Scholars and military practitioners alike have long sought to understand why some country's militaries fight hard when facing defeat while others collapse. In Endurance and War, Jasen Castillo presents a new unifying theory-cohesion theory-to explain why national militaries differ in their staying power. His argument builds on insights from the literatures on group solidarity in general and military effectiveness in particular, which argue that the stronger the ties binding together individuals in a group of any kind, the higher the degree of cohesion that a group will exhibit when...