In 1956 Diefenbaker was elected party leader and became prime minister in 1957 when the Progressive Conservatives were elected to a minority government. The party became the majority after the 1958 elections. As prime minister, Diefenbaker had a stormy relationship with U.S. President John F. Kennedy and refused to blindly follow America's lead in foreign policy. After the 1959 Cuban communist revolution, Diefenbaker refused to end trade with Cuba, withheld Canada's membership in the Organization of American States (OAS), and supported a nuclear test–ban treaty in Europe.
Tensions between Kennedy and Diefenbaker were further exacerbated during the 1962 Cuban Missile Crisis. Kennedy took action without notifying Diefenbaker and then requested that Canada participate in the American blockade of Cuba. Angry at not being consulted, the prime minister refused to put the Canadian armed forces on a state of heightened readiness.
The Progressive Conservatives lost to the Liberals under Lester B. Pearson's leadership in 1963, and thus Diefenbaker stepped down as prime minister. He remained party leader until being defeated at a party convention in 1969. Diefenbaker's constituency continued to return him to Parliament, however, until he died of heart failure on 16 August 1979 in Ottawa, Ontario.
John David Rausch Jr.
Robinson, Basil H. Diefenbaker's World: A Populist in Foreign Affairs. Toronto: University of Toronto Press, 1989.; Smith, Denis. Rogue Tory: Life and Legend of John G. Diefenbaker. Toronto: Macfarlane Walter and Ross, 1995.