This course focuses on the theory and practice of peace operations,as collective humanitarian interventions performed by the UN and regional arrangements. It touches on the balance between intervention, human rights and sovereignty, and shifts in this relationship. It situates PKOs within the notion and practice of collective security, as well as the broader agenda of international security, including North-South relations. It covers in detail the legal underpinnings of PKOs in the UN Charter, as well as the practical mechanics of setting up and running missions within DPKO. It works through successive generations of operations focusing on issues such as the use of force, the security-development nexus in peace building, and critiques of the Western liberal peace paradigm. It provides extensive examples both historical and current.