This chapter examines the dramatic transformation of international priorities governing the purpose and principal uses of military force over the past 25 years. It distinguishes the broader historical background of armed humanitarian intervention (AHI) prior to 1989 from two subsequent, distinctive phases: a second wave of humanitarian crises and responses during the 1990s, and a more recent third wave of ethical analysis, dominated by proposals for new political arrangements that would govern collective decision-making by the international community when faced with the question of whether to deploy their military forces for the prevention or cessation of humanitarian crises. The manner in which the history of AHI is narrated is strongly dependent upon the perspectives from which AHI efforts themselves were experienced. All of the military interventions proposed or carried out for humanitarian purposes in the 1990s, however noble their intent violated every single provision of that Weinberger-Powell doctrine.