External threat and alliance formation

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23 Scopus citations


Scholars generally believe that external threats drive military alliances. However, existing statistical studies of alliance formation fail to find a consistent relationship between the two. In this research note, I argue that this is because they do not correctly proxy for the existence of an external threat. Previous studies employ measures based on past militarized disputes, but a valid measure must capture expectations of future militarized disputes. To identify a better indicator of external threat, I situate alliance formation in crisis bargaining theory. The framework suggests that a target will be more likely to seek an alliance as its challenger's probability of winning in war increases. I test this hypothesis and find a positive relationship between external threat and alliance formation. My analysis provides support for a central pillar of alliance theorizing. Additionally, it suggests that any pacifying effects of alliances may be difficult to uncover, as alliances form when the probability of conflict is already high.

Original languageEnglish
Article numbersqw054
Pages (from-to)736-745
Number of pages10
JournalInternational Studies Quarterly
Issue number3
StatePublished - Sep 1 2017

Bibliographical note

Publisher Copyright:
© The Author (2017). Published by Oxford University Press on behalf of the International Studies Association. All rights reserved.

ASJC Scopus subject areas

  • Sociology and Political Science
  • Political Science and International Relations


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