sentences:  The DPO traces its roots to 1948 with the creation of the United Nations Military Observer Group for India and Pakistan (UNMOGIP) and the United Nations Truce Supervision Organisation (UNTSO).Up to the late 1980s, peacekeeping missions were operated by six officials in the United Nations Office of Special Political Affairs, which was headed first by Under-Secretary-General Ralph Bunche, and subsequently Brian Urquhart and Marrack Goulding.From the beginning, peacekeeping operations operated with a clear doctrine that applied to its traditional or classical peacekeeping operations for inter-state ceasefires