Military power is arguably the most significant factor in the study of international politics. Yet raw measures of military strength do not always explain how well states fight or how wars unfold. For instance, the United States easily defeated the Iraqi military in 1991, despite many predictions that the conflict would take a heavy toll, while Washington has suffered far greater costs at the hands of much weaker opponents on numerous occasions. The purpose of this course, therefore, is to examine why states (and non-state actors) succeed or fail in harnessing their resources, devising novel tactics, developing new weapons, motivating their troops, and, in the end, winning the wars they fight. Specifically, the course will address this question by surveying theories that seek to explain how factors such as geography, strategy, technology, domestic institutions, and culture can impact battlefield performance. In addition, it will place these arguments in historical context and assess their relevance for contemporary policy debates.