This chapter traces the development of the 1949 Geneva Conventions from their origins in pre-1949 treaty law through the 1977 Additional Protocols and to the present. It argues that international humanitarian law (IHL) has historically emerged from a contentious mix of military interest, moral values, and emotions grounded in the traumatic episodes leading to its revision. It focuses specifically on the evolution of three general areas of IHL: the protection of combatants and prisoners of war (POWs) and captured fighters, the protection of noncombatants (or civilians), and the mechanisms for implementation and enforcement of the law. The chapter draws on novel archival research as well as key primary and secondary sources.