Urquhart's professional life has been in many respects, a history of the U.N. In 1945 after serving in the British Army, he was recruited in London to serve as the personal assistant to the first secretary-general, Trygve Lie. From 1954 to 1971 he served in various capacities under American undersecretary Ralph Bunche. He was involved in the Congo crisis in the early 1960s, and peacekeeping in Cyprus, Kashmir and the Middle East. After 1972, Urquhart was one of the principal political advisors of the secretary general, and served as the under-secretary general for special political affairs, working on Lebanon, Israel and Palestine and Namibia among others. He retired from the U.N. secretariat in 1986.
The author of several books, Urquhart's last major work was the biography, Ralph Bunche: An American Life. He wrote the book, he said, because though Bunche was one of the most important people of the last century, society has totally forgotten him. Bunche was the first African-American to be an official in the State Department and was the most senior U.N.
official. Urquhart has said of him, "He was quite remarkable. He invented peacekeeping, he wrote two chapters of the United Nations Charter, he won the Noble Peace Prize and he also wrote a great deal of the basic literature in the 1930s of the Civil Rights movement. He was a
remarkable, absolutely extraordinary man."
The Ralph E. and Doris M. Hansmann Lecture Series was established in 1993 to honor Hansmann, Class of 1940, and his wife. The series supports annual lectures in the field of public policy.