In 1975, Margaret 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, ledby President Ronald Reagan. She led Britain to victory in the 1982 war with Argentina over the Falklands Islands. Continuously, Thatcher won elections as Prime Minister from 1979-1990. Next to Winston Churchill many consider Thatcher to be the most important British political leader of the twentieth century.