International alliance is an agreement between state actors to combine military and economic resources in order to pursue common objectives against a shared adversary. Alliances are a key feature of the contemporary global system, and they have served as critical tools for addressing an array of strategic challenges, from regional security issues in Europe to great-power competition in Asia.
However, assessing the quality of an ally’s commitment requires more than simply measuring its responses in wartime crises. A more accurate measure is to examine how a state’s commitments converge and diverge over time, which allows scholars to better understand the dynamic nature of alliance interdependence.
This article draws on a number of recent developments to develop an empirical framework for measuring the reliability of national allies. In doing so, it sheds light on why some states’ investments in multilateral alliances pay off while others do not.
The resulting framework captures the dynamics of alliances in a much more realistic way than previous efforts. In contrast to some skeptics, my approach does not imply that states need to agree on every issue in order to be reliable. Rather, allies can be reliably cooperative in one area of policy when their interests converge but unreliable in another when they do not.
This approach is also more relevant to real-world decisionmaking, as it allows the United States to better understand its allies’ reactions to its actions during a crisis. This might be difficult, particularly if the United States expects unqualified support during a crisis, but it may help the United States avoid undesirable reactions such as dealignment or bandwagoning.
About the Author
