From the abstract:
Multifunctional peace operations have become an integral part of international society to the extent that they are now one of the major regulating institutions of international relations. The United Nations (UN) is the main player in setting up such operations. The UN has seen a major but gradual evolution of its role in maintaining and establishing peace. Having developed peacekeeping as a form of impartial interposition between belligerents during the Suez Crisis in 1956, the UN has continually broadened its sphere of action. These cumbersome and complex operations are demanding and present the UN with a number of challenges.