In 1946, Pearson became deputy minister of external affairs. In this position, he played a leading role in the creation of the North Atlantic Treaty Organization (NATO). He entered the political arena in 1948, was elected to the Canadian Parliament, and became secretary of state for external affairs in September 1948, serving in that post until June 1957 when the Liberal Party lost its majority. Pearson served as president of the United Nations (UN) General Assembly in 1952. In this position, he tried unsuccessfully to resolve the Korean War. In 1957 he was awarded the Nobel Peace Prize for his role in mediating an end to the 1956 Suez Crisis by sending UN peacekeeping forces to the region.
In January 1958, Pearson was elected leader of the Liberal Party following the retirement of Louis Stephen St. Laurent. From 1958, Pearson clashed with Progressive Conservative Prime Minister John G. Diefenbaker. Pearson became prime minister in April 1963 following the Canadian national elections and held that post until his retirement in April 1968, when he was replaced by Pierre Trudeau. The Liberal Party never enjoyed a majority during Pearson's tenure as prime minister.
Pearson resisted U.S. efforts to involve Canada in the Vietnam War. In a 1965 speech at Temple University, he suggested that a break in the American bombing of the Democratic Republic of Vietnam (DRV, North Vietnam) might lead to negotiations. Meeting with President Lyndon B. Johnson following the speech, aides were shocked to observe Pearson being grabbed by the lapels by a frustrated Johnson.
Upon retirement, Pearson taught at Carleton University in Ottawa and worked on his memoirs. He died in Ottawa on 27 December 1972.
John David Rausch Jr.
English, John. Shadow of Heaven: The Life of Lester Pearson. Toronto: Lester and Orpen Dennys, 1989.; English, John. The Worldly Years: The Life of Lester Pearson. New York: Knopf Canada, 1992.; Hillmer, Norman, ed. Pearson: The Unlikely Gladiator. Montreal: McGill-Queen's University Press, 1999.