Teams are the foundational building blocks of the military, which uses a hierarchical structure built on and around teams to form larger units. Consequently, team effectiveness has been a substantial focus of research within the military for decades to ensure military teams have the human capabilities to complete their missions and address future challenges successfully. This research has contributed greatly to broader team theory and informed the development of evidence-based interventions. Team-focused research supported or executed by the military has yielded major insights into the nature of team performance, advanced the methods for measuring and improving team performance, and broken new ground in understanding the assembly of effective teams. Furthermore, military research has made major contributions to advancing methodological and statistical techniques for studying teams. We highlight the military contributions to the broader team literature and conclude with a discussion of critical areas of future research on teams and enduring challenges for both the military and team science as a whole.