Bunche served on the US delegation to both the Washington Conversations on International Peace and Security Organization in 1944 and United Nations Conference on International Organization in San Francisco in 1945 that drafted the UN charter. Bunche served on the American delegation to the first session of the United Nations General Assembly in 1946. He then joined the UN as head of the Trusteeship Department, and began a long series of troubleshooting roles. In 1948 he became an acting mediator for the Middle East, negotiating an armistice between Egypt and Israel. For this success he was awarded the Nobel Peace Prize in 1950. He continued to serve at the United Nations, working on crises in the Sinai (1956), the Congo (1960), Yemen (1963), Cyprus (1964) and Bahrain in 1970, reporting directly to the UN secretary general. He also chaired study groups dealing with water resources in the Middle East. In 1957 he was promoted to Undersecretary for special political affairs, having prime responsibility for peacekeeping roles. In 1965 he supervised the cease-fire following the war between India and Pakistan. He retired from the UN in 1971.