An offensive against the Rhine-Ruhr area ("Happy Valley" to aircrew) began on the night of 5/6 March 1943, with the first raid of the Battle of the Ruhr on Essen. The bombers destroyed of the city and hit 53 Krupps buildings. The Battle of Hamburg in mid-1943 was one of the most successful Bomber Command operations, although Harris' extension of the offensive into the Battle of Berlin failed to destroy the capital and cost his force more than 1,000 crews in the winter of 1943–44. In August 1943, Operation Hydra, the bombing of the Peenemünde V-2 rocket facility opened the secondary Operation Crossbow campaign against long-range weapons.