sheets of fire in the path of low flying fighters. As a result of these measures Allied fighter losses increased. The introduction of the B-17G with its remote controlled 'chin' turret forced a change of tactic on the Jagdwaffe. Throughout 1943 head-on attacks had proved successful against American heavy bombers. Many Luftwaffe units now upgraded the firepower of their fighters. Some Fw 190 fighters carried MK 108 30 mm cannon that could destroy most heavy bombers with two or three hits. The later variants of the Messerschmitt Bf 109 (from the Gustav onwards) were also capable of carrying heavier armament like the MK 108, although only a single barrel firing through the propeller shaft as an engine-mounted Motorkanone. By September 1944 the Soviets were advancing into Romania and the oilfields were lost. From this time, the Luftwaffe experienced chronic shortages of fuel. Many German interceptors returning from missions switched off their engines on touching down to avoid wasting fuel. Ground crews then quickly got them under cover. By this time fighter pilot losses were becoming unbearable, and the Jagdwaffe was nearing breaking point. The end in the West 1944–45 Between January and May 1944 the Luftwaffe undertook Operation Steinbock, the so-called Baby Blitz, assembling 474 bombers for a campaign against London. Steinbock was called off when V-1 flying bombs became available for the retribution attacks and after the loss of 329 bombers. The lack of night flying experience of the crew contributed to the losses. The bomber force, under the command of Oberst Dietrich Peltz, now had only 143 bombers available for the Normandy invasion. By 1944 the Luftwaffe was no longer in a position to offer serious opposition to Operation Overlord, the Allied invasion of France on 6 June 1944. Only a handful of Luftwaffe operations were launched against the beachheads. The most well known was the action to occur over the beaches was a strafing run conducted by the Fw 190 ace Josef Priller and his wingman, Emil Lang scored 29 victories against the Western Allies, all but one over the Normandy invasion front, making him the highest-scoring German ace of the campaign. During Operation Market Garden, the Allied attempt to end the war in 1944 by forcing a route through the Netherlands and into the Ruhr region of Germany, Luftwaffe fighter forces managed to inflict significant losses on Allied planes transporting paratroopers and supplies into battle, but