Alliances, signals of support, and military effort
| DOI | 10.1177/13540661211033890 |
| Published date | 01 December 2021 |
| Author | Matthew DiGiuseppe,Patrick E. Shea |
| Date | 01 December 2021 |
https://doi.org/10.1177/13540661211033890
European Journal of
International Relations
2021, Vol. 27(4) 1067 –1089
© The Author(s) 2021
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DOI: 10.1177/13540661211033890
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E
JR
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Alliances, signals of support,
and military effort
Matthew DiGiuseppe
Leiden University, Netherlands
Patrick E. Shea
University of Houston, USA
Abstract
Do alliances allow states to share defense burdens and reduce military spending?
Despite expectations that alliances should lead to decreased military spending, the
empirical record offers mixed findings. We argue that not all alliances are reliable;
thus, only allies that receive signals of reassurance will rely on the external security
of allies and subsequently reduce their military spending. Compared to states that
do not receive additional signals, these reassured allies will have greater confidence
that an ally will come to their aid. As a result, third-party aggressors are deterred
and the demand for military spending will decrease. We test this argument with an
analysis of US signals of support, alliance commitments, and military spending. We
find that American alliances without additional signals of support have a negligible
effect on military spending. Yet, we observe that alliances are negatively associated
with military spending when signals of support are present. Additional tests indicate
that alliance commitments, coupled with strong US signals, are also associated
with lower military spending in the rivals of US allies. Our results potentially help
explain the mixed evidence in the arms-versus-allies and burden-sharing literatures
and further demonstrate that extra-alliance signals play an important role in the
practice of International Relations.
Keywords
Alliances, military expenditure, security, foreign policy, burden sharing, quantitative
analysis
Corresponding author:
Matthew DiGiuseppe, Leiden University, P.O. Box 9555, Leiden, South Holland 2300 RA, Netherlands.
Email: m.r.di.giuseppe@fsw.leidenuniv.nl
1033890EJT0010.1177/13540661211033890European Journal of International RelationsDiGiuseppe and Shea
research-article2021
Article
1068 European Journal of International Relations 27(4)
In a surprise announcement in June 2018, US President Trump declared an end to joint
military exercises with South Korea in an attempt to curb North Korea’s nuclear pro-
gram (Smith and Stewart, 2018). These exercises were originally designed to increase
coordination and readiness of US and South Korean forces and act as a way to “reaf-
firm US commitment to the alliance.”1 While the military exercises were later re-
scaled, the initial announcement raised concerns about US’ commitment to South
Korea’s security. Shortly after President Trump’s decision, South Korea announced it
was going to build its own aircraft carrier and increase military spending by 10%
because of the “recent uncertain security environment" (Smith, 2019). A similar situa-
tion played out in Europe in June 2020. The Trump administration reduced the number
of troops stationed in Germany by 25% in what was interpreted as retaliation for
Germany’s “delinquent” contributions to the North Atlantic Treaty Organization
(NATO). This has led many in Europe to further question the US’ commitment to the
security pact. The action led the German defense minister, Annegret Kramp-
Karrenbauer, to remark “it means we Europeans must become able to act more so than
is the case today.”
Alliances, like NATO or the US–South Korea alliance, are designed to reduce uncer-
tainty between states and to deter adversaries. If sufficiently credible, interstate alliances
allow states to share the burden of defense and benefit from economies of scale (Altfeld,
1984; Conybeare, 1992, 1994; Lake, 1999). Subsequently, alliances can help leaders
overcome the limitations of fixed budget constraints and allow governments to dedicate
more resources toward domestic consumption without sacrificing security (Allen and
DiGiuseppe, 2012; Kimball, 2010; Narizny, 2003). Conversely, the absence of credible
alliances prompts leaders to divert money from domestic consumption to increase the
provision of security. The possibility of forming alliances thus presents a trade-off.
Governments can arm externally by allying or they can arm internally by increasing their
military spending. This trade-off implies clear observable outcomes; researchers should
observe lower military spending in states with alliances relative to those that forgo an
alliance. Further, states with lower military effort should be more likely to form alliances
(Diehl and Goertz, 2001; Morrow, 2000).
Despite these logical expectations, there is mixed evidence of substitution between
alliances and domestic armaments. Some work finds evidence that arms and alliances are
substitutes (Allen and DiGiuseppe, 2012; Conybeare, 1992, 1994; Kimball, 2010;
Morrow, 1993; Sorokin, 1994), while others find them to be complements (Diehl, 1994;
Horowitz et al., 2017; Morgan and Palmer, 2000). Why do we observe this disparity in
results? One potential answer is that not all alliances and alliance partners are equal.
While defensive pacts may hold similar commitments on paper, the strength of the com-
mitment to intervene is dependent on other factors. If allies cannot trust each other’s
commitment, they will make themselves vulnerable if they reduce their own military
expenditure. As such, the willingness of states to reduce military spending should vary
with the credibility of the alliance. The difference in the ability of allies to demonstrate
the credibility of their commitment in an anarchic system had been the focus of years of
alliance research (Leeds, 2003; Morrow, 1994; Smith, 1995). Scholars have only begun
to apply this logic to understanding the arms-versus-allies trade-off. Notably, DiGiuseppe
and Poast (2018) argue that because democratic institutions impose greater costs on
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