In this chapter, students will learn about the concepts, evolution and political debates concerning peace operations. Peace operations range from small observation and monitoring missions to large peacebuilding initiatives in war-torn societies. Some commentators argue that it includes combat but falls short of outright belligerency, known as peace enforcement or ‘robust peacekeeping’. A shift in the concepts, and discourse about, peace operations has occurred since the mid-1990s. Together with UN reforms, the shift is represented as an international response to the needs of human security, notably civilian protection and enlightened governance through liberal peacebuilding inter ventions. However, peace operations also reflect power distributions in the international system and, as a form of crisis management, serve to sustain rather than transform the global system. Reforms and revisionist debates have shifted UN peace operations into protection of civilians by force if necessary and into partnerships with regional military formations.