incendiaries went into service with the 8th Bomber Command shortly before the Hamburg raid – this was preferred by the Americans to the magnesium-cased thermite bomb used by the British. It is clear that the effectiveness of the Hamburg raid relied to a large extent on the careful research on how best to cause a large fire in a German city – as opposed to the popular view that it was some sort of accidental occurrence due to unusual weather conditions. Target selection A number of factors led to Hamburg being chosen for the planned firebombing raid. The construction of the city meant its vulnerability was considered "outstanding". It was Germany's second largest city. The city's shipbuilding industry made it a priority target. It also had more industrial targets of interest to the Ministry of Economic Warfare than most other German cities. It was reasonably close to the bomber bases in Britain, so giving a short flight, with less exposure to anti-aircraft fire and fighters. Hamburg's position, close to the coast and on a prominent river made the target easy to find. Significant missions Battle of Hamburg The Battle of Hamburg, codenamed Operation Gomorrah, was a campaign of air raids which began on 24 July 1943 and lasted for 8 days and 7 nights. It was at the time the heaviest assault in the history of aerial warfare and was later called the Hiroshima of Germany by British officials. Until the focus of RAF Bomber Command switched to Hamburg, their focus had been on the Ruhr industrial region which had been the target of a five-month-long campaign. The operation was conducted by RAF Bomber Command (including RCAF, RAAF and Polish Squadrons) and the USAAF Eighth Air Force. The British conducted night raids and the USAAF daylight raids. The initial attack on Hamburg included two new introductions to the British planning: they used "Window", later known as chaff, to confuse the German radar, while the Pathfinder Force aircraft, which normally kept radio silence, reported the winds they encountered, and this information was processed and relayed to the bomber force navigators. No. 35 Squadron led the target marking and, thanks to the clear weather and H2S radar navigation, accuracy was good, with markers falling close to the aiming point. On 24 July, at approximately 00:57, the first bombing started by the RAF and lasted for almost an hour. The confusion caused to