On June 18, 1940, Sir Winston Churchill announced that France had fallen to the Nazis. The date marked the beginning of the Battle of Britain.

“Let us therefore brace ourselves to our duty, and so bear ourselves that if the British Empire and its Commonwealth last for a thousand years, men will still say, ‘This was their finest hour.'”

Next, Hitler turned his attention to England. The Soviet Union was on Germany’s side. America watched from the sidelines. England stood alone, and the Nazis almost won.

But Hitler misjudged the indomitable British character.

The courage and resilience of Britain’s ordinary people in 1940 — from Dunkirk through the London Blitz — is examined in a gritty, poignant and often heartbreaking documentary airing this month on PBS-TV.

“Finest Hour” is the most emotionally moving sort of television: four hours of history told by those who lived through it. But despite the dark moments, the spirit with which they faced their ordeal is uplifting.

Take Bess Walder, for example. She was 15 in 1940 and her brother was 9. When the bombing of Britain began, her parents decided to send their children to Canada, so they’d be safe. “Grow up to be a good girl,” her mother told her as she and her brother boarded the train for Southampton. It took Bess a while to figure out what her mother meant: that she might never see her daughter again.

In the middle of the Atlantic, The Germans sank the ship that was taking Bess and her brother to Canada. Bess and others managed to get away in lifeboats, but soon the one Bess was in capsized. When Bess surfaced, there — miraculously — was the lifeboat, but it was upside down. Bess and another girl named Beth managed to cling to it nevertheless. “We were not in the business of giving up,” she says.

Bess is not sure to this day how long she and Beth clung to the lifeboat, but it was for some time — long enough for her to lose hope of being rescued and to begin contemplating death.

Then came the second miracle. A ship, H.M.S. Hurricane, appeared on the horizon. Soon a sailor was reaching for her. “Come on, darling, let go,” he said.

“And you know,” she says, “I couldn’t. My hands were stuck tight.” The sailor forced her fingers open, and she was rescued.

And finally, a third miracle: Her brother, whom she hadn’t seen since the ship sank, was also saved by H.M.S. Hurricane.

Edith Heap, who served as a Waaf, sums up the meaning of courage, too, when she discusses the young men who flew in the Battle of Britain: “The brave ones — the very brave ones — were the ones who were terrified, and went anyway.”

“Finest Hour” is surely four of the finest hours of documentary television you’ll see this summer.