Uncertainty surrounding US alliance commitments has led to concern that America’s allies are now more likely to be targeted militarily. Such shifts in the commitment of a great power to a smaller security partner are nothing new, however, and the historical record suggests their consequences are varied. In some cases, partner states are the target of aggression, but in others, they actually reach new settlements with their adversaries to reduce security threats. My dissertation identifies the conditions under which a diminished great power security commitment causes conflict versus negotiations between partner states and adversaries. With this project, I hope to improve both practitioners’ and scholars’ understanding of the consequences of changing international security partnerships and great power restraint.