More than any other prime minister since 1945, Margaret Thatcher changed the course of British history. In one sense, like any politician, she was a product of her times, but don’t let that mislead you: Only she could have done what she did.

No other U.K. politician of her time or since has had her combination of courage and single-mindedness. To meet the challenges she faced, she needed both. While she was in office, the country’s voters never much liked her, and to their shame Britain’s chattering classes despised her throughout. However, enough of the country believed she was necessary to keep her in power for 11 years. They were right -- she really was necessary.

“She did not just lead our country, she saved our country,” said Prime Minister David Cameron on Monday. “I believe she’ll go down as the greatest British peacetime prime minister.” She will, but it’s telling that the word “peacetime” jars. Thatcher saw herself, I think, as a wartime prime minister. There were enemies abroad, most notably in Argentina, and there were enemies at home who were very much more dangerous -- Britain’s trade unions. She wanted no accommodation with either kind of foe. She set out to crush them, and crush them she did.

Take No Prisoners

To understand why the British, a tolerant people inclined to moderation in most things, supported this take-no-prisoners approach to government, you must understand the depths to which the country had fallen by 1979, when Thatcher first came to power. Five years earlier, a previous Tory government had been voted out of office after it had tried, and failed, to settle a strike by the coal miners’ union. That strike had literally shut down the country. Edward Heath’s government called a general election asking, “Who governs Britain, us or the unions?” The country gave its answer by voting in a Labour government.

Characteristically, Britain’s then-militant unions showed no restraint in victory. Seeking ever-higher wages, public-sector unions called a series of strikes in the winter of 1978-79, the “Winter of Discontent,” leading to the biggest mass stoppage since the General Strike of 1926. Bodies were left unburied when gravediggers stopped work. Leicester Square became a rat-infested garbage dump, the trash piled 10 feet deep.

With voters at the point of despair, Labour Prime Minister James Callaghan returned from a meeting in (of all places) Guadeloupe to say the country was taking “rather a parochial view” of these problems. The U.K.’s best-selling tabloid newspaper, The Sun, led next day with the indelible headline, “Crisis? What Crisis?” and the government’s fate was sealed.

This is the sense in which Thatcher, who won the election in May 1979, was a product of the times. Even so, she was rare among leading conservatives for her determination to end the war she rightly believed the unions had already declared not with compromise, but with total victory. She and an inner circle of ministers made elaborate preparations (building up coal stocks, for instance, and restricting the unions’ right to strike in sympathy with other aggrieved workers) so that the government could face and win the next coal miners’ strike -- which it did. In that battle, the National Union of Mineworkers wasn’t just beaten -- it was wiped out.

Further measures to limit union rights followed. British unionism, which had staked everything on confrontation rather than cooperation, went into rapid decline. In a second front in the same war, Thatcher led an assault on the U.K.’s state-owned enterprises -- she brought the term “privatization” into common usage. She also sold the country’s publicly owned housing stock. She believed in free enterprise and thought the state had grown out of bounds, but she was no more driven by a deeply thought-through ideology than her friend Ronald Reagan. She got little respect from intellectuals and mostly returned the compliment. Her instincts were her guide.

Broken Alliance

Most consequentially of all, she broke the alliance between the Labour Party and organized labor, thus remaking the political opposition. Subsequent Labour governments made no move to restore the rights that Thatcher had taken away. They knew how unpopular that would be. Reluctantly and by degrees, the Labour Party moved to the right, until it eventually had a leader, Tony Blair, whom the Economist magazine once celebrated on its cover as “The Strangest Tory Ever Sold.”

The reconstruction of the Labour Party was Thatcher’s most significant achievement. But it’s worth remembering that her triumph over the unions would never have been consolidated if she hadn’t won another war, as well -- the one over some tiny, barely inhabited islands in the far South Atlantic. In this other pivotal moment, she showed the same unflinching determination as she had at home, together with another trait common to those whom history anoints as great leaders -- astounding luck.

The war to win back the Falklands from the Argentine force that occupied them in 1982 was, by any standards, a reckless venture. By the early 1980s, Britain lacked the capacity to dominate even a weak military opponent at that distance. Argentina was fighting close to home. It had state-of-the-art air-to-surface missiles and much faster aircraft than the U.K.’s ship-launched jets, as well. Argentina should have won the war and nearly did. It lost through a combination of pantomime incompetence and fecklessness -- things that Thatcher had no right to count on. A sensible prime minister would have argued for sanctions and a negotiated settlement. Thatcher wasn’t interested. You don’t win wars that way.

If Britain had lost the Falklands War, the humiliation would have been abject, and Thatcher’s chances of being seen as the country’s greatest “peacetime” prime minister would have been zero. There would have been no subsequent domestic achievements, either, since she would probably have failed to win re-election.

Falklands Triumph

The Falklands victory expunged memories of the Suez crisis of the 1950s and sustained Britain’s “proud island nation” myth for several more decades -- several decades too long. It helps to sustain that myth even now, though with gradually diminishing power. It shapes attitudes to Europe, and much else. (And a good thing, too, she would have said. Didn’t she warn us how Europe would make a hash of things?)

The very qualities that made Thatcher indispensable as the scourge of the U.K.’s unions and toxic public sector came closer than most Britons realize to making her a nullity through foreign misadventure. She was lucky -- as great leaders have to be. And the fact remains, she won the war that mattered most -- the war to save the British economy. For that, in my view, no praise is too great.

(Clive Crook is a Bloomberg View columnist. The opinions expressed are his own.)

To contact the writer of this article: Clive Crook at ccrook5@bloomberg.net

To contact the editor responsible for this article: James Gibney at jgibney5@bloomberg.net