In July 1941 President Franklin D. Roosevelt created the Office of the Coordinator of Information (later the Office of Strategic Services), a new civilian office attached to the White House, to both gather and disseminate information in connection with preparations for what looked like an inevitable war. In September 1941 Ralph Bunche was hired as an expert on Africa. Bunche also advised on general issues related to blacks in the military.
In 1944 he joined the U.S. State Department’s postwar planning unit and participated in the planning for the conference at Dumbarton Oaks to discuss a world organization. In April 1945 U.S. Secretary of State Edward R. Stettinius appointed him to the U.S. delegation to the San Francisco conference in 1945 at which the United Nations charter was drafted, to the U.N. Preparatory Commission in London later that year, and to the first session of the U.N. General Assembly held in London in 1946.
While the United States was struggling to reconcile internal conflicts regarding its public stance on the oversight of colonies and territories, Bunche showed his diplomatic dexterity at the London session by working through the Chinese delegation to introduce a resolution establishing an ad-hoc committee on information from non-self-governing territories. This committee, which later became permament, ensured international oversight of colonial administration and non-self-governing peoples.
In April 1946 Bunche was loaned to the U.N. as acting director of the Trusteeship Division for an initial period of six weeks. The loan was extended again and again at the request of the assistant secretary-general for trusteeship until the secretary-general asked the U.S. government to release him to assume the position of director of the Trusteeship Division. In a February 1947 letter to his former Harvard housemate William Hastie, Bunche still saw the U.N. as a temporary stop: "I do not look upon it as a long-enduring proposition, as I am increasingly intent on getting back to the academic fold."