Thatcher, Margaret Hilda Roberts Thatcher, Baroness - 1925–, British political leader. Great Britain's first woman prime minister, Thatcher served longer than any other British prime minister in the 20th cent. In office she initiated what became known as the "Thatcher Revolution," a series of social and economic changes that dismantled many aspects of Britain's postwar welfare state.

Thatcher studied chemistry at Oxford and later became a lawyer. Elected to Parliament as a Conservative in 1959, she held junior ministerial posts (1961–64) before serving (1970–74) as secretary of state for education and science in Edward Heath's cabinet. After two defeats in general elections, the Conservative party elected her its first woman leader in 1975.

After leading the Conservatives to an electoral victory in 1979, Thatcher became prime minister. She had pledged to reduce the influence of the trade unions and combat inflation, and her economic policy rested on the introduction of broad changes along free-market lines. She attacked inflation by controlling the money supply and sharply reduced government spending and taxes for higher-income individuals. Although unemployment continued to rise to postwar highs, the declining economic output was reversed. In 1982, when Argentina invaded the Falkland Islands, a British colony, Britain's successful prosecution of the subsequent war contributed to the Conservatives' win at the polls in 1983.

Thatcher's second government privatized national industries and utilities, including British Gas and British Telecommunications. Her antiunion policies forced coal miners to return to work after a year on strike. In foreign affairs, Thatcher was a close ally of President Ronald Reagan and shared his antipathy to Communism. She allowed the United States to station (1980) nuclear cruise missiles in Britain and to use its air bases to bomb Libya in 1986. She forged (1985) a historic accord with Ireland, giving it a consulting role in governing Northern Ireland.

In 1987 Thatcher led the Conservatives to a third consecutive electoral victory, although with a reduced majority. She proposed free-market changes to the national health and education systems and introduced a controversial per capita "poll tax" to pay for local government, which fueled criticisms that she had no compassion for the poor. Her refusal to support a common European currency and integrated economic policies led to the resignation of her treasury minister in 1989 and her deputy prime minister in 1990.

Disputes over the poll tax, which took effect in 1990, and over European integration led to a leadership challenge (1990) from within her party. She resigned as prime minister, and John Major emerged as her successor. In 1992 Thatcher retired from the House of Commons and was created Baroness Thatcher. In the mid-1990s Thatcher was publicly critical of Major's more moderate policies, and she has continued to criticize publicly Conservative and Labour positions she disagrees with.

See her memoirs, The Downing Street Years (1993) and The Path to Power (1995), and her collected speeches in The Revival of Britain, compiled by A. Cooke (1989); studies by R. Lewis (1984), P. Jenkins (1987), and H. Young (1989).

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