The stage for the battle was set in May 1940, when Nazi Germany launched a massive blitzkrieg against Western Europe. Hitler’s armies overran Belgium, the Netherlands and France in only a matter of weeks, leaving Britain as the lone standing Allied power. During a June 18 speech, Prime Minister Winston Churchill predicted a showdown with Germany when he said, “The Battle of France is over. I expect the Battle of Britain is about to begin.”

Despite being fresh off his lightning conquest of France, Hitler was wary of invading Britain. The English Channel, protected the island nation and its Royal Navy was superior to the German Kriegsmarine. He instead hoped that Britain would acknowledge “her militarily hopeless situation” and sue for peace.

A small contingent of British politicians also favored a compromise, but Winston Churchill brushed off talk of surrender and announced that Britain was determined to fight on. He rallied the public by characterizing the coming battle as a struggle for national survival, and when the Nazis dangled the prospect of a peace treaty in early July 1940, he rejected it outright. It was only then that Hitler reluctantly approved plans for Operation Sea Lion, an amphibious invasion originally scheduled to unfold in mid-August.

Hitler’s plan to invade the British mainland hinged on Germany first annihilating the Royal Air Force and winning air superiority over Britain. With this in mind, the fight for Britain transformed into an all-air contest between the Luftwaffe’s bombers and Messerschmitt Bf109s and British Fighter Command’s Hawker Hurricanes and Supermarine Spitfires. Luftwaffe commander Hermann Goering initially believed he would easily sweep the RAF aside in just a few days, but the dogfights dragged on for three and a half long months. By the time the battle ended in late October, Germany had lost more than 1,700 planes—nearly twice as many as the British.

While the Luftwaffe enjoyed an edge in total aircraft during the early stages of the battle, the RAF had a secret weapon in the form of Radio Direction Finding, better known as radar. Shortly after the technology was developed in the 1930s, the British built a ring of radar stations along their coastline. These “Chain Home” stations were still primitive—a civilian Observer Corps was required to spot low-flying aircraft—but they nevertheless became a crucial part of Britain’s strategy.

By pinging approaching Luftwaffe raiders with radio waves, the RAF could pin down their location and scramble fighters to intercept them, thereby robbing the Germans of the element of surprise. Nazi leaders never appreciated the importance of British radar, and their failure to degrade it allowed the RAF to consistently remain a step ahead of the Luftwaffe.

Of the more than 2,900 RAF pilots who served in the Battle of Britain, only around 2,350 were British. The rest were natives of Commonwealth territories such as Canada, Australia, New Zealand and South Africa, as well as expatriates from Poland, Czechoslovakia, Belgium and other countries under Nazi occupation. There were even a handful of American pilots, most notably Billy Fiske, a 29-year-old sportsman who had previously won a gold medal for bobsledding at the Winter Olympics. The international contingent proved especially deadly in the cockpit. The Polish No. 303 fighter squadron downed 126 German planes during the battle—more than any Allied unit—and the RAF’s top-scoring ace was Josef Frantisek, a Czech aviator who singlehandedly claimed 17 aerial victories.

For men on both sides of the Battle of Britain, combat fatigue was as persistent a foe as enemy Spitfires and Messerschmitts. German morale sank to dangerous lows as the battle wore on, and British airmen were beaten down by grueling 15-hour shifts and constant Luftwaffe bombing raids on their airfields.

Pilots often flew several missions a day on only a few hours of sleep, and many took amphetamine pills just to keep themselves awake. In a bid to bolster its used up fighter force, the RAF eventually cut the training time for new pilots from six months to just two weeks. Some recruits even ended up on the front lines with as little as nine hours’ experience in modern fighter planes.

During one of the battle’s most frantic periods of fighting over London, RAF Sergeant Ray Holmes spotted a German Dornier bomber headed in the direction of Buckingham Palace. Holmes had already used up all his ammunition in an earlier dogfight, but rather than retiring, he steered his Hawker Hurricane straight at the enemy aircraft and rammed it with his wing.

The blow sliced the Dornier’s tail clean off and sent it plummeting into nearby Victoria Station. Holmes’ Hurricane was also wrecked, but he managed to bail out and land dangling from the roof of an apartment complex. The astonishing incident was partially captured on film, and Holmes was hailed as a national hero for having saved the royal residence from potential disaster.

Thanks to its sleek lines and blistering speed, the Supermarine Spitfire has gone down in popular lore as the plane that saved Britain during the Battle of Britain. Yet Spitfires only made up a third of the British fighters during the campaign. The bulk of the RAF force consisted of the less glamorous Hawker Hurricane, an older wood-and-fabric fighter that was slower than the Spitfire but reportedly sturdier and more forgiving in combat. While the two planes carried the same armaments, the Hurricane’s superior numbers meant that it was responsible for the vast majority of Luftwaffe losses during the battle.

The Luftwaffe’s bombing campaigns in Britain were initially restricted to military and industrial targets, but the strategy changed in September 1940, after the RAF launched a retaliatory raid against Berlin. The strike sent Hitler into a fit of rage. Ignoring the progress the Luftwaffe was making in attacking RAF air bases, he demanded they shift their focus toward “erasing” British cities from the map. The bombing campaign now known as the Blitz began on September 7 with a raid on London, and dozens more attacks followed over the next several weeks.

While the bombings took a sobering toll on British civilians, they also temporarily relieved pressure on the RAF, allowing it to repair its crippled airfields and refresh its pilots. The respite proved critical. When the Luftwaffe tried to score a knockout blow with a massive air attack on September 15, a resilient RAF intercepted them and downed roughly 60 aircraft. Hitler was forced to shelve Operation Sea Lion only a few days later.

The Battle of Britain fizzled out in late-October 1940, when Hitler abandoned his quest for control of British airspace and turned his attention toward attacking the Soviet Union. The campaign was Germany’s first major defeat in World War II, but it didn’t mark the end of the Blitz against Britain. The Luftwaffe continued to conduct nighttime bombing raids over London, Coventry and other cities for several more months in a futile attempt to break Britain’s fighting spirit. By the time the campaign finally ended in May 1941, some 40,000 people had been killed.