Alliances, signals of support, and military effort

Do alliances allow states to share defense burdens and reduce military spending? Despite expectations that should lead decreased spending, the empirical record offers mixed findings. We argue not all are reliable; thus, only allies receive signals of reassurance will rely on external security subsequently their spending. Compared do additional signals, these reassured have greater confidence an ally come aid. As a result, third-party aggressors deterred demand for spending decrease. test this argument with analysis US support, alliance commitments, find American without support negligible effect Yet, we observe negatively associated when present. Additional tests indicate coupled strong also lower in rivals allies. Our results potentially help explain evidence arms-versus-allies burden-sharing literatures further demonstrate extra-alliance play important role practice International Relations.