Progressive Conservative John Diefenbaker (1957–1963) tried to improve relations with Britain even as it was trying to enter the European Common Market, which would greatly weaken its historic ties with Canada. US President Dwight Eisenhower took pains to foster good relations with Diefenbaker. That led to approval of plans to join the United States in what became known as NORAD, an integrated air defence system, in mid-1957. Relations with President John Kennedy were much less cordial. Diefenbaker opposed apartheid in the South Africa and helped force it out of the Commonwealth of Nations. His indecision on whether to accept Bomarc nuclear missiles from the United States led to his government's downfall.