New construction procedures, dispensing with prototypes and the abandonment of modifications reduced construction times from 460,000-man hours to 260–300,000 to meet Speer's quota. In the spring 1944, the Type XXI submarine was scheduled to reach frontline units. In 1943 however, the Combined Bomber Offensive complicated the planned production. Dönitz and Speer were appalled by the destruction of Hamburg, a major construction site. The battles of 1943 and 1944 were fought with the existing VII and Type IX submarines. The type VII remained the backbone of the fleet in 1943.