Promoted to Minister of External AffairsBy the time NATO was in place, Pearson had left the civil service for politics. In September 1948, he became minister of external affairs and thereafter represented Algoma East, Ontario, in the House of Commons. As the minister, he helped lead Canada into the Korean War as a benefactor to the UN army and, in 1952, he served as president of the UN General Assembly, where he tried to find a solution to all the conflict. His efforts was disliked by the Americans, who considered him too inclined to compromise on difficult points of principle. His greatest diplomatic achievement came in 1956, when he proposed a UN peacekeeping force as a means for easing the British and French out of Egypt during the Suez Crisis. His plan was applied, and as a reward he received the Nobel Peace Prize in 1957.Leader of the Liberal PartyBy then Pearson was no longer in the office. He and the St-Laurent government were blamed amass for not standing with Britain in 1956. The Liberals were defeated, St-Laurent resigned as leader, and at a convention in January 1958 Pearson defeated Paul Martin Sr. to become the party leader. The Liberals faced a minority Conservative government under John Diefenbaker, and for his first act as the leader of the opposition, Pearson challenged Diefenbaker to resign and turn the government over to him. Diefenbaker belittled the idea and in the subsequent general election the Liberals were reduced to 49 out of the 265 seats in the Commons. Pearson began the slow task of rebuilding the party. With the assistance of some parliamentary debaters such as Paul Martin and J.W. Pickersgill, along with party workers such as Walter Gordon, Mitchell Sharp and Maurice Lamontagne. He then re-established the Liberals as a national party and In the 1962 general election, Pearson raised the party’s total number to 100 seats. In 1963, the Diefenbaker government collapsed because of the issue of nuclear weapons and thus in the subsequent election the Liberals won 128 seats to form a minority government.Prime Minister from 1963 to 1968Pearson took office on 22 April 1963. His government was expected to be more businesslike than Diefenbaker’s but instead proved to be clumsy, effectively aborting its first budget. Much of the Parliament’s time was spent in bitter prejudice and personal wrangling, culminating in the never-ending flag debate of 1964. In 1965, Pearson called a general election but again failed to secure a majority. In the next year, the Munsinger scandal erupted with even more prejudice bitterness.The year 1965 marked a dividing line in his administration, as Finance Minister Walter Gordon departed, and Jean Marchand and Pierre Trudeau from Québec became well-known in the Cabinet. Pearson’s attempts in his first term to appease Québec and the other provinces with “co-operative federalism” and “bilingualism and biculturalism” were replaced in his second term by a firm federal response to provincial demands and by the Québec government’s attempts to seize federal roles in international relations. During his centennial visit, French president Charles de Gaulle spoke the separatist slogan “Vive le Québec libre” to a crowd in Montréal, Pearson issued an official reprimand and de Gaulle promptly went home. In December 1967, Pearson announced his intention to retire and in April 1968 a Liberal convention picked Pierre Trudeau as his successor.Pearson’s LegacyFor all its external chaos, the Pearson government left behind a remarkable legacy of legislation: a Canada Pension Plan, a universal medicare system, a unified armed force, and also a new flag. Nonetheless, its approach to the problem of Canada’s economically disadvantaged regions was less successful and its legacy, which included the Glace Bay heavy-water plant, was decidedly mixed. Not all of these initiatives proved productive and some were costly, but they represented the high points of the Canadian welfare state that generations of social thinkers had dreamed about. During retirement, Pearson worked on his memoirs and on a study of international help for the World Bank.