The participation of military personnel in health-related activities remains highly controversial. Drawing on four case studies that extend from peacetime to post-conflict situations, this chapter analyses where, and under what circumstances, military actors have previously engaged in providing health assistance. It also examines the controversies, criticisms, and perceived benefits that have accompanied that activity. The chapter advances an analytical framework for understanding the types of situations in which military actors have been called upon to assist, and what these signal for future health crises.