On 15 September 1940, the Luftwaffe launched its largest, most concentrated attack against London.
Known as Battle of Britain Day, this pivotal clash saw the German Luftwaffe attempt to annihilate the Royal Air Force to clear the way for a land invasion. Despite the intensity of the assault, the RAF's defensive strategy ultimately forced the Luftwaffe to abandon its plans for Operation Sea Lion.
By mid-September 1940, Nazi Germany had conquered much of Scandinavia and Western Europe, leaving Great Britain as the primary obstacle to total domination. Adolf Hitler ordered the Luftwaffe to destroy the Royal Air Force (RAF) to achieve air superiority, a necessary precursor to Operation Sea Lion, an amphibious invasion of the British mainland. Following a series of attacks on airfields and ports that began on 10 July, Hitler shifted the focus to London in early September, hoping to draw the RAF into a decisive battle that would cripple its defensive capacity.
The climax arrived on 15 September. Luftwaffe planners designed a two-pronged strike targeting London's railway infrastructure and the Thames Estuary docklands. German intelligence, misled by the apparent success of earlier raids, believed the RAF was on the verge of collapse. However, the RAF had maintained its strength far better than expected. On the evening of 14 September, Fighter Command could still muster over 500 fighters across its two key groups. Air Vice Marshal Keith Park, commanding No. 11 Group, employed a strategy of constant, moderate opposition to safeguard his airfields, while Air Vice Marshal Trafford Leigh-Mallory of No. 12 Group pushed for larger 'Big Wing' formations to intercept the enemy.
During the 15 September daylight battles, approximately 1,500 aircraft participated. The Luftwaffe faced significant challenges, including heavy attrition, fuel limitations for its Bf 109 escorts, and a large cloud base that dispersed its formations. Prime Minister Winston Churchill observed the operations from RAF Uxbridge as the RAF successfully disrupted the German approach. The Luftwaffe failed to inflict severe damage on London, and the failure to secure air superiority led to the indefinite postponement of Operation Sea Lion. This defeat forced the Luftwaffe to shift its strategy toward the night-time Blitz campaign, marking a turning point in the war.
Source: Battle of Britain Day
