In the first months of the war, British strategic bombing (aerial attacks on the enemy's industry and infrastructure) were bound by the belief that deliberate attacks on civilians and private property were illegal and unjustifiable. By 1945, RAF Bomber Command was obliterating historic German cities overnight. It was a terrifying transformation in the nature of war, that saw industrial towns across Europe smashed to pieces and hundreds of thousands of civilians killed.
When Luftwaffe night-bombers unintentionally (and against orders) attacked London in August 1940, Churchill ordered a retaliatory raid on Berlin. This caused an enraged Hitler to order intensified bombing of targets in and around London.
Both sides thus claimed that their attacks on enemy cities were in retaliation for what had been begun by the enemy. In reality, the bombing of cities and their civilian population had been a reality of warfare since the First World War. In 1940, both sides were intent on attacking the enemy's economic resources. These were mostly concentrated in cities, and given the inaccurate nature of bombing in World War Two (especially at night), this policy would inevitably lead to the destruction of houses and many civilian deaths.
In February 1942, RAF Bomber Command explicitly began to focus its attacks on the enemy civilian population, when it shifted from strategic bombing to the night-time area bombing of cities, designed to break enemy morale. Arthur 'Bomber' Harris, the new head of Bomber Command, saw civilian death (or the 'dehousing' of the German workforce) as entirely necessary. He felt that despatching 1,000 aircraft each night against German objectives, destroying great industrial cities in hours, would render the invasion of Europe unnecessary. He pointed to the Cologne raid of May 1942 as an example of what could be achieved: in one night, 1,046 aircraft rained more than 2,000 tons of bombs on the city, reducing 13,000 houses to rubble.
The US Army Air Force, flying raids from British bases from 1942, remained faithful to the concept of precision daylight bombing (with variable accuracy). 'Around the Clock' offensives began - RAF by night , USAAF by day.
Early daylight raids by the USAAF, without the protection of long-range fighter escorts, could lead to terrible losses. The Schweinfurt raid, an attack on ball-bearing factories designed to create 'choke-points' in German industry, led to the loss of 77 B-17 bombers, about one quarter of the attacking force. Such long-distance raids were then abandoned until 1944, when long-distance fighter escorts were available.
In May 1943, RAF Bomber Command was able to pull off one stunning piece of precision bombing, in the famous Dambusters raids against dams in the Ruhr Valley, in the German industrial heartland. Although the economic impact of the raid was negligible, it was a skilful and courageous operation that had a great impact on public morale.
Meanwhile, area bombing continued. In June 1943, in Operation Gomorrah, British and American bombers attacked Hamburg day and night for an entire week; half the city was levelled, and 40,000 were killed. In January 1944, the RAF pummelled Berlin. On 11 December, Frankfurt, Hanau and Giesson were levelled by 1,600 American planes. In January 1945, the USAAF dropped almost 40,000 tons of bombs on Berlin, Cologne and Hamm, while the RAF hit Bochum, Munich and Stuttgart.
By the war's last months, virtually every important German industrial town had been destroyed. Yet the bombing continued. Churchill, convinced that destroying East German communication centres would aid the Red Army's advance on Berlin, authorised the bombing of Dresden. On 13-14 February 1945, around 30,000 civilians were killed in attacks by the RAF and the USAAF.
The effectiveness of the bombing campaign is still debated. There was terrible destruction of the German economy, although output still rose during the war as the economy was geared more and more towards wartime needs. Public support in Germany for the Nazi regime, and civilian morale, was not obviously affected. The bombing campaign did force Germany to devote huge resources to the defence of the homeland, and the German air force suffered significant losses at the hands of Allied fighter escorts. The US Eighth Air Force and RAF Bomber Command paid a high price. Six in ten British bomber aircrew were killed, one of the highest casualty rates of any service in the war.