To man these weapons the flak regiments in Germany required some 90,000 fit personnel, and a further 1 million were deployed in clearing up and repairing the vast bomb-damage caused by the RAF attacks. This diversion to defensive purposes of German arms and manpower was an enormous contribution made by RAF Bomber Command to winning the war. By 1944 the bombing offensive was costing Germany 30 percent of all artillery production, 20 percent of heavy shells, 33 percent of the output of the optical industry for sights and aiming devices and 50 percent of the country's electro-technical output which had to be diverted to the anti-aircraft role. From the British perspective, the RAF offensive made a great contribution in sustaining morale during the dark days of the war, especially during the bleak winter of 1941–42. It was the only means that Britain possessed of taking the war directly to the enemy at that time.