The purpose of my paper is to trace the evolution of the concept of peacekeeping during the formation of United Nations Emergency Force, the first UN peacekeeping force, which was created in response to the 1956 Suez Crisis. I seek to examine how United Nations leaders arrived at the principles that would define peacekeeping as a viable paradigm for curtailing local conflicts. The main goal of my paper is to assess the relative importance of immediate politico-military considerations and long-term, precedential legal considerations in the establishment of the UNEF. I give a brief summary of the Suez Crisis and previous UN operations, to set my discussion in context. Then, I discuss the development of the principles that came to define peacekeeping through an analysis of the General Assembly’s First Emergency Special Session and the Secretary-General’s negotiations with the government of Egypt. In particular I seek to explain why the concept of peacekeeping transformed dramatically over the course of these negotiations, focusing on the impact of specific diplomats, the demands of competing regional blocs, and major questions of principle that continually resurfaced through the debates. I conclude with a discussion of how a precedential framework for peacekeeping grew out of an operation formed largely ad hoc.