic Politics and International Relations,” in Walter Carlsnaes,
Thomas Risse, and Beth A. Simmons, eds. Handbook of International Relations, 2nd ed. (London:
Sage, 2012), pp. 485–486; and John Zaller, “Strategic Politicians, Public Opinion, and the Gulf Cri-
sis,” in W. Lance Bennet and David L. Paletz, eds., Taken by Storm: The Media, Public Opinion, and
U.S. Foreign Policy in the Gulf War (Chicago: University of Chicago Press, 1994), pp. 250–274.
53. See Gelpi, Feaver, and Reiºer, Paying the Human Costs of War, pp. 9–10, 236.

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Revisiting Hiroshima in Iran 59

Figure 1. U.S. Public Opinion on Bombing Iran

Question 1 (A, C, E) : “Given the facts described in the article, if you had to choose between launching the
strike against the Iranian city or continuing the ground war against Iran, which option would you prefer?”

Question 2 (B, D, F): “Regardless of which option you preferred, if the United States decided to conduct
the strike against the Iranian city, how much would you approve or disapprove of that decision?”

100%

90%

80%

70%

60%

50%

40%

30%

20%

10%

% prefer air strike

% approve air strike

relevant signiﬁcant differences

A
0.10;

(cid:3)
p

(cid:2)
E^ ; D C*
(cid:3)
**
0.05;
*

(cid:3)

0.01

55.6%

59.3%

47.7%

59.1%

67.3%

63.1%

nuclear air strike (cid:2)
100,000 Iranian civilians dead
(alternative: ground war (cid:2)
20,000 U.S. troops dead)

nuclear air strike

(cid:2)

2,000,000

Iranian civilians dead
(alternative: ground war (cid:2)
20,000 U.S. troops dead)

conventional air strike (cid:2)
100,000 Iranian civilians dead
(alternative: ground war (cid:2)
20,000 U.S. troops dead)

Americans are willing to approve of a presidential decision to use nuclear
weapons even in situations in which they did not personally prefer a nu-
clear response. These results do not appear to be inºuenced by the perception
that the more destructive attack would likely be more effective. When we
asked a follow-up question about whether the air strike was likely to lead to
unconditional surrender, the percentages of respondents who answered posi-
tively were statistically indistinguishable across all conditions.

The conventional bombing scenario also produced noteworthy results. In
column E, 67.3 percent of respondents preferred the conventional bombing at-
tack that deliberately killed 100,000 Iranians, an increase of 11.7 percent from
the percentage of respondents who preferred the nuclear attack in column A
(p (cid:2) 0.07). This result suggests that although these Americans may have been
inºuenced by an aversion to using nuclear weapons against civilians, they
were not averse to intentionally killing civilians with conventional weapons.
That such a large majority of respondents preferred a conventional bombing
attack on a city that would kill 100,000 civilians over a ground assault that

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International Security 42:1 60

would kill 20,000 U.S. soldiers is strong evidence against the theory that
a robust noncombatant immunity norm has been internalized by the U.S.
public today.

To explore the reasons why some Americans are more willing to use conven-
tional weapons than nuclear weapons, we asked all of our subjects two addi-
tional questions. First, “Regardless of which option you preferred, how ethical
or unethical do you think it would be if the United States decided to conduct
the strike against the Iranian city in the situation described in the article?” Sec-
ond, subjects were asked whether they agreed or disagreed with the statement
that “launching the strike against the Iranian city would set a precedent that
would encourage our adversaries to launch similar attacks against America or
our allies in the future.” Our results indicate that a combination of normative
and practical concerns help explain the higher support for the conventional air
strike. Among those who opposed the nuclear strike, 65.1 percent judged it un-
ethical. Among those who opposed the conventional strike, however, the per-
centage that judged it immoral declined only slightly, to 61.6 percent (the
difference was not statistically signiªcant). This suggests that anti-nuclear
norms add little to the aversion to killing civilians. A larger percentage of those
opposed to the strike, however, agreed that it would set a bad precedent both
in the nuclear condition (76.1 percent) and in the conventional condition
(76.8 percent).54

Explaining U.S. Public Support for the Use of Nuclear Weapons

The main conclusions of these survey experiments are clear. The majority of
the U.S. public has not internalized either a belief in the nuclear taboo or a
strong noncombatant immunity norm. When faced with realistic scenarios in
which they are forced to contemplate a trade-off between sacriªcing a large
number of U.S. troops in combat or deliberately killing even larger numbers of
foreign noncombatants, the majority of respondents approve of killing civil-
ians in an effort to end the war. Protecting the lives of U.S. troops was a higher
priority than preventing the use of a nuclear weapon or avoiding the large-
scale conventional bombing of an Iranian city.55

54. The nearly 13-percentage-point difference between those citing ethical or precedential reasons
for opposing the strike in the nuclear scenario versus those doing so in the conventional scenario
was not statistically signiªcant (p (cid:2) 0.14), however, possibly because the small numbers of subjects
who opposed the strike reduced the statistical power of our difference of means tests.
55. In related work focusing on U.S. public opinion on the use of conventional weapons in Af-
ghanistan, we directly measured the public’s willingness to accept increased foreign civilian casu-
alties if doing so would decrease U.S. military casualties. We found that the public was extremely
sensitive to U.S. military losses. Holding the probability of successfully completing the mission

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Revisiting Hiroshima in Iran 61

These survey experiments produce a kind of “historical resonance,” causing
us to consider aspects of U.S. history upon which scholars have not reºected
sufªciently. Such historical evidence both provides indirect support for the ex-
ternal validity of our experiments and generates new insights into the past.
Polling evidence from World War II, for example, suggests that U.S. public
support for killing enemy civilians on a large scale with chemical weapons in-
creased when subjects were cued that using such weapons would save the
lives of U.S. soldiers. In September 1944, for example, only 23 percent of
the U.S. public said they would approve of “using poison gas against Japanese
cities” if it meant “an earlier end of the war in the Paciªc”; yet support surged
to 40 percent in a June 1945 poll in which the prompt stated that a poison gas
attack “against the Japanese” might “reduce the number of U.S. soldiers killed
or wounded.”56

Evidence from polls taken during the 1991 Gulf War also supports this ob-
servation. Two surveys by Gallup, identical except for the phrase “if it might
save the lives of U.S. troops,” prompted the respondents to consider the U.S.
use of an atomic bomb against Iraq. On January 27, 1991, the public was asked:
“Do you favor or oppose using tactical nuclear weapons against Iraq if it
might save the lives of U.S. troops?” On February 14–17, 1991, Gallup posed a
similar question without mentioning the trade-off: “Do you favor or oppose
the U.S. use of tactical nuclear weapons in the Persian Gulf War?” Support for
using nuclear weapons was 45 percent when the trade-off was mentioned, but
only 28 percent when it was not.57 Caution should be used in interpreting
these polls, however, because the ªndings might have been inºuenced by the
fact that the second poll was taken toward the end of the war, when a larger
percentage of the U.S. public was conªdent that the United States was going to
win, making the use of nuclear weapons seem less necessary.58 In addition,
both poll questions explicitly referred to “tactical nuclear weapons,” which

constant, we found that a slight majority of the public was willing to accept the deaths of 5 U.S.
troops if those deaths would avert the deaths of 200 foreign civilians. Nearly three-quarters of
Americans opposed the mission, however, if it would cost 40 U.S. military lives to avert the deaths
of 200 foreign civilians. See Scott D. Sagan and Benjamin A. Valentino, “Just a War Theory? Ameri-
can Public Opinion on Ethics in Military Combat,” Stanford University and Dartmouth College,
2017.
56. Gallup, The Gallup Poll: Public Opinion, 1935–1971, Vol. 1, pp. 521–522. It is important to note,
however, that these polls were conducted at different times during the war, and that the brutality
of the campaign in the Paciªc, especially the large numbers of Americans killed during the
ªghting in early 1945, likely also inºuenced the increased support for using poison gas by
the summer of 1945 as compared to September 1944.
57. George Gallup Jr., The Gallup Poll: Public Opinion, 1991 (Lanham, Md.: Rowman and Littleªeld,
1991), pp. 42, 59.
58. “Questionnaire: U.S. at War with Iraq—Question 15,” 03/22/2003–03/23/2003 (Washington,
D.C.: Gallup, 2003), https://institution.gallup.com/documents/question.aspx?QUESTION(cid:2)143460

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International Security 42:1 62

might have inºuenced the ªndings. Future survey experiments could examine
the interactions among the desire to protect U.S. troops, the perceived prob-
ability of winning the war, and the use of different types of nuclear weap-
ons (tactical weapons used against enemy troops versus bombing of a city,
for example).

demographics

One way to begin explaining the reasons behind the surprising public atti-
tudes revealed in our surveys is to examine the variation in the preferences of
different demographic groups in our sample.

Figure 2 presents the average preferences across the three air-strike scenarios
(100,000 Iranian deaths/nuclear weapons, 2 million Iranian deaths/nuclear
weapons, and 100,000 Iranian deaths/conventional weapons) for ªve major
demographic groups—party identiªcation, age, education, race, and gender—
and one additional characteristic, whether the respondent indicated that he or
she approved of or oppossed the death penalty. Consistent with many other
studies about public opinion and the use of force, we found that Republicans
(69.5 percent) were much more “hawkish” than Democrats (48.4 percent) aver-
aging across the three conditions.59 Americans aged 60 and older were also
signiªcantly more likely to prefer the air-strike options (70.5 percent) than
Americans younger than 60 (51.6 percent), which is also consistent with other
surveys of public opinion and nuclear weapons use.60 All three of these differ-
ences remained statistically signiªcant when all the variables in ªgure 2 were
included in a logistic regression.61

Because these ªndings are consitent with results from other studies on pub-
lic opinion on the use of force, they add conªdence in the external validity of
our survey experiments. There are two surprising ªndings, however, that
deseve more scrutiny. First, why is there so little difference between the
preferences of men and women regarding nuclear use? Second, why is sup-
port or opposition to the death penalty correlated so strongly with nuclear-
use preferences?

women and war

The ªnding that women were no less willing than men to support using
nuclear weapons or conventional weapons in a manner that violated noncom-

&SearchConType(cid:2)1&SearchTypeAll(cid:2)think%20currently%20winning%20war%20persian%20gulf
%20%20%20%20allies%20iraq%20neither%20side\.
59. Gelpi, Feaver, and Reiºer, Paying the Human Costs of War, pp. 67–124.
60. Moore, “A-Bomb Legacy.”
61. Party identiªcation was signiªcant at p (cid:2) 0.063.

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Revisiting Hiroshima in Iran 63

Figure 2. Preference of the U.S. Public for Air Strike by Demographic Subgroup

100%

90%

80%

70%

60%

50%

40%

30%

20%

10%

%
4
.
8
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*
*
*
t
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(cid:3)

0.10;

*
p

(cid:3)

0.05;

(cid:3)

0.001;

***

(cid:3)

0.001

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batant immunity principles was particularly surprising. Women have been
found to be less hawkish than men in most studies on the effect of gender on
support for going to war or using nuclear weapons. Lisa Brandes’s 1994 study
examined all polls from 1945 to 1988 regarding support for the use of nuclear
weapons and found an average 9.1 percent “gender gap” between women and
men regarding approval of U.S. nuclear weapons use.62 Richard Eichenberg’s
broader 2003 study analyzed 486 surveys conducted from 1990 to 2003 and
found that women are less supportive of the use of military force in general
and that the gender gap between men and women concerning support for a
war increases when likely or current U.S. military casualties are mentioned in
the polling questions.63 A rare ªnding to the contrary is reported in Deborah

62. Lisa Brandes, “Public Opinion, International Security, and Gender: The United States and
Great Britain since 1945,” Ph.D. dissertation, Yale University, 1994, p. 166.
63. Richard C. Eichenberg, “Gender Differences in Public Attitudes toward the Use of Force by the
United States, 1990–2003,” International Security, Vol. 28, No. 1 (Summer 2003), pp. 111–112,

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International Security 42:1 64

Brooks and Benjamin Valentino’s 2011 study, which demonstrated that U.S.
women are more hawkish than men in supporting the use of military force
in two scenarios: when the war was described as a humanitarian inter-
vention and when it had the support of a multinational organization, such as
the United Nations, rather than when it was the product of a unilateral na-
tional decision.64

We therefore disaggregated our respondents by gender to examine how
male and female preferences for the air strike varied across our three scenarios.
The ªndings in ªgure 3 demonstrate that women were no less, or even more,
hawkish than men regarding their support for killing large numbers of foreign
civilians to avoid the deaths of U.S. soldiers. Female respondents supported
using the atomic bomb at virtually the same percentages (55.9 percent in col-
umn B, 54.3 percent in column D) regardless of whether 100,000 or 2 mil-
lion Iranian noncombatants were killed. That a higher percentage of U.S.
women (54.3 percent, column D) preferred the atomic attack that killed 2 mil-
lion Iranians than did U.S. men (39.8 percent, column C) is particularly sur-
prising, although given the relatively small cell sizes resulting from dividing
our sample in two, this difference is not signiªcant at conventional levels (p (cid:2)
0.128). In addition, women’s support for the air strike, unlike men’s, did not
increase signiªcantly in the conventional condition. The interaction between
gender and nuclear/conventional conditions, however, was only marginally
(p (cid:2) 0.079). Nevertheless, this ªnding provides some suggestive
signiªcant
and surprising evidence that the aversion to nuclear weapons use may be
stronger among men than women.

This ªnding about gender also provides another example of historical reso-
nance, for it shines a new light on American public opinion during World
War II. The approval rate in August 1945 for dropping the atomic bombs on
Japan among U.S. women (83 percent) was virtually identical to that of
American men (86 percent).65 Further research could focus on identifying the
conditions under which women may be no less willing, or even more willing,
than men to support the use of military force in ways that violate the principle
of noncombatant immunity and kill large numbers of foreign civilians.

doi:10.1162/016228803322427992. See also Dan Reiter, “The Positivist Study of Gender and Inter-
national Relations,” Journal of Conºict Resolution, Vol. 59, No. 7 (October 2015), pp. 1301–1326,
doi:10.1177/0022002714560351.
64. Deborah Jordan Brooks and Benjamin A. Valentino, “A War of One’s Own: Understanding the
Gender Gap in Support for War,” Public Opinion Quarterly, Vol. 75, No. 2 (Summer 2011), pp. 270–
286, doi:10.1093/poq/nfr005.
65. Hadley Cantril and Mildred B. Strunk, Public Opinion, 1935–46 (Princeton, N.J.: Princeton Uni-
versity Press, 1951), p. 20.

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Revisiting Hiroshima in Iran 65

Figure 3. Gender Demographics by Experimental Conditions

Question: “Given the facts described in the article, if you had to choose between launching the
strike against the Iranian city or continuing the ground war against Iran, which option would
you prefer?”

100%

90%

80%

70%

60%

50%

40%

30%

20%

10%

male (prefer air strike)

female (prefer air strike)

(cid:3)

relevant signiﬁcant differences

(cid:2)
E
p
*

(cid:3)

A*, B**, C***, D**, F*
(cid:3)
p

0.05;

0.01;

***

0.10;

(cid:3)

0.001

55.4%

55.9%

39.8%

54.3%

77.6%

58.7%

nuclear air strike (cid:2)
100,000 Iranian civilians dead
(alternative: ground war (cid:2)
20,000 U.S. troops dead)

nuclear air strike

(cid:2)

2,000,000

Iranian civilians dead
(alternative: ground war (cid:2)
20,000 U.S. troops dead)

conventional air strike (cid:2)
100,000 Iranian civilians dead
(alternative: ground war (cid:2)
20,000 U.S. troops dead)

rationaliztion and retribution

The second particularly noteworthy ªnding for our study concerns the strong
positive correlation between whether or not respondents preferred the air-
strike option against Iran and whether they approved the use of the death pen-
alty for convicted murderers in the United States. Across the three scenarios,
Americans who approved of the death penalty were more than twice as likely
to prefer the air strike option (67.3 percent) than were Americans who opposed
the death penalty (31.5 percent).66 This ªnding is consistent with Peter
Liberman’s study of the sources of U.S. public support for the use of torture
and his ªndings about belief in retribution and elite support for the 1991 Gulf
War.67 Rachel Stein has also found that democracies that have maintained the

66. Death penalty support remains strongly signiªcant in a multivariate logistic regression in
which all the demographic characteristics in ªgure 3 are included.
67. Peter Liberman, “Retributive Support for International Punishment and Torture,” Journal of
Conºict Resolution, Vol. 57, No. 2 (April 2013), pp. 285–306, doi:10.1177/0022002712445970; and Pe-

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International Security 42:1 66

death penalty at home are more likey to intiate military conºicts abroad. She
attributes this correlation to beliefs in retribution and revenge that are preva-
lent among some democratic publics.68

What could be the linkage between death penalty support and approval of
nuclear or conventional strikes designed to kill Iranian civilians? Our surveys
reveal a strong pull of retribution and a tendency for individuals to rationalize
the killing of others by claiming that it was their fault. For example, averaging
across all three of our main conditions, a large majority (83.9 percent) of those
who preferred the air-strike option agreed with the following statement:
“Since Iran’s leaders started the war, they are morally responsible for any
Iranian civilian deaths caused by the U.S. strike described in the news story.”
Among respondents who preferred the ground-assault options, only 52.8 per-
cent agreed with that statement. A large majority (68.5 percent) of the respon-
dents who favored the air-strike options also agreed with the statement that
“[b]ecause the Iranian civilians described in the story did not rise up and over-
throw the government of Iran, they must bear some responsibility for the civil-
ian fatalities caused by the U.S. strike described in the news story.” In contrast,
among those who preferred the ground-assault options, only 36.6 percent
agreed with that statement.69

In an open-ended question, we asked respondents to write down the single
most important reason they supported the air strike. The results revealed that
utilitarian calculations about saving U.S. lives and ending the war promptly, as
well as assigning culpability retrospectively, may have motivated subjects’
preference for the air strike. The majority of respondents in all three conditions
who supported the bombing attack cited saving American lives or ending
the war quickly as the reason for their support. That was not unexpected.
What was surprising was the number of Americans who suggested that
Iranian civilians were somehow culpable or were less than human. Justiªca-
tions for the atomic attack that killed 100,000 Iranians included: “Hate the
thought of being the only nation again to launch a nuclear strike, but they
started it and we have lost enough lives”; and “Iran lied again about their nu-
clear facilities, launched an attack on an American warship that killed and hurt
4,000 Americans, and nothing short of complete and total victory over the
lying savages would be acceptable to me.” Justiªcations for killing 2 million

ter Liberman, “Punitiveness and U.S. Elite Support for the 1991 Persian Gulf War,” Journal of
Conºict Resolution, Vol. 51, No. 1 (February 2007), pp. 3–32, doi:10.1177/0022002706294328.
68. Rachel M. Stein, “War and Revenge: Explaining Conºict Initiation by Democracies,” American
Political Science Review, Vol. 109, No. 3 (August 2015), p. 558, doi:10.1017/S0003055415000301.
69. The differences between supporters of the air strikes and supporters of the ground assault on
both of these questions are signiªcant at p (cid:4) 0.000.

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Revisiting Hiroshima in Iran 67

noncombatants included: “They were dancing in the streets and partying in fa-
vor of what happened to the twin towers”; “They hate us and they will violate
any agreement”; “Islam is a religion of fanatics [and] they need to be taught a
lesson”; “Air strike would wipe out any military opponents who will be hid-
ing among civilians”; and “Kill the cockroaches.” Answers given by those who
voted for the conventional attack that was estimated to kill 100,000 Iranian ci-
vilians included: “The article said that Iran attacked the U.S. ship ªrst. The
U.S. is not the aggressor here”; “Iran is ruled by radicals who have no regard
for innocent life”; and “My ªrst choice would be to decapitate the snake—
wipe out the capital—wipe it clean—every living thing.”

retroactive culpability

The experiments of Stanley Milgram and Albert Bandura focused attention on
how often and easily individuals rationalize their violence against others by
retrospectively insisting to themselves that the victims deserved to be pun-
ished. Milgram concluded after his famous obedience experiments “that many
subjects harshly devalue the victim as a consequence of acting against him. . . .
Once having acted against the victim, these subjects found it necessary to view
him as an unworthy individual, whose punishment was made inevitable by
his own deªciencies of intellect and character.”70 Bandura similarly notes that
“blaming one’s adversaries . . . can serve self-exonerative purposes. In this pro-
cess, people view themselves as faultless victims driven to injurious conduct
by forcible provocation. Punitive conduct is, thus, seen as a justiªable defen-
sive reaction to belligerent provocations.”71

We found evidence for this phenomenon in our experiments. We asked all
respondents the following question: “Please rate your feelings toward the fol-
lowing countries, with one hundred meaning a very warm, favorable feeling,
zero meaning a very cold, unfavorable feeling, and ªfty meaning not particu-
larly warm or cold. You can use any number from zero to one hundred. The
higher the number the more favorable your feelings are toward that country.”
Averaging again across all three treatments, we found that the subjects who

70. Stanley Milgram, Obedience to Authority: An Experimental View (New York: Harper and Row,
1974), p. 10.
71. Albert Bandura, “Moral Disengagement in the Perpetration of Inhumanities,” Personality and
Social Psychology Review, Vol. 3, No. 3 (August 1999), p. 203, doi:10.1207/s15327957pspr0303_3. See
also Linda Simon, Jeff Greenberg, and Jack Brehm, “Trivialization: The Forgotten Mode of Disso-
nance Reduction,” Journal of Personality and Social Psychology, Vol. 68, No. 2 (February 1995), p. 247,
doi:10.1037/0022-3514.68.2.247; and Thomas Gilovich, Victoria Husted Medvec, and Serena Chen,
“Commission, Omission, and Dissonance Reduction: Coping with Regret in the ‘Monty Hall’
Problem,” Personality and Social Psychology Bulletin, Vol. 21, No. 2 (February 1995), pp. 182–190,
doi:10.1177/0146167295212008.

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International Security 42:1 68

approved of the air strike rated Iran 19.3 out of 100, more than 15 points lower
than subjects who opposed the strike.72 We do not know from this evidence,
however, which way the causal arrow moves—did respondents support the
air strikes because they have more negative feelings about Iran compared to
ground war supporters, or do air-strike supporters prefer that option for other
reasons and then retrospectively justify their decision by feeling more nega-
tively about Iran? We can, however, see evidence of how the extent of killing in
an air strike retroactively inºuences the respondents’ feelings about Iranians
when one compares the “thermometer scores” of the two different sets of re-
spondents who approved of the different nuclear attacks. The 55.6 percent
who preferred the air strike that killed 100,000 Iranians gave Iran a 19.4 out of
100 mean score, whereas those who opposed the strike rated Iran 28.6. In the
condition in which 2 million Iranian civilians would be killed by the strike,
the 47.7 percent who preferred the air strike gave Iran a 14.5 mean score, and
those who opposed it gave the country a score of 35.7. Thus, the difference
between the thermometer ratings of those who supported and opposed the
strike more than doubled, from 9.2 points in the 100,000 deaths condition to
more than 21 points in the 2 million deaths condition. This effect was mar-
ginally signiªcant (p (cid:2) 0.082). The prospect of killing more noncombatants
appears to have both polarized attitudes toward Iran and intensiªed the hos-
tility of those who supported the strike as a way of justifying the large number
of deaths.

This kind of assignment of “retroactive culpability” is common. We can see
it in ªction from the pre-nuclear age and in the history of the ªrst days of the
nuclear age. Leo Tolstoy, in his scathing description of Czar Nicholas in
the novel Hadji Murat, described this phenomenon well: “Nicholas frowned.
He had done much evil to the Poles. To explain that evil he had to be con-
vinced that all Poles were scoundrels. And Nicholas regarded them as such
and hated them in proportion to the evil he had done them.”73 President
Truman, when responding to a letter criticizing his “indiscriminate bombing”
of Japanese cities, also appears to have justiªed his decision by assigning cul-
pability to all Japanese and dehumanizing the victims: “Nobody is more dis-
turbed over the use of Atomic bombs than I am but I was greatly disturbed by
the unwarranted attack by the Japanese on Pearl Harbor and their murder of
our prisoners of war. The only language they seem to understand is the one
we have been using to bombard them. When you have to deal with a beast you
have to treat him as a beast.”74

72. The difference was signiªcant at p (cid:3) 0 .0001.
73. Leo Tolstoy, Hadji Murat (New York: Vintage, 2012), p. 71.
74. Correspondence between Harry S. Truman and Samuel McCavert, August 11, 1945, Ofªcial

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Revisiting Hiroshima in Iran 69

According to international law and traditional just war doctrine, only civil-
ians who are making a direct contribution to a government’s war effort can be
treated as combatants and thus liable to attack. Mere political support for a
government is not sufªcient to make a civilian a legitimate military target, and
certainly the failure of a people to overthrow a government is an even less le-
gitimate excuse. There is some support among revisionist just war theorists for
including foreign civilians’ indirect responsibility for contributing to their gov-
ernment’s war effort through political support as a legitimate consideration in
attack decisions.75 Nevertheless, no one argues that leaders and the public
should assign culpability retroactively to justify the killing of civilians. Some
of our respondents, however, appear to have done just that: they viewed Iran
and Iranian civilians as Czar Nicholas did the Poles and “hated them in pro-
portion to the evil that [they] had done them.”

The Keeping-the-Ayatollah Experiment

Whenever one is confronted with two morally repugnant choices, it is prudent
to consider whether other possible courses of action are available, including
revising one’s objectives. Michael Walzer, in his classic Just and Unjust Wars,
criticized the bombing of Hiroshima and Nagasaki from precisely this perspec-
tive: “Americans would accept nothing less than unconditional surrender. The
war aims of the American government required either an invasion of the main
islands, with enormous losses of American and Japanese soldiers and of
Japanese civilians trapped in the war zones, or the use of the atomic bomb.
Given that choice, one might well reconsider those aims.”76

Would the U.S. public accept less than unconditional surrender in a war
with Iran that the Tehran government had started with a “surprise” attack on a
U.S. warship? To explore this question, we constructed an experiment de-
signed to examine how the U.S. public would react if it was also presented
with the option of changing the terms of surrender from unconditional surren-
der to allowing Ayatollah Ali Khamenei to stay as a ªgurehead spiritual leader
without political authority (see ªgure 4). A different representative sample of

File 692-A: Manhattan Project, Truman Papers, Harry S. Truman Library, Independence, Missouri,
https://www.trumanlibrary.org/whistlestop/study_collections/bomb/large/documents/index
.php?documentid(cid:2)11&pagenumber(cid:2)1.
75. See Jeff McMahon, Killing in War (Oxford: Oxford University Press, 2009); and Helen Frowe,
“Self-Defence and the Principle of Non-Combatant Immunity,” Journal of Moral Philosophy, Vol. 8,
No. 4 (2011), pp. 530–546, doi:10.1163/174552411X601058. For a critical review of this perspective,
see Seth Lazar, “Evaluating the Revisionist Critique of Just War Theory,” Daedalus, Vol. 146, No. 1
(Winter 2017), pp. 113–124, doi:10.1162/DAED_a_00426.
76. Michael Walzer, Just and Unjust Wars: A Moral Argument with Historical Illustrations (New York:
Basic Books, 1977), p. 267.

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International Security 42:1 70

Figure 4. Preference of the U.S. Public for a Nuclear Strike or Ground War against Iran

or a Conditional Surrender Deal with Iran’s Ayatollah

Question 1 (A, B): “Given the facts described in the article, if you had to choose between
launching the strike against the Iranian city or continuing the ground war against Iran, which
option would you prefer?”

Question 2 (C, D, E): “If you had to choose between the three options described in the article,
would you refer to launch the strike against the Iranian city, to continue the ground war against
Iran, or to offer to allow the Ayotollah to stay on as spiritual leader without any political power?”

100%

90%

80%

70%

60%

50%

40%

30%

20%

10%

% prefer nuclear strike
% prefer ground war
% prefer Ayotollah deal

55.6%

44.4%

nuclear air strike (cid:2)
100,000 Iranian civilians dead

ground war

20,000 U.S. troops dead

(cid:2)

relevant signiﬁcant differences

A C***; A
(cid:3)
p
0.10;

(cid:2)
^

(cid:2)
p
*

(cid:2)
(cid:2)
E**; B D***; C D***; E D***
(cid:3)
0.001
0.01;

(cid:2)
p
0.05;

***

(cid:3)

40.3%

D
18.8%
nuclear air strike (cid:2)
100,000 Iranian civilians dead

41.1%

ground war

(cid:2)
deal with Ayotollah

20,000 U.S. troops dead

(cid:2)

no deaths

Americans read the same story with the identical ground-assault costs (20,000
U.S. soldiers) and nuclear air-strike costs (100,000 Iranian civilians) as in the
earlier story, but with the following paragraph added:

The President has also been considering a diplomatic option that might bring
the war to an end. In that option, the United States would publically maintain
its demand for unconditional surrender, but privately inform the leadership in
Tehran that if Iran surrenders immediately, Ayatollah Khamenei would be im-
mune from war crime prosecution and would be permitted to remain in a po-
sition as spiritual leader, without any political power, in a new, freely elected
Iranian government. Some high-ranking members of the administration be-
lieve that Iran is now close to surrender and allowing the Ayatollah to con-
tinue to serve in this way might be enough to convince Iran to agree to
surrender immediately.

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Revisiting Hiroshima in Iran 71

It is valuable to understand whether the U.S. public would support or approve
of the dropping of the bomb if there was an expectation that the Iranian gov-
ernment would surrender under this diplomatic compromise option. All sub-
jects who read this story were then asked, “If you had to choose between the
three options described in the article, would you prefer to launch the strike
against the Iranian city, to continue the ground war against Iran, or to offer
to allow the Ayatollah to stay on as a spiritual leader without any politi-
cal power?”

This experiment attempted roughly to mirror the 1945 history in which
President Truman insisted on the unconditional surrender of Japan in the
Potsdam Declaration, despite having received advice from Secretary of War
Henry Stimson that some kind of guarantee that Emperor Hirohito would not
be put on trial or punished after the war would be needed to get Japan to sur-
render.77 This advice proved prophetic when the Japanese government, after
the destruction of Hiroshima and Nagasaki and the Soviet entry into the war,
signaled that it was ready to surrender but only on the condition that surren-
der did not prejudice “the prerogatives of his majesty (Emperor Hirohito) as a
sovereign ruler.”78 Truman immediately sought to signal the Japanese govern-
ment through the carefully crafted letter drafted by Secretary of State James
Byrnes on August 11 that the emperor would, in fact, not be subject to war
crimes trials and would be permitted to stay on as a ªgurehead leader in
Tokyo. The Byrnes letter, while insisting that the “authority of the emperor”
would be “subject to the Supreme Commander of the Allied Powers,” also
promised that “the ultimate form of government of Japan shall, in accordance
with the Potsdam Declaration, be established by the freely expressed will of
the Japanese people,” which was understood by both Hirohito and Truman as
a signal that the emperor would not be put on trial.79 On August 14, after hav-

77. For scholarly analysis of the debate about the role of the emperor, unconditional surrender
terms, and the Byrnes letter, see Barton J. Bernstein, “Understanding the Atomic Bomb and the
Japanese Surrender: Missed Opportunities, Little-Known Near Disasters, and Modern Memory,”
Diplomatic History, Vol. 19, No. 2 (March 1995), pp. 227–273, doi:10.1111/j.1467-7709.1995.tb00657.x;
Herbert P. Bix, “Japan’s Delayed Surrender: A Reinterpretation,” in Michael J. Hogan, ed., Hiro-
shima in History and Memory (Cambridge: Cambridge University Press, 1996), pp. 90–91; Sean L.
Malloy, Atomic Tragedy: Henry L. Stimson and the Decision to Use the Bomb against Japan (Ithaca, N.Y.:
Cornell University Press, 2008), pp. 120–142; and Tsuyoshi Hasegawa, Racing the Enemy: Stalin,
Truman, and the Surrender of Japan (Cambridge, Mass.: Harvard University Press, 2005), pp. 145–
160, 218–222.
78. See Herbert P. Bix, Hirohito and the Making of Modern Japan (New York: Harper Collins, 2000),
p. 517. Bix notes that to make the Byrnes note more palatable to Hirohito, members of the Peace
Party mistranslated several key words, changing “shall be subject to” to “shall be circumscribed
by.”
79. Letter from U.S. Secretary of State James F. Byrnes to the Secretary of State to the Swiss Chargé
Max Grässli, FRUS: Diplomatic Papers, 1945, Vol. 6: The British Commonwealth, the Far East (Washing-

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International Security 42:1 72

ing been briefed on the contents of the Byrnes letter, and a few days after both
the Soviet Union’s entry into the war and the atomic bombing of Nagasaki,
Hirohito ªnally decided to publicly accept the Allied peace terms.80 On
August 12, when a member of Japan’s imperial family asked Hirohito if the
war would continue if the kokutai (the imperial national polity) could not be
preserved, the emperor replied “of course.”81

President Truman did not discuss the Byrnes letter in his public address an-
nouncing the end of the war in which he insisted that the ªnal Japanese sur-
render constituted “a full acceptance of the Potsdam Declaration which
speciªed the unconditional surrender of Japan.”82 Truman understood the
public view of Hirohito’s culpability: a poll taken in June 1945 showed strong
support for punishing the emperor for his role in the war: indeed, 11 percent
of the U.S. public favored “keeping him in prison for the rest of his life,” and
33 percent favored executing him.83 It is impossible to know what would have
happened had the United States softened its unconditional surrender terms
earlier. Truman did not express any remorse about the failure to signal the
Japanese about the fate of the emperor until after both bombs had been
dropped, simply stating in his diary on August 10: “They wanted to make a
condition precedent to the surrender. Our terms are ‘unconditional.’ They
wanted to keep the Emperor. We told‘em we’d tell’em how to keep him, but
we’d make the terms.”84 Only Secretary of War Stimson, who had earlier advo-
cated for softening the unconditional surrender terms, would later express his
belief “that history might ªnd that the United States, by its delay in stating its
position, had prolonged the war.”85

The results presented above suggest that the majority of the U.S. public has
not foresworn nuclear weapons or rejected the targeting of civilians during

ton, D.C.: GPO, 1969), pp. 631–632, http://digicoll.library.wisc.edu/cgi-bin/FRUS/FRUS-idx?type
(cid:2)turn&entity(cid:2)FRUS.FRUS1945v06.p0644&id(cid:2)FRUS.FRUS1945v06&isize(cid:2)M. Truman was later
asked in an interview, “Were there any representations made to the emperor that he would be re-
tained?” Truman answered: “Yes, he was told that he would not be tried as a war criminal and that
he would be retained as emperor.” As quoted in Hasegawa, Racing the Enemy, p. 221.
80. Bix, Hirohito and the Making of Modern Japan, pp. 518–519.
81. Ibid., p. 519.
82. John W. Dower, Cultures of War: Pearl Harbor/Hiroshima/9-11/Iraq (New York: W.W. Norton,
2010), pp. 238–239.
83. “The Quarter’s Polls,” Public Opinion Quarterly, Vol. 9, No. 2 (Summer 1945), p. 246. See also
Memorandum by the Secretary of the Joint Chiefs of Staff, June 18, 1945, FRUS: The Conference of
Berlin (The Potsdam Conference), 1945, Vol. 1 (Washington, D.C.: GPO, 1960), p. 909, https://
history.state.gov/historicaldocuments/frus1945Berlinv01/d598.
84. Robert H. Ferrell, Off the Record: The Private Papers of Harry S. Truman (New York: Harper and
Row, 1980), p. 61.
85. Henry L. Stimson and McGeorge Bundy, On Active Service in Peace and War (New York: Harper
and Brothers, 1947), p. 629. See also McGeorge Bundy, Danger and Survival: Choices about the Bomb
in the First Fifty Years (New York: Random House, 1988), pp. 82–88.

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Revisiting Hiroshima in Iran 73

war since World War II. Might the public be more open today, however, to the
kind of deal that Truman and Stimson were willing to make in 1945? Would
the U.S. public support such a diplomatic compromise today, if it could
avoid either an atomic attack on Iran or a costly ground assault on Tehran to
end a war?

Recall from ªgure 4 that when respondents read that the president was con-
sidering only two options in the ªrst experiment—and asked which they pre-
ferred—55.6 percent (column A) preferred launching a nuclear strike that
would result in 100,000 Iranian civilian deaths, whereas 44.4 percent (col-
umn B) preferred a ground attack that would result in the deaths of 20,000 U.S.
soldiers. When respondents were presented with a third option (the deal in-
volving the Ayatollah Khamenei), however, the percentage preferring the nu-
clear strike decreased to 40.3 percent (column C), and only 18.6 percent
(column D) now preferred the conventional ground assault. In short, 41.1 per-
cent (column E) of the public was willing to permit the ayatollah to remain as a
spiritual leader in Iran if that meant ending the war without further U.S. mili-
tary fatalities or Iranian civilian deaths. It is important to emphasize that the
majority of those now supporting the diplomatic option appear to have shifted
from the camp that had preferred the conventional ground-attack option in the
scenario without the diplomatic option.

Most important, 40.3 percent (column C) of the public still preferred the nu-
clear attack that would kill 100,000 Iranian civilians rather than compromise
on unconditional surrender. This ªnding is particularly disturbing. That
55.6 percent of the U.S. public preferred and 59.3 percent approved of killing
100,000 Iranian civilians to save 20,000 U.S. soldiers may not be surprising to
many. It suggests, after all, that Americans place a much higher value on sav-
ing U.S. soldiers’ lives than on sparing the lives of foreign noncombatants.
However, the ªnding that more than 40 percent of Americans are willing to
kill 100,000 Iranians to avoid permitting Ayatollah Khamenei to stay in a posi-
tion of spiritual
leader without political authority after the hypothetical
war suggests that something other than pure utilitarian assessments of the
value of American versus Iranian lives inºuenced the assessment of options in
this scenario.86

On the one hand, when asked, for example, if they agreed with the state-
ment, “If the U.S. agrees to allow the Ayatollah to stay on as a spiritual leader

86. Interestingly, though the availability of the diplomatic option had a signiªcant effect on the
public’s preferences, it had virtually no effect on approval of the nuclear strike. In the scenario
without the diplomatic option (depicted in ªgure 1), 59 percent of respondents approved of the
nuclear attack. When presented with the third diplomatic option regarding Ayatollah Khamenei,
57 percent said that they would have approved of the nuclear strike if the president had chosen it.

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International Security 42:1 74

without any political power, other adversaries will doubt the credibility of the
United States to carry out its threats in the future,” 70.1 percent of those who
preferred the nuclear strike said yes. On the other hand, when asked whether
they agreed with the statement that “[b]ecause the Iranian civilians described
in the story did not rise up and overthrow the government of Iran, they must
bear some responsibility for the civilian fatalities caused by the U.S. strike de-
scribed in the news story,” 77.9 percent of those who preferred the strike an-
swered yes. Moreover, 40.2 percent of those who preferred the nuclear strike
also said they thought the deal would end the war. So, those subjects did not
choose the nuclear strike based on a perceived lack of effectiveness of the dip-
lomatic option.

These ªndings warn us, as Liberman has noted, that “[p]eople tend to
downplay or underestimate their own retributiveness.” “Survey respondents,”
he writes, “are far more willing to justify their support of the death penalty in
terms of a ‘life for a life’ or ‘punishment ªts the crime’ than as ‘retribution’
or ‘vengeance,’ even though these are identical concepts. Out of wishful
thinking or social desirability bias, it seems, people habitually exaggerate
the instrumental purposes of punishments that they actually favor for retri-
butive reasons.”87

Some respondents’ answers to the question of why they supported the nu-
clear attack, despite the existence of a diplomatic option to end the war, are
more candid and reveal the depth of feelings of retribution and hatred. Rea-
sons for supporting the nuclear attack in this condition included answers such
as: “They visously [sic] attacked America, and starting [sic] a war by killing
many Americans and no more Americans should have to die for a someone
else’s hateful acts”; “Wipe them out, all leaders and followers”; “Bomb the hell
out of them; They’re all barbaric animals anyways, dirty muslim [sic] lives are
less valuable then [sic] American lives”; “Don’t stop until they are dead”; and
“They attacked us ªrst, therefore, show no mercy. But, the bomb should be
dropped on Tehran.”

Recall that 22.7 percent of the U.S. public in 1945 said that they wished that
President Truman had dropped many more bombs before Japan had a chance
to surrender. Few Americans today express such views about Japan, but it
would be falsely reassuring to believe that such sentiments are anachronistic,
produced by the long and deadly ªghting in the Paciªc War. Our experiments
reveal a darker truth. As in 1945, a signiªcant portion of the U.S. public today
would want to use nuclear weapons against an enemy that attacked the
United States even when presented with a diplomatic option to end the war.

87. Liberman, “Punitiveness and U.S. Elite Support for the 1991 Persian Gulf War,” p. 6.

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Revisiting Hiroshima in Iran 75

For this signiªcant portion of the U.S. public, there is no atomic aversion.
Atomic attraction prevails.

Conclusion

The novel survey experiments described in this article, by re-creating
the trade-off between an atomic attack and the risk to the lives of U.S. sol-
diers that the United States faced at the end of World War II, produced many
surprising ªndings. The U.S. public’s willingness to use nuclear weapons and
deliberately kill foreign civilians has not changed as much since 1945 as many
scholars have assumed. Contrary to the nuclear taboo thesis, a majority of
Americans are willing to support the use of a nuclear weapon against an
Iranian city killing 100,000 civilians. Contrary to the theory that Americans ac-
cept the noncombatant immunity norm, an even larger percentage of the U.S.
public was willing to kill 100,000 Iranian civilians with conventional weapons.
Women are as hawkish as men and, in some scenarios, are even more willing
to support the use of nuclear weapons. Belief in the value of retribution is
strongly related to support for using nuclear weapons, and a large majority of
those who favor the use of nuclear weapons against Iran stated that the Iranian
people bore some of the responsibility for that attack because they had not
overthrown their government.

Future research will be necessary to determine whether these ªndings hold
only for Americans or whether they are generalizable to the citizens of other
countries. The U.S. public may be an outlier with regard to supporting nuclear
weapons use, as it is an international outlier with respect to support for the
death penalty. A 2016 public opinion poll in the United Kingdom, for example,
found that approval ratings for President Truman’s decision to drop the
atomic bombs on Japan are much lower than those in the United States (28 per-
cent in the United Kingdom compared with 45 percent in the United States).88
It would be especially useful to focus on public attitudes about nuclear weap-
ons use among key U.S. friends and allies. It would be valuable to know, for
example, how the Israeli, the British, or the French public views potential uses
of nuclear weapons in scenarios, such as those analyzed above, in which they
are contemplating trade-offs between saving their own soldiers versus killing
foreign noncombatants. Future survey experiments could provide new infor-
mation not only about allied publics’ views regarding potential uses of their

88. Will Dahlgreen, “America ‘Was Wrong’ to Drop the A-Bomb—British Public” (London:
YouGov, May 19, 2016), https://yougov.co.uk/news/2016/05/19/america-was-wrong-drop-
bomb-public/.

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International Security 42:1 76

own nuclear arsenals, but also about whether these publics would support
or oppose the use of U.S. nuclear weapons in speciªc scenarios, which could
be an important consideration for U.S. leaders contemplating nuclear use.

Further research will also be needed to determine whether the U.S. public
maintains these priorities under other wartime or crisis scenarios. It is possible
that the widespread hostility that the American public harbors toward Iran
helped produce these ªndings, and in a war against other foreign powers
against which there is less hostility, there would be less willingness to use nu-
clear weapons or kill noncombatants. Still, it seems likely that the U.S. public
would be hostile toward the population of any foreign state that is at war with
the United States. Yet it is also possible that the U.S. public would feel differ-
ently about killing foreign civilians in a war that the United States initiated in-
stead of one sparked by an enemy surprise attack. It would also be valuable to
know how strongly U.S. public attraction to nuclear use in our experiments
was inºuenced by the fact that the United States’ adversary in the war was an
Islamic state in the Middle East. One could explore these effects through new
experiments that vary the religious and racial identity of potential victims of a
U.S. nuclear attack.89

We have been careful in these experiments not to “prime” the respondents
in ways that might bias the results. For example, in our stories, we did not
mention the possible environmental effects of nuclear weapons. We described
the victims as “civilians” rather than “innocent women and children.” We
mentioned only “immediate deaths and long-term fatalities” from the nuclear
attack, and did not describe the gruesome details of fatal burns or radiation
sickness. We did not raise the possibility that an attack targeted against a city
as a “shock strategy” would violate both the laws of armed conºict and U.S.
nuclear weapons employment guidance, and thus would also likely be op-
posed by many senior U.S. military leaders.90 Nor did we expose subjects to
cues from political elites who opposed the bombing.91 All these factors could

89. For an analysis of how the racial and ethnic composition of victims inºuenced civilian target-
ing in past wars, see Tanisha M. Fazal and Brooke C. Greene, “A Particular Difference: European
Identity and Civilian Targeting,” British Journal of Political Science, Vol. 45, No. 4 (October 2015),
pp. 829–851, doi:10.1017/S0007123414000210.
90. One this issue, see C. Robert Kehler, “Nuclear Weapons & Nuclear Use,” Daedalus, Vol. 145,
No. 4 (Fall 2016), pp. 50–61, doi:10.1162/DAED_a_00411; Jeffrey G. Lewis and Scott D. Sagan, “The
Nuclear Necessity Principle: Making US Targeting Policy Conform with Ethics & the Laws of
War,” Daedalus, Vol. 145, No. 4 (Fall 2016), pp. 62–74, doi:10.1162/DAED_a_00412; and Theodore T.
Richard, “Nuclear Weapons Targeting: The Evolution of Law and U.S. Policy,” Military Law Review,
Vol. 224, No. 4 (2017), pp. 862–978, https://ssrn.com/abstract(cid:2)2924907.
91. Research shows that elite cues have a major impact on U.S. public opinion regarding foreign
policy decisions. See, for example, Adam J. Berinsky, “Assuming the Costs of War: Events, Elites,
and American Public Support for Military Conºict,” Journal of Politics, Vol. 69, No. 4 (November

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Revisiting Hiroshima in Iran 77

inºuence public support for or opposition to the use of nuclear weapons or vi-
olations of the noncombatant immunity norm in the real world and should be
studied in the future.

In the ªnal analysis, our survey experiments cannot tell us how future U.S.
presidents and their top advisers would weigh their options if they found
themselves in a conºict in which they faced a trade-off between risking large-
scale U.S. military fatalities and killing large numbers of foreign noncomba-
tants. Nevertheless, these surveys do tell us something unsettling about the
instincts of the U.S. public concerning nuclear weapons and noncombatant im-
munity. When provoked, and in conditions where saving U.S. soldiers is at
stake, the majority of Americans do not consider the ªrst use of nuclear weap-
ons a taboo, and their commitment to noncombatant immunity in wartime is
shallow. Instead, a majority of Americans prioritize winning the war quickly
and saving the lives of U.S. soldiers, even if that means killing large numbers
of foreign noncombatants.

Both just war doctrine and the laws of armed conºict require leaders and
soldiers to make active efforts and accept risks in war to avoid the deaths of
foreign civilians. Michael Walzer’s “doctrine of double intention,” for exam-
ple, requires that soldiers not just intend to attack only legitimate military tar-
gets, but that they also take active measures to minimize unintended collateral
damage, including accepting at least some risk to themselves.92 With respect to
international law, Article 57 of the Geneva Protocol I demands that all signato-
ries “take all feasible precautions in the choice of means and methods of attack
with a view to avoiding, and in any event to minimizing, incidental loss of ci-
vilian life.”93 Although the “principle of feasible precaution” may require mili-
tary professionals to take some personal risk to protect noncombatants or
require political leaders to take some risk of the loss of soldiers to protect for-
eign noncombatants, there is no agreement on the proper risk ratio. How
many soldiers’ lives on one’s own side is it appropriate to risk to reduce the
risk of the unintended killing of foreign noncombatants?94

2007), pp. 975–997, doi:10.1111/j.1468-2508.2007.00602.x; and John R. Zaller, “Elite Leadership of
Mass Opinion: New Evidence from the Gulf War,” in Bennett and Paletz, Taken by Storm, pp. 186–
209.
92. Walzer, Just and Unjust Wars, pp. 152–157, 318–319.
93. Adam Roberts and Richard Guelff, Documents on the Laws of War (New York: Oxford Univer-
sity Press, 2000), pp. 452–453.
94. For further discussion on risk transfer and force protection, see Crawford, Accountability for
Killing; Steven P. Lee, Ethics and War: An Introduction (Cambridge: Cambridge University Press,
2012), pp. 218–222; David Luban, “Risk Taking and Force Protection,” in Yitzhak Benbaji and Na-
omi Sussmann, eds., Reading Walzer (London: Routledge, 2013), pp. 277–301; Ziv Bohrer and Mark
J. Osiel, “Proportionality in Military Force at War’s Multiple Levels: Averting Civilian Casualties
vs. Safeguarding Soldiers,” Vanderbilt Journal of Transnational Law, Vol. 46, No. 3 (2013), pp. 747–

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International Security 42:1 78

We were not surprised by the ªnding that most Americans place a higher
value on the life of an American soldier than the life of a foreign noncomba-
tant. What was surprising, however, was the radical extent of that preference.
Our experiments suggest that the majority of Americans ªnd a 1:100 risk ratio
to be morally acceptable. They were willing to kill 2 million Iranian civilians to
save 20,000 U.S. soldiers. One respondent who approved of the conventional
air strike that killed 100,000 Iranian civilians candidly expressed even more ex-
treme preferences regarding proportionality and risk ratios, while displacing
U.S. responsibility for the attack onto the Iranian people: “I would sacriªce
1 million enemies versus 1 of our military. Their choice, their death.”

U.S. political leaders have, in some important cases in the past, been aware
of public sentiments regarding retribution and revenge and have used the
threat of public pressure in favor of nuclear attacks to add credibility to thinly
veiled nuclear threats. President George H.W. Bush, for example, wrote to
Iraqi President Saddam Hussein in January 1991 that “the United States will
not tolerate the use of chemical or biological weapons. . . . The American peo-
ple would demand the strongest possible response.”95 Secretary of State James
Baker ampliªed the message in a meeting with Iraqi Foreign Minister Tariq
Aziz: “If the conºict starts, God forbid, and chemical or biological weapons are
used against our forces, the American people would demand vengeance. We
have the means to exact it.”96 Although scholars now know that the Bush ad-
ministration had already decided not to use nuclear weapons to respond to
any Iraqi chemical or biological weapons attack, Saddam Hussein did not
know that and took the threat of U.S. nuclear weapons use seriously.97 Our
survey experiments demonstrate that such public pressures to use nuclear
weapons are not fanciful and should be taken seriously by both U.S. leaders

822; Martin Shaw, The New Western Way of War: Risk-Transfer War and Its Crisis in Iraq (Cambridge:
Polity, 2005); and Anna Geis, Harald Müller, and Niklas Schörnig, “Liberal Democracies as Mili-
tant ‘Forces for Good’: A Comparative Perspective,” in Geis, Müller, and Schörnig, eds., The Mili-
tant Face of Democracy: Liberal Forces for Good (New York: Cambridge University Press, 2013),
pp. 325–326.
95. Weekly Compilation of Presidential Documents, January 12, 1991, Vol. 21, No. 3 (Washington, D.C.:
Ofªce of the Federal Register, National Archives and Records Administration, 1991), p. 44.
96. James A. Baker III, with Thomas M. DeFrank, The Politics of Diplomacy: Revolution, War, and
Peace, 1989–1992 (New York: G.P. Putnam’s Sons, 1995), p. 359.
97. Bush’s decision not to use nuclear weapons even if Iraq used chemical weapons was revealed
in George Bush and Brent Scowcroft, A World Transformed (New York: Alfred A. Knopf, 1998),
p. 463. For analyses about Saddam’s plans and perceptions, based on Iraqi war records including
Saddam’s tapes, see Paul C. Avey, “Who’s Afraid of the Bomb? The Role of Nuclear Non-Use
Norms in Confrontations between Nuclear and Non-Nuclear Opponents,” Security Studies, Vol. 24,
No. 4 (Winter 2015), pp. 563–596, doi:10.1080/09636412.2015.1103128; and Benjamin Buch and
Scott D. Sagan, “Our Red Lines and Theirs: New Information Reveals Why Saddam Hussein
Never Used Chemical Weapons in the Gulf War,” Foreign Policy, December 31, 2013, http://
foreignpolicy.com/2013/12/13/our-red-lines-and-theirs/.

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Revisiting Hiroshima in Iran 79

and any foreign government contemplating war against the United States. In-
deed, these experiments suggest that pressures for escalating violence, includ-
ing a public demand for vengeance and pressure to use nuclear weapons,
extend beyond scenarios in which the United States is responding to nuclear,
chemical, or biological attacks.

Past surveys that show a very substantial decline in U.S. public support for
the 1945 dropping of the atomic bombs are a misleading guide to how the pub-
lic would react if placed in similar wartime circumstances in the future. It is
fortunate that the United States has not faced wartime conditions in the nu-
clear era in which U.S. political leaders and the public had to contemplate such
grave trade-offs.98 Today, as in 1945, the U.S. public is unlikely to serve as a se-
rious constraint on any president who might consider using nuclear weapons
in the crucible of war.

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98. For further discussion of this issue, see Benjamin A. Valentino, “Moral Character or Character
of War? American Public Opinion on Targeting of Civilians in Time of War,” Daedalus, Vol. 145,
No. 4 (Fall 2016), pp. 127–138, doi:10.1162/DAED_a_00417.
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