What explains the variation in the military postures adopted by non-nuclear U.S. allies under the U.S. security guarantee and nuclear umbrella? In what ways can allies bolster deterrence? I develop Allied Integration Theory, a new framework for understanding how allies shape their capabilities, doctrine, and integration with U.S. military forces, including its nuclear weapons. Specifically, I focus on the agency exercised by allies to influence the escalation dynamics in their regional security environments.

To test Allied Integration Theory, I conduct two pairs of comparative case studies: South Korea and Japan in the post-Cold War era, and Norway and West Germany during the latter half of the Cold War. 

The analysis draws on qualitative data gathered through extensive fieldwork, including Korean- and Japanese-language primary and secondary sources—especially speech evidence and writings by key policy actors—as well as semi-structured interviews with senior policymakers and experts in both the allied countries and the United States, many of whom directly participated in intra-alliance negotiations and consultations.