The central question of this dissertation is: During the course of a war, what induces states to accept the end of hostilities and sue for peace? Despite the wide variation in how wars end and the significance that variation holds to the making of post-war peace, International Relations (IR) scholars have generally neglected this key wartime behavior of states. To that end, this dissertation analyzes the factors that induce a losing belligerent to accept an end to hostilities before battlefield destruction. I argue that states will surrender or quit a war when the decision-makers experience high levels of strategic vulnerability during the course of the war. That is, it is the growing disjuncture between military means and political ends that result from the defeat of a state's military strategy rather than domestic regime type, simple military calculations or cost-related motives that lead states to concede defeat.I develop and test my arguments in two stages. First, this research develops a common conceptual framework for understanding war termination based on the notion of endgame phase of conflicts. Second, I test my argument through five in-depth case studies: the German surrender case of both World War I and World War II; the Japanese surrender case of World War II; the Egyptian surrender case in the October War; and the U.S. case of disengagement during the Vietnam War. The findings from the case studies strongly support the theoretical arguments developed in the study. Ultimately and contrary to the established literature on war termination, the factors that impact the probability of continued resistance during wars serve as the major determinant in understanding war termination.