Battle of Britain

When the continent collapsed, the island's defence was put to the test

On the morning of 10 May 1940, Britain's crisis was not simply that the German air force had become stronger. When war began in September 1939, Britain had expected to blockade Germany with France and contain it on the continent. By the spring of 1940, however, the war was turning into a long air-defence struggle over Britain itself. German forces drove through the Netherlands and Belgium, struck the weak point in the French front, crossed the Meuse with armoured formations, and raced toward the Allied rear and the Channel. The British Expeditionary Force became trapped in the north alongside the French army. Even if it escaped from Dunkirk, it would have to leave behind artillery, vehicles, and ammunition. When French Prime Minister Paul Reynaud telephoned Winston Churchill on 15 May and said, “We have been defeated; we have lost the battle,” he was reporting not merely low morale, but the collapse of the Allies’ operational system.

Britain had already built a separate organisation for defending its skies. Established in 1936, RAF Fighter Command under Hugh Dowding was tasked with preserving a limited fighter force for decisive points at home rather than treating fighters and bombers as interchangeable instruments. Against the widespread belief that “the bomber will always get through,” Dowding argued that early warning and ground control could intercept raids without keeping fighters constantly in the air and wasting them. His conception was more than a radar device. When Chain Home stations, the low-altitude detection network, and the volunteer Observer Corps found a raid, information was filtered at Bentley Priory, then passed through four Groups and their sector operations rooms, which directed Hurricanes and Spitfires by radio. The system was not flawless. Bombers crossing the coast entered radar gaps, and observer reports could misjudge height and strength. Nevertheless, it replaced continuous patrols with timely interception, conserving fuel, aircraft, and pilots.

The political pressure on 10 May therefore came from two directions. Allied commanders wanted British fighters and bombers sent to France to hold the continent, while Dowding warned that further diversion could endanger the defence of Britain itself. The RAF suffered heavy losses in the Battle of France, and Britain was left facing German airfields and bombers with fewer allies and little strategic depth. Yet German victory did not automatically make Britain surrender. The choice before the British government was no longer simply how to recover the continent, but how to preserve an air-defence network and industrial capacity capable of resisting the next pressure intended to remove the island from the war. The Battle of Britain began from this contradiction: whether to save the ally on the continent or conserve the means to defend Britain at home.