“The gratitude of every home in our Island, in our Empire, and indeed throughout the world, except in the abodes of the guilty, goes out to the British airmen who, undaunted by odds, unwearied in their constant challenge and mortal danger, are turning the tide of the World War by their prowess and by their devotion. Never in the field of human conflict was so much owed by so many to so few.” — Winston Churchill addressing England’s House of Commons, August 20, 1940

Of the countless memorable phrases uttered by the indomitable British Prime Minister during the war years, Winston Churchill’s tribute to and celebration of “The Few,” as the airmen of the Royal Air Force have ever since been affectionately known, endures as among his most moving and most heartfelt. (That not all of the pilots were, in fact, British — there were Poles, Czechs, Americans, Canadians, Irish, New Zealanders and others, as well — that fact hardly dilutes the power of the sentiment, or the intensity of Churchill’s and England’s gratitude to those fliers.)

In 1940′s pivotal, four-month Battle of Britain, thousands of these (mostly young) pilots held off fighters from the mighty German Luftwaffe, quite literally saving the Sceptered Isle from defeat at the hands of the Third Reich and proving to a skeptical world that the Nazi military juggernaut was neither inevitable nor invincible.

Here, as Battle of Britain Day approaches — commemorating a major, pivotal RAF victory in the early summer of 1940, when close to 1,500 aircraft from both sides fought for supremacy in the skies above England — LIFE.com offers charming, revealing portraits of The Few by LIFE photographer William Vandivert. (Note that most of these photos did not originally appear in the magazine.)

As LIFE put it to its readers the following spring, when the magazine ran some of Vandivert’s pictures in the March 21, 1941, issue:

England’s most important young men today are the several thousand youth who fly the Hurricane and Spitfire fighters in the Battle of Britain. They undoubtedly saved England last fall from Nazi invasion. Hitler must knock them all out of the air over Britain before he dares to invade England this spring.

[In these pictures] LIFE takes you to an actual airfield of the RAF’s Fighter Command during the airblitz last fall. Here you see new kind of battle action — what goes on on the ground at a fighter station while the fate of a nation is being fought out in the clouds.

These young British fliers, unlike their German opponents, are elaborately modest. There is little or no brag and swagger about them and they fight the Germans with a sort of casual perfection that is the envy of every other air force in the world. Their job calls for a fit young man of great calm and great optimism, preferably not in love. Very few of these young fighter pilots are married. Their ages range around 23. It takes moral self-confidence and concentration to kill early, often and quickly, without a sense of guilt.

Close to 3,000 RAF fliers took to the skies in the Battle of Britain. More than 500 were killed; around 80 percent of those lost were Britons. The chance of any of The Few ever being forgotten by the nation they helped save, meanwhile, is absolutely zero.