Margaret Thatcher, the “Iron Lady” of British politics, who pulled her country back from 35 years of socialism, led it to victory in the Falklands war and helped guide the United States and the Soviet Union through the Cold War’s difficult last years, died Monday. She was 87.

“It is with great sadness that Mark and Carol Thatcher announced that their mother, Baroness Thatcher, died peacefully following a stroke this morning,” a statement from her spokesman, Lord Tim Bell, said. She had been in poor health for months, and suffered from dementia.

Mrs. Thatcher was the first woman to become prime minister of Britain and the first to lead a major Western power in modern times. Hard-driving and hard-headed, she led her Conservative Party to three straight election victories and held office for 11/ years — May 1979 to November 1990 — longer than any other British politician in the 20th century.

Queen Elizabeth II and Prime Minister David Cameron offered tributes to what Mr. Cameron called “a great leader, a great prime minister, a great Briton.”

Buckingham Palace said the Queen was “sad to hear the news” and would be sending a private message of sympathy to the family.

A statement from the White House said that “the world has lost one of the great champions of freedom and liberty, and America has lost a true friend.”

The tough economic medicine Mrs. Thatcher administered to a country sickened by inflation, budget deficits and industrial unrest brought her wide swings in popularity, culminating with a revolt among her own cabinet ministers in her final year and her shout of “No! No! No!” in the House of Commons to any further integration with Europe.

Thatcherism

But by the time she left office, the principles known as Thatcherism — the belief that economic freedom and individual liberty are interdependent, that personal responsibility and hard work are the only ways to national prosperity, and that the free-market democracies must stand firm against aggression — had won many disciples. Even some of her strongest critics accorded her a grudging respect.

At home, Mrs. Thatcher’s political successes were decisive. She broke the power of the labour unions and forced the Labour Party to abandon its commitment to nationalised industry, redefine the role of the welfare state and accept the importance of the free market.

Abroad, she won new esteem for a country that had been in decline since its costly victory in World War II. After leaving office, she was honoured as Baroness Thatcher of Kesteven. But during her first years in power, even many Tories feared that her election might prove a terrible mistake.

In October 1980, 17 months into her first term, Mrs. Thatcher faced disaster. More businesses were failing and more people were out of work than at any time since the Great Depression. Racial and class tensions smouldered so ominously that even close advisers worried that her push to staunch inflation, sell off nationalised industry and deregulate the economy was devastating the poor, undermining the middle class and courting chaos.

At the Conservative Party conference that month, the moderates grumbled that they were being led by a free-market ideologue oblivious to life on the street and the exigencies of realpolitik. With electoral defeat staring them in the face, cabinet members warned, now was surely a time for compromise.

To Mrs. Thatcher, they could not be more wrong. “I am not a consensus politician,” she had often declared. “I am a conviction politician.”

In an address to the party, she played on the title of Christopher Fry’s popular play “The Lady’s Not for Burning” in insisting that she would press forward with her policies. “Turn if you like,” she told the faltering assembly. “The lady’s not for turning.” Her tough stance did the trick. A party revolt was thwarted, the Tories hunkered down, and Mrs. Thatcher went on to achieve great victories. She turned the Conservatives, long associated with the status quo, into the party of reform. Her policies revitalised British business, spurred industrial growth and swelled the middle class.

But her third term was riddled with setbacks. Dissension over monetary policy, taxes and Britain’s place in the European Community caused her government to give up hard-won gains against inflation and unemployment. By the time she was ousted in another Tory revolt — this time over her resistance to expanding Britain’s role in a European Union — the economy was in a recession and her reputation tarnished.

To her enemies she was — as Denis Healey, chancellor of the Exchequer in Harold Wilson’s government, called her — “La Pasionaria of Privilege,” a woman who railed against the evils of poverty but who was callous and unsympathetic to the plight of the have-nots. Her policies, her opponents said, were cruel and short-sighted, widened the gap between rich and poor and worsened the plight of the poorest.

Relations with Russia

Her relentless hostility to the Soviet Union and her persistent call to modernise Britain’s nuclear forces fed fears of nuclear war and even worried moderates in her own party. It also caught the Kremlin’s attention. After a hard-line speech in 1976, the official Soviet news agency Tass gave her a sobriquet of which she was proud: the Iron Lady.

Yet when she saw an opening, she proved willing to bend. She was one of the first Western leaders to recognise that the Soviets would soon be led by a member of a new generation, Mikhail S. Gorbachev, and invited him to Britain in December 1984, three months before he came to power. “I like Mr. Gorbachev,” she declared. “We can do business together.”

Her rapport with the new Soviet leader and her friendship with President Ronald Reagan made her a vital link between the White House and the Kremlin in their tense negotiations to halt the arms race of the 1980s.

Brisk and argumentative, she was rarely willing to concede a point and loath to compromise. Colleagues who disagreed with her were often deluged in a sea of facts, or what many referred to as being “handbagged.”

“She had high standards, and she expected everyone to do their work,” John O’Sullivan, a special adviser to the prime minister, recalled in 1999. “But there was a distinction. She was tougher on her ministers than she was on her personal staff. The more humble the position, the nicer she was.”

Despite her being the first woman to lead a major political party in the West, she rubbed many feminists the wrong way. “The battle for women’s rights has largely been won,” she declared. “I hate those strident tones we hear from some women’s libbers.”

She relished being impolitic. “You don’t follow the crowd,” she often said. “You make up your own mind.”

Britain’s arts and academic establishments loathed her for cutting their financing and considered her tastes provincial, her values narrow-minded. In 1985, two years into her second term, she was proposed for an honorary doctorate at Oxford, a laurel traditionally offered Prime Ministers who had attended the university, as she had. The proposal, after debate among the faculty, was rejected.

Yet her popularity remained high.

“Margaret Thatcher evoked extreme feelings,” wrote Ronald Millar, a playwright and speech writer for the Prime Minister. “To some she could do no right, to others no wrong. Indifference was not an option. She could stir almost physical hostility in normally rational people, while she inspired deathless devotion in others.” — New York Times News Service

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