312 aircraft - 241 Halifaxes, 62 Lancasters, 9 Mosquitos - of Nos 4, 6 and 8 Groups attacked Hamburg. 1 Halifax lost. The purpose of this raid was to hit the shipyards which were now assembling the new Type XXI U-boats, whose parts were prefabricated in many parts of inland Germany. Thanks to the Schnorkel breathing tube and a new type of battery-driven electric engine, the Type XXI could cruise under water for long periods and was capable of bursts of high speed. Its development in numbers would have posed great problems for Allied convoy defence if the war had lasted longer. The Hamburg area was found to be cloud-covered and the bombing was not expected to be accurate enough to cause much damage to the shipyards.
