Operation Gomorrah was the military codename for a series of air raids conducted by the British air force on the city of Hamburg beginning in the end of July 1943. It was at the time the heaviest assault in the history of aerial warfare.
The operation was originally formulated by British Air Marshall Arthur Travers Harris and was actually a joint effort between the R.A.F. and the United States Army Air Force (specifically 8th Air Force Bomber Command), who combined to create an "around-the-clock" bombing mission spanning 3 days and 2 nights--the Americans conducting the daylight raids with the British following after nightfall. In the night of July 27/28, owing to unusually warm weather, along with the deliberate planning of the raids (which trapped the city's firefighters in the bombed-out center of the city by following-up with incendiary bombing of the periphery), the bombings culminated in the spawning of the so-called "Feuersturm" (firestorm). Quite literally a tornado of fire, this phenomenon created a huge outdoor blast furnace, containing winds of up to 150 mph (240 km/h) and reaching temperatures of 1500 degrees Fahrenheit (800 degrees Celsius). It caused street asphalt to burst into flame, cooked people to death in air-raid shelters, sucked pedestrians off the sidewalks like leaves into a vacuum cleaner and incinerated some eight square miles (21 km²) of the city. Operation Gomorrah occasioned at least 50,000 deaths and left over one million German civilians homeless.