As a large city and industrial centre, Hamburg's shipyards, U-boat pens, and the Hamburg-Harburg area oil refineries were attacked throughout the war.

[1] As part of a sustained campaign of strategic bombing during World War II, the attack during the last week of July 1943, code named Operation Gomorrah, created one of the largest firestorms raised by the Royal Air Force and United States Army Air Forces in World War II,[2] killing an estimated 37,000 people in Hamburg,[3] wounding 180,000 more,[citation needed] and destroying 60% of the city's houses.

[3] Hamburg was selected as a target because it was considered particularly susceptible to attack with incendiaries, which, from the experience of the Blitz, were known to inflict more damage than just high explosive bombs.

Hamburg also contained a high number of targets supporting the German war effort and was relatively easy for navigators to find.

[4] The unusually warm weather and good conditions ensured that the bombing was highly concentrated around the intended targets, and helped the resulting conflagration create a vortex and whirling updraft of super-heated air which became a 460-metre-high (1,510 ft) tornado of fire.

The extent of this failure was exposed to the War Cabinet in August 1941 by the Butt Report, which by analysing 600 photographs of raids in the previous three months, found that only a third of crews that claimed to have reached their targets had actually dropped their bombs within five miles (8.0 km) of them.

The absenteeism of de-housed workers was considered to have a bigger effect on industrial production than the level of damage that could be caused, with the same effort, to the factories in which they worked.

[7] The build up of the 8th Bomber Command was slow and though some small scale raids were made in France during the latter half of 1942, capability to attack Germany was not obtained until 1943.

[8] By the time of the big raid on Hamburg at the end of July 1943, both air forces needed a significant success to justify their existence.

Large quantities of US-made oil-based incendiaries went into service with the 8th Bomber Command shortly before the Hamburg raid – this was preferred by the Americans to the 4 lb (1.8 kg) magnesium-cased thermite bomb used by the British.

Operation Gomorrah was carried out by RAF Bomber Command (including RCAF, RAAF and Polish Squadrons) and the USAAF Eighth Air Force.

35 Squadron led the target marking and, thanks to the clear weather and H2S radar, accuracy was good, with markers falling close to the aiming point scattered over five districts.

During the raid a large (6-mile) creepback developed which saved the city centre from catastrophe but caused other districts to the north to be set on fire as well.

[16] During the early stages of the raid, some bombs fell on the Blohm and Voss shipyard, where three U-boats were destroyed: U-1011 and U-1012 were hit on their slipways and never repaired, and U-996 sank at the dockside.

Despite being partly covered in smoke from the previous night bombing, some buildings in the shipyard were hit but the vital U-boat construction slipways were not damaged.

Over the North Sea on the way back to bases, the formation was attacked by eight night-fighters operating from Holland but they achieved nothing, whilst losing one of their number[20] Air reconnaissance on 25 July at 18:30 revealed that Hamburg was still covered in smoke from the previous raids, so another attack by the main force of bomber command on Hamburg for that night was cancelled and instead 705 bombers raided Essen that night.

139 Squadron RAF Light Night Striking Force (LNSF) carried out a nuisance raid in order to keep the city on a state of alert.

The tornadic fire created a huge inferno with winds of up to 240 km/h (150 mph) reaching temperatures of 800 °C (1,470 °F)[28] and up to altitudes in excess of 300 metres (1,000 ft), incinerating more than 21 square kilometres (8 sq mi) of the city.

Asphalt streets appeared to burst into flame (in fact, it was the phosphorus from the fire bombs that was burning), and fuel oil from damaged and destroyed ships, barges and storage tanks spilled into the water of the canals and the harbour, causing them to ignite as well.

The Germans did not record specific data for this raid, the number of victims is unknown but on this night 370 people died by carbon monoxide poisoning in a large public shelter.

Just before reaching the German coast, the bomber stream met a severe storm which forced many aircraft to abort or to bomb alternative targets.

In some cases, the numbers of people who had perished in cellars converted into "air protection rooms" could only be estimated from the quantity of ash left on the floor.

The fighting fronts suffered due to a lack of air support as resource was devoted to fighter aircraft back in the Reich.

[56][57] The destruction of Hamburg became a major news story at the time and caused a great impression as to the extent of the damage and loss of life.

By 3 August 1943, just as the raids were concluding, military expert George Fielding Eliot was analyzing the subject at length in his syndicated column published in US newspapers.

[60] At the same time in Germany itself, the Hamburg raids were seen as a far worse development than major German military reverses then taking place on the Eastern Front and in Sicily and Italy.

[61] Initial eyewitness accounts by foreign nationals who had been in Hamburg did not attempt to give numerical figures for the destruction, instead describing it as beyond belief.

[62][63] As one 9 August 1943 United Press story about a Swiss merchant's account related, it was a "hell released" by a "devil's concert" that amounted to "Hamburg's ceaseless, inescapable destruction on a scale that defies the imagination.

[64] By November 1943, a Swiss dispatch to Swedish newspapers gave a figure of 152,000 killed in the Hamburg bombing, but without supplying an explanation for the source of the number.

Objecting to this line of reasoning, Senator Brien McMahon, chairman of the United States Congressional Joint Committee on Atomic Energy, wrote a letter to President Harry S. Truman in which he asked, "Where is the valid ethical distinction between the several Hamburg raids that produced 135,000 fatalities," the March 1945 firebombing of Tokyo, the atomic bombing of Hiroshima, and the proposed thermonuclear weapon.