In 1975, Margaret Thatcher (Margaret Hilda Roberts Thatcher) became a leader of the Conservatives in Great Britain. She was opposed to socialism and ran on this issue. In 1979, she was elected as Prime Minister and the Conservatives swept into power. She sold many of the nationalized industries back to private investors and made tax cuts. Thatcher stood up against the powerful labor unions and stifled the British coal and newspaper industries and broke their power. Because of her strong standards and her leadership style, she became known as the "Iron Lady." Also, Thatcher supported the United States' actions against the Communists, led by President Ronald Reagan. She led Britain to victory in the 1982 war with Argentina over the Falklands Islands. Continuously, Thatcher won three elections as Prime Minister from 1979-1987. Following a series of major demonstrations against her, stemming mainly from disquiet over the unpopular poll tax, the Conservative party voted to expel her from office in 1990. She was succeeded by John Major as Prime Minister (1990-97).
Next to Winston Churchill many consider Thatcher to be the most important British political leader of the twentieth century. In a paper done by the University of Leeds Professor Kevin Theakston & Mark Gill, Thatcher ranked in most surveys in the top 5, #4 in the 2004 MORI / University of Leeds rankings. Roy Jenkins, saying it was too early to be able to rank Tony Blair, the same could almost be said for Thatcher, though he went on to rank hers as a 'major premiership' on the grounds of her length of office, 'forthrightness of style', and as the first and (so far) only woman to hold the post. Peter Hennenssy, while sceptical about the possibilities of assessing prime ministerial performance, Hennenssy did develop what he called a 'crude taxonomy' of post-1945 prime ministers, which was 'an index of performance' or a 'premiership league'. The 'very top flight' postwar World War II prime ministers were Clement Attlee and Thatcher, in his view (Churchill would have been in this category if his two premierships were treated in combination and account taken of his wartime achievements). These were the 'two great "weathermakers" of the postwar years', he judged, setting the political agenda and transforming British politics, though he muddied the waters by implying that Thatcher could be ranked highest as she 'forged her new consensus' while Attlee 'refined his' as 'the beneficiary of a new weather system' created during the second world war. Described as 'below' those top two was the category of 'nation- or system-shifters', prime ministers who were 'remaker[s] of the country in a significant, substantial and almost certainly irreversible fashion'. Heath was in this category because of British entry to Europe and Blair because of his government's because of his government's constitutional reforms.