On March 24, 1999, NATO initiated the second major offensive military- campaign in its fifty-year history. Operation Allied Force was initially designed to last only a few days, long enough to convince Slobodan Milosevic to stop the ethnic cleansing in Kosovo and to pull his forces out of the disputed province. Instead of immediately complying with NATO's demands, Milosevic chose to escalate the violence against the Kosovar Albanians, perhaps hoping that the Alliance's consensus for action would shatter after a few days of bombing. The allies did disagree about many aspects of the operation, ranging from target selection to altitude restrictions and the possible use of ground troops. Despite these disagreements, the allies agreed that NATO's credibility was at stake and that they could not let Milosevic continue his escalated campaign of violence. NATO therefore found itself drawn into a major operation that lasted 78 days and involved more than 38,000 sorties. Alter Operation Allied Force ended, individual allies strove to identify the lessons learned in Kosovo and to understand the implications for future operations. The operation highlighted a number of issues for the allies to address, such as using force to achieve humanitarian goals and how to improve military capabilities in a fiscally con- strained environment.