Germany Begins Air Raids on the Port of London

The first intentional air raids on London were mainly aimed at the Port of London, causing severe damage. Late in the afternoon of 7 September, 364 bombers attacked, escorted by 515 fighters. Another 133 bombers attacked that night. Many of the bombs aimed at the docks fell on neighbouring residential areas, killing 436 Londoners and injuring 1,666.

Few anti-aircraft guns had fire-control systems, and the underpowered searchlights were usually ineffective against aircraft at altitudes above 12,000 feet (3,600 m). Even the fortified Cabinet War Rooms, the secret underground bunker hidden under the Treasury to house the government during the war, were vulnerable to a direct hit. Few fighter aircraft were able to operate at night, and ground-based radar was limited. During the first raid, only 92 guns were available to defend London. The city's defences were rapidly reorganised by General Sir Frederick Pile, the Commander-in-Chief of Anti-Aircraft Command, and by 11 September twice as many guns were available, with orders to fire at will. This produced a much more visually impressive barrage that boosted civilian morale and, though it had little physical effect on the raiders, encouraged bomber crews to drop before they were over their target.

During this first phase of the Blitz, raids took place day and night. Between 100 and 200 bombers attacked London every night but one between mid-September and mid-November. Most bombers were German, with some Italian aircraft flying from Belgium. Birmingham and Bristol were attacked on 15 October, and the heaviest attack of the war so far – by 400 bombers and lasting six hours – hit London. The RAF opposed them with 41 fighters but only shot down one Heinkel bomber. By mid-November, the Germans had dropped more than 13,000 tons of high explosive and more than 1 million incendiary bombs for a combat loss of less than 1% (although some aircraft were lost in accidents inherent to night flying and night landing).

Hitler's No. 17 Directive, issued 1 August 1940 on the conduct of war against England specifically forbade Luftwaffe from conducting terror raids on its own initiative, and reserved the right of ordering terror attacks as means of reprisal for the Führer himself, despite the raids conducted by RAF Bomber Command against German cities since May 1940. This echoed Göring's general order issued on 30 June, 1940 on the air war against the island fortress:

The war against England is to be restricted to destructive attacks against industry and air force targets which have weak defensive forces.... The most thorough study of the target concerned, that is vital points of the target, is a pre-requisite for success. It is also stressed that every effort should be made to avoid unnecessary loss of life amongst the civilian population.

The Luftwaffe offensive against Britain had included numerous raids on major ports since August, but Hitler had issued a directive London was not to be bombed save on his sole instruction. However, on the night of 23 August, bombs were accidentally dropped on Harrow on the outskirts of London as well as raids on Aberdeen, Bristol and South Wales. The focus on attacking airfields had also been accompanied by a sustained bombing campaign which begun on 24 August with the largest raid so far killing 100 in Portsmouth, and that evening the first night raid on London as described above. On 25 August 1940, 81 bombers of Bomber Command were sent out to raid industrial and commercial targets in Berlin. Cloud prevented accurate identification and the bombs fell across the city, causing some casualties amongst the civilian population as well as damage to residential areas. Continuing RAF raids on Berlin in retaliation led to Hitler withdrawing his directive, and on 3 September Göring planned to bomb London daily, with Kesselring's enthusiastic support, having received reports the average strength of RAF squadrons was down to five or seven fight...