Evidence of the unthinkable: Experimental wargaming at the nuclear threshold
| Published date | 01 September 2023 |
| DOI | http://doi.org/10.1177/00223433221094734 |
| Date | 01 September 2023 |
| Subject Matter | Regular Articles |
Evidence of the unthinkable: Experimental
wargaming at the nuclear threshold
Andrew W Reddie
School of Information, University of California, Berkeley
Bethany L Goldblum
Department of Nuclear Engineering, University of California, Berkeley
Abstract
Ongoing nuclear modernization programs in Russia, China, and the USA have reopened longstanding debates
among scholars concerning whether tailored nuclear weapons are likely to have destabilizing consequences for
international security. Without data to adjudicate this debate, however, these discussions have remained entirely
theoretical. In this article, we introduce an experimental wargaming platform, SIGNAL, to quantify the effect of
tailored nuclear capabilities on the nuclear threshold in a simulated environment. We then compare these results with
a survey experiment using scenarios related to military basing, cyber operations, and nuclear threats from the
wargame environment. While the survey experiments suggest that the presence of tailored nuclear capabilities
increases the likelihood of conflict escalation, this trend diminishes in the wargaming context. Across both data-
generating processes, we find support for the proposition that lower-yield nuclear weapons are used as a substitute for
their higher-yield counterparts. These results have consequences for recent and ongoing policy debates concerning
strategic posture and the future of arms control. This work also makes methodological contributions to the design
and application of experimental wargaming for social science research, particularly for scenarios where data are
limited or non-existent.
Keywords
experiments, nuclear weapons, wargaming
‘We have no empirical data beyond 1945 about how events
may run if nuclear weapons are used.’—Sir Michael
Edward Quinlan
Introduction
Debates concerning the strategic impact of tailored
nuclear weapons – nuclear weapons designed to produce
custom effects such as a low explosive yield or electro-
magnetic pulse (EMP) effects – have existed throughout
the nuclear age, with some suggesting that they contrib-
ute to stability and others to instability. Nitze, writing
during a period in which a doctrine of massive retaliation
was ascendant, suggested as early as 1955 that adding
tailored nuclear capabilities might reduce the vulner-
ability of the USA to nuclear blackmail by the Soviet
Union (Buzzard, 1956; Nitze, 1956). Ten years later,
McNamara suggested that NATO adopt the doctrine
of flexible response with an emphasis on the role of
theater nuclear weapons to ensure that the USA had
the capability to respond to escalation (Powell, 1988),
and in 1974, the Schlesinger doctrine outlined the uses
of limited nuclear options as counterforce weapons
(Schlesinger, 1975; Burr, 2005). More recently, nuclear
modernizationinRussia,ChinaandtheUSAhas
rekindled academic arguments regarding the opport-
unities and pitfalls associated with tailored nuclear
capabilities (Heginbotham et al., 2017; Podvig, 2018;
Corresponding author:
areddie@berkeley.edu
Journal of Peace Research
2023, Vol. 60(5) 760–776
ªThe Author(s) 2022
Article reuse guidelines:
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DOI: 10.1177/00223433221094734
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Talmadge, 2019). The release of the 2018 Nuclear Pos-
ture Review announcing plans for a new low-yield
nuclear warhead (the W76-2 variant), in particular,
renewed this theoretical debate with some suggesting
that this development would be destabilizing while oth-
ers argued that the capabilities are necessary for stability
(Broad & Sanger, 2016; Narang, 2018; Long, 2018;
Roblin, 2019; Facini, 2020).
However, in the absence of empirical data, how do we
adjudicate these claims? How, if at all, might tailored
nuclear capabilities impact the threshold for nuclear use?
To address these questions, we introduce a first applica-
tion of large-Nexperimental wargaming as a method of
social science inquiry.
Below, we examine the impact of high-precision low-
yield and enhanced-EMP nuclear weapons on the
nuclear threshold using data from the Strategic Interac-
tion Game between Nuclear Armed Lands (SIGNAL)
experimental wargaming platform. Specifically, we com-
pare player behavior and game outcomes with and with-
out these weapons in the arsenal and examine the
likelihood of nuclear use. To benchmark the study, we
compare these results with a more traditional three-
segment survey experiment that uses the same treatment
in scenarios designed to approximate those from the
wargame setting. Our analysis suggests that the inclusion
of tailored nuclear capabilities in an arsenal may increase
the likelihood of nuclear use and substitute for high-yield
nuclear use. This effect was observed with statistical sig-
nificance in the survey setting – an important finding
given the widespread use of survey methods in the field.
Finally, we reflect on the methodological contribution of
the article and the potential applications of experimental
wargaming to behavioral social science and international
relations research.
Tailored nuclear options in theory
A lack of observational data poses a significant challenge
to the empirical examination of nuclear issues (Colby &
Gerson, 2013; Lieber & Press, 2017). As Gartzke,
Kaplow & Mehta (2015) note, the literature often fails
to account for the ‘diverse portfolios of [nuclear] weap-
ons with varying range, destructive power, and other
characteristics’. Scholars have come to rely on theory and
extrapolation from a limited number of cases to examine
the potential effects of adding new capabilities to the
nuclear arsenal (Brodie et al., 1946; Schelling, 1966;
Zagare, 1985; Brewer & Blair, 1979; Powell, 1990;
Larsen & Kartchner, 2014; Acton, 2015; Heimer, 2018).
This scholarship has contributed a number of assertions
related to the nuclear threshold. While some suggest that
the ‘nuclear-ness’ of weapons explains patterns of non-use
(Tannenwald, 1999, 2005), others posit that there remain
conditions under which states may still engage in limited
nuclear war (Larsen & Kartchner, 2014; Freedman &
Michaels, 2019). This leaves us with a central question,
how do nuclear capabilities with tailored effects shape the
likelihood of nuclear use?
In the sections below, we outline two schools of
thought pertaining to the impact of tailored nuclear
weapons on escalation.
Tailored nuclear weapons and stability
Throughout the 1950s and 1960s, proponents of tai-
lored nuclear capabilities outlined the benefits of using
tactical nuclear weapons in a graduated deterrence archi-
tecture rather than in the ‘massive retaliation’ strategy
that represented the orthodoxy of the period (Blackett,
1958; Kissinger, 1960; Osgood, 1979). Utilitarian argu-
ments for the development of tailored nuclear capabil-
ities go beyond deterrence to consider nuclear
capabilities as warfighting tools to address discrete mili-
tary challenges for which more traditional high-yield
nuclear capabilities are ill equipped. Both academics and
policymakers have suggested that nuclear weapons are
needed that reliably produce ‘special effects’ with much
lower collateral damage to destroy or otherwise neutralize
targets (Dowler, Howard & Joseph, 1991; Potter et al.,
2000; Blair, Carns & Vitto, 2004; Levi, 2004; Tertrais,
2011; Lieber & Press, 2013; Davis et al., 2019). The
2002 US Nuclear Posture Review notes three types of
targets for tailored nuclear weapons: ‘hardened or deeply
buried facilities; chemical and biological agents; and
mobile and relocatable targets’.
1
Others point to the
substantially lower levels of collateral damage associated
with the use of tailored nuclear weapons (Younger,
2000).
Scholars have also recently argued that tailored
nuclear weapons offer a useful tool for improving crisis
stability by controlling escalation (Colby, 2014; Kroenig,
2015, 2016, 2018). In work re-examining the with-
drawal of nuclear forces in Europe, for example, Kroenig
notes that the decision to ‘eliminate tactical nuclear
weapons from Europe has left Russia with a wide range
of options on the nuclear escalation ladder’ – suggesting
that the deployment of a symmetrical nuclear capability
might limit these options (Kroenig, 2015, 2016). This
1
Nuclear Posture Review Report, 8 January 2002. This report and
the relevant text is also discussed in Glaser & Fetter (2005).
Reddie & Goldblum 761
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