She didn't put off the tough decisions. She spoke her convictions. And, together with Ronald Reagan, she changed the world.

Margaret Thatcher, who served three consecutive terms as Great Britain's prime minister, died Monday at the age of 87 after suffering a stroke. She was remembered in America, and in Britain, as a bulwark not only against Communism in the 1980s but against the growth of the state -- an ideology that will long outlive her on both sides of the Atlantic Ocean.

"Margaret Thatcher was a towering political figure. Very few leaders get to change not only the political landscape of their country but of the world. Margaret was such a leader. Her global impact was vast," former British Prime Minister Tony Blair said.

President Obama, in a statement, said Thatcher and Reagan reminded "the world that we are not simply carried along by the currents of history—we can shape them with moral conviction, unyielding courage and iron will."

Thatcher is remembered for her controversial, but successful, efforts to rein in government spending, privatize state entities and take on the unions. The success of her policies in Britain was arguably a force multiplier for the strength of conservatism in the United States under Reagan.

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"She was really a fearless leader who always followed core conservative principles," said Nile Gardiner, director of the Margaret Thatcher Center for Freedom at the Heritage Foundation in Washington. "The foundations of the Reagan revolution were actually laid by the Thatcher revolution in Britain."

Her speeches and her convictions can be heard echoing today, in the modern conservative arguments on tax policy, on regulation and other areas in Washington. The idea that a rising tide lifts all boats -- to conservatives, the notion that encouraging wealth creation helps the economy as a whole -- was perhaps best articulated in her last House of Commons speech in 1990.

Challenged by a member who pointed out that the gap between rich and poor grew under her stewardship, she retorted: "All levels of income are better off than they were. ... What a policy, (the member of Parliament) would rather have the poor poorer, provided the rich were less rich. That is a liberal policy."

Former Reagan economic adviser Art Laffer, summing up Thatcher's economic approach, said "she knew how to add numbers, she knew how to look at incentives."

"She knew perfectly well that if you tax people to work and pay people who don't work, you're going to get lots of people not working," he told Fox News.

Reagan biographer Craig Shirley said Thatcher has had, in America, an even more enduring influence on foreign policy. He described how Reagan and Thatcher viewed global threats as a "black and white proposition."

"The good guys had to be very strong and very careful, or else they were going to lose to the bad guys," Shirley said. He said American conservatism continues to look to both leaders for "inspiration" on that front.

Thatcher made history as the first female prime minister and the longest-serving in almost two centuries.

But those accomplishments were overshadowed by her record in office. She took on the unions and won. She sold off state-owned monopolies and tackled inflation despite the dire economic consequences it caused in the short run.

"We are rolling back the frontiers of socialism and returning power to the people," she once said.

Together with Reagan, she confronted Communism, reaching out to former Soviet leader Mikhail Gorbachev. Her alliance with Reagan was considered critical in defeating Communism, but also in strengthening the bond between Great Britain and America.

Former President George W. Bush, in a statement, called Thatcher an "inspirational leader who stood on principle and guided her nation with confidence and clarity."

"Prime Minister Thatcher is a great example of strength and character, and a great ally who strengthened the special relationship between the United Kingdom and the United States," Bush said.