Uploaded March 2026 | Updated September 2026, 5 hours ago
Speaker: Rachel Metz
This project presents the concept of wartime access—decisions by states to let other states fight wars from inside their borders—and establishes its centrality to U.S. power projection. Although permissive wartime access has been a defining feature of the post-1945 world, states do not always let the United States military in. States sometimes restrict access sharply or deny it altogether. This project asks, why do states sometimes grant, sometimes restrict, and sometimes deny wartime access? It argues that the general trend of permission is attributable to states’ expectations that they will derive security benefits from the United States in exchange for granting access, and that the United States will protect them from retaliation by the target and help them manage any spillover from the war. While security factors tend to point states towards granting access, states tend to deny or heavily restrict access when the domestic political costs of open alignment with the United States are prohibitively high. The study develops a new dataset of 85 partner access decisions across eleven U.S.-led wars since 1945 and conducts paired comparisons of wartime access decisions within each war. The project concludes with a discussion of policy implications, with particular attention to wartime access in the context of a hypothetical U.S. effort to defend Taiwan.
Speaker: Rachel Metz
This project presents the concept of wartime access—decisions by states to let other states fight wars from inside their borders—and establishes its centrality to U.S. power projection. Although permissive wartime access has been a defining feature of the post-1945 world, states do not always let the United States military in. States sometimes restrict access sharply or deny it altogether. This project asks, why do states sometimes grant, sometimes restrict, and sometimes deny wartime access? It argues that the general trend of permission is attributable to states’ expectations that they will derive security benefits from the United States in exchange for granting access, and that the United States will protect them from retaliation by the target and help them manage any spillover from the war. While security factors tend to point states towards granting access, states tend to deny or heavily restrict access when the domestic political costs of open alignment with the United States are prohibitively high. The study develops a new dataset of 85 partner access decisions across eleven U.S.-led wars since 1945 and conducts paired comparisons of wartime access decisions within each war. The project concludes with a discussion of policy implications, with particular attention to wartime access in the context of a hypothetical U.S. effort to defend Taiwan.
