Defense date: 20/09/2010Examining Board: Lene Hansen (Univ. Copenhagen), Friedrich V. Kratochwil (EUI) (Supervisor), Ramesh Thakur (Univ. Waterloo, Canada), Pascal Vennesson (EUI/RSCAS)This thesis is motivated by the puzzle that while the practice of collective security continues to grow and expand with more and bigger peacekeeping operations, the system is struggling increasingly to address the threats and stabilize the global world. Thus to find out more about the justificatory background of the reinvention of collective security after the end of the Cold War, an in-depth critical analysis is conducted of the UN Protection Force (UNPROFOR) for the former Yugoslavia and the subsequent peacebuilding missions. Question are asked abou...