Operation Gomorrah (24 July-3 August 1943), also known as the Battle of Hamburg, was a week-long bombing raid carried out by the Royal Air Force and the US Air Force against the northern German city of Hamburg. 50,000 German civilians were killed in a firestorm that was nicknamed "the Hiroshima of Germany" by future British historians.
The British Royal Air Force had adopted nighttime bombing because their aircraft could not survive over Nazi Germany in daylight. These bombings were inaccurate, so the British launched mass attacks with fleets of heavy bombrers against cities, hoping that the sheer scale of destruction would deliver a decisive blow. By contrast, the US Air Force was committed to precision raids on industrial and military targets. In the summer of 1943, the USAF and the RAF launched a combined attack on the port city of Hamburg, with the RAF attacking at night and American B-17s attacking by day. The Germans developed a defense system, consisting of radar operators on the ground who tracked the bombers and guided night fighters on to their targets. Antiaircraft fire was also directed by radar; the RAF developed a new countermeasure known as "window", in which the bombers scattered strips of aluminum foil to confuse the German radar and leave the night fighters and flak guns blind. On the night of 27-28 July 1943, 735 British bombers dropped 2,326 tons of explosives and incendiaries in just over an hour, and the bombardment, aided by weather conditions, generated a firestorm that swept through the city and killed an estimated 46,000 people.