When dawn broke over London on Sept. 15, 1940, this was the geopolitical situation: The northern tier of Eurasia, from Iberia in the West to Tokyo in the East, was dominated by Nazi Germany, fascist Italy, Imperial Japan and the Soviet Union, the latter of which was observing a nonaggression pact with Berlin.

Totalitarians thus held sway over about a third of the world’s 2.3 billion people, plus a similar percentage of global economic output. In the United States, meanwhile, the incumbent president, Franklin D. Roosevelt, was running for a third term on a promise to keep out of foreign wars.

At this pivotal moment, Adolf Hitler sent a wave of military planes across the English Channel, seeking decisive victory in what was then a two-month-old air war against the last major power actively resisting him: Britain.

Royal Air Force fighters took off to confront the Luftwaffe and, during a ferocious hour of aerial combat, downed 56 of the German planes; the RAF lost only 40.

These events exactly 80 years ago proved Hitler could not establish air supremacy over the British Isles and, therefore, that he would have to scrap his plans to invade them from occupied France.

The rest, as they say, is history. It is sobering to consider how different today’s world might be if RAF pilots, who were not only Brits but also Polish exiles, Canadians and a handful of American volunteers, had not prevailed — and Germany had conquered the British Empire.

Surely the most ironic legacy of victory in the Battle of Britain is that today’s generations are free to examine, and condemn, the dark side of the leader who insisted on fighting it: Prime Minister Winston Churchill.

Lionized in the postwar decades for his refusal to deal with Hitler, and for galvanizing his country with ringing rhetoric (“never surrender”), Churchill now stands accused of imperial crimes, from advocating the use of chemical weapons in the Middle East just after World War I to countenancing mass starvation in Bengal during World War II.

His reference, in 1937, to White settlers of North America and Australia as “a higher-grade race” than the Indigenous people they displaced is one of several comments that have prompted protesters — the latest just a few days ago — to paint “racist” on his statue in London’s Parliament Square. British authorities may have to reinstall the covering with which they protected the sculpture from vandalism during protests earlier this year.

The critics have a point, even if they sometimes exaggerate: Churchill’s recommendation that Britain use toxic gas to spread “lively terror” among Kurdish and Afghan rebels probably referred to nonlethal tear gas (unlike, say, the Zyklon B that Churchill’s German enemies used at Auschwitz). The multiple causes of the Bengal famine include not only Churchill’s failure (or refusal) to supply aid, while fighting a global war, but also disruptions due to Japan’s occupation of neighboring Burma.

There’s no denying, though, that the British Empire committed many atrocities and that Winston Churchill, soldier and statesman, shares responsibility for them.

The important question is: Therefore, what? Should we teach our children that Churchill’s sins cancel out his achievements? Does he have “as much blood on his hands as some of the worst genocidal dictators of the 20th century,” as Indian writer-politician Shashi Tharoor has said? Or would a more differentiated assessment assign him credit for innocent blood that, perhaps, wasn’t spilled — by Hitler — due to British resistance?

There’s an instructive parallel in the historical revisionism now being visited upon a very different figure: Mohandas Gandhi, leader of the nonviolent struggle for Indian independence.

To admirers such as the Rev. Martin Luther King Jr., Gandhi’s stand against the British Empire epitomized discipline in a righteous cause. Churchill, meanwhile, bitterly opposed Gandhi’s movement and once denounced him as “an enemy of the Empire.”

Some activists today, however, disparage Gandhi almost as much as Churchill. Discounting his achievements, they focus instead on the odious racist attitudes he expressed toward Black South Africans when he lived in that country around the turn of the 20th century.

Statues of Gandhi in Washington and Amsterdam, like Churchill’s in London, have been vandalized; in several British cities, there have been calls, rejected so far, for officials to take down similar images.

The global movement for racial justice is generating a long-overdue reckoning with painful truths, both contemporary and historical.

One such truth is that Winston Churchill was a British imperialist to his core, with all the prejudices and bellicosity that implies. It is also true that Churchill, defying long odds and much conventional wisdom, waged uncompromising war on the worst, most dangerous, racist regime there ever was.

In a long, complex and sometimes baleful career, it was indeed his finest hour, worthy of a monument — or two.

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