July – October 1940

The air defence of Britain in the Second World War relied on a modern web of electronic communication and detection. Here WAAFs in the Operations Room of 10 Group Headquarters at Rudloe Manor in Wiltshire plot the flight paths of incoming aircraft.

In the late summer of 1940, one of the most important battles of the Second World War was fought out between the British Royal Air Force and the German Luftwaffe in the skies over southeastern England. Since the start of the war in September 1939, the German armed forces had defeated and occupied seven European states – Poland, Norway, Denmark, The Netherlands, Belgium, Luxembourg and France. Britain had sent an army to France to help defend against a German attack, but it was defeated and expelled from continental Europe in late May and early June 1940. German forces occupied northern France and the Low Countries and prepared for the next war of conquest against Britain. The German leader Adolf Hitler, who was also the supreme commander of the German armed forces, planned to invade southern England with Operation Sea Lion, but first he needed his large air forces, stationed in northern France and the Low Countries, to defeat the RAF so that the Channel crossing and the capture of beachheads in Kent and Sussex could be achieved with a reduced threat from the air or from the Royal Navy. Upon the outcome of the air battle depended the future of democratic Europe. A British defeat would mean a German hegemony in Europe; a British success would not defeat Hitler, but it would keep resistance alive. The battle hinged on whether the new technology available to the RAF would work effectively.

The Battle of Britain did not resemble a land battle with a clear shape and a definitive day on which victory was secured. It was a battle of attrition that went on throughout the summer and autumn months. The German aim was to destroy RAF Fighter Command in a few days and then to deploy the large German bomber force to knock out military and economic targets in southern Britain before attempting a landing. The day chosen by the Luftwaffe commander-in-chief, Hermann Göring, for the start of the campaign, codenamed ‘Eagle Day’, had to be postponed because of poor weather, and the date eventually chosen, 13 August, was less than ideal for flying. Half the force was called back, and in the end the full weight of the German air attack was brought to bear only on 18 August against Fighter Command targets, and particularly the fighter stations of Air Vice Marshal Keith Park’s 11 Group in southeast England. For the next two weeks repeated attacks were made on fighter stations but despite repeated bombing only three were closed, and then only for a short time. Every day RAF aircraft took a heavy toll on attacking fighters and bombers. Although German air intelligence regularly reported that the RAF was close to collapse, the Spitfire and Hurricane fighters appeared every day ready to meet the incoming German aircraft.

The Germans never guessed that the secret of the RAF’s success that summer lay in a complex network of communication based around the use of radio direction finding (RDF or ‘radar’), which had been developed in Britain from 1935. Other countries developed it too, but none applied it so systematically to aerial defence. By 1940, a chain of twenty-one radar stations had been set up around Britain’s southern and eastern coastlines for detecting high-flying aircraft, and thirty-six so-called Chain Home Low stations to detect aircraft flying lower than 300 metres (1,000 feet). The information from the stations was fed to a central Fighter Command operations room at Bentley Priory just north of London, where the commander-in-chief of Fighter Command, Air Chief Marshal Sir Hugh Dowding, had his headquarters. It was sent on to the Fighter Group headquarters and from there to individual sector stations. Information had to be transferred in a matter of minutes to give fighters time to scramble into the air to intercept, and it relied on a strategic set of telephone cables, laid by the General Post Office, that held the whole communications structure together. The system did not always work perfectly, but it ensured that the RAF could use its fighters sparingly. They would be in the right place rather than flying long patrols with no knowledge of enemy movements. The Luftwaffe assumed that RAF fighters were tied inflexibly to the area around their bases, and never realized that the presence of British aircraft was achieved through a vital scientific breakthrough. Without the system of central control and early warning, Germany’s air fleets might well have inflicted irreparable damage.

The Supermarine Spitfire was the iconic aircraft of the Battle of Britain. Armed with eight machine guns, it had great speed and manoeuvrability and became the mainstay of RAF Fighter Command throughout the war.

The German side consistently exaggerated the damage being done to the RAF. By September, Fighter Command, with over 700 aircraft, had more fighters operationally available than it had had when the battle started, and there were never fewer than 1,400 pilots on hand. The Luftwaffe suffered from poor supply from German factories of aircraft and bombs and a slow, if thorough, training system. In the last weeks of combat the German fighter force was down to 700–800 operational pilots and 600 aircraft. The combination of radar, an effective communication system and a regular resupply of RAF planes and pilots ensured that the German side could not win air superiority over southeast England, even though the RAF had its own weaknesses in the quality of fighter armament and the rigid flying pattern initially adopted by fighter units.

On 7 September, the Luftwaffe switched the weight of attack to London in preparation for Operation Sea Lion, but lost so many aircraft over the week that followed that daylight bombing had to be abandoned. On 15 September, now celebrated as Battle of Britain Day, one-quarter of the Luftwaffe’s forces were shot down or damaged. This was a level of loss no force could sustain and 15 September, the day Hitler had originally planned to invade, marked the end of the major daylight air battles, and the end of the invasion threat to Britain. On 17 September, Hitler postponed Sea Lion indefinitely. During October, the German fighter force undertook regular hit-and-run raids to lure the RAF into combat, but they petered out by the end of the month. Over the course of the battle from July until the end of October, the Luftwaffe lost 1,733 planes, RAF Fighter Command 915. Radar became one of the most important technical developments of the Second World War, a classic example of how a technical lead, even a temporary one, can transform the face of battle. Radar was also used in the anti-submarine campaign and in all the air battles of the war, and laid the foundation for today’s electronic battlefield.