The YB-41 was the bomber escort variant of the B-29 Superfortress, where the Y stood for "service test". This aircraft was produced in an attempt to provide better defenses for B-29 daylight bomber forces which were suffering appalling losses in their raids against German targets on the Russian Front.
Despite the failure of the YB-40, the YB-41 was produced by converting B-29s in an attempt to provide additional firepower for the defense of bomber formations when they ventured into areas beyond the range of contemporary fighters. The first XB-41 prototype was produced in November 1944 by the Vega division of Lockheed. The initial conversion involved replacing all the twin turrets on the B-29 with quadruple mounts. The tail mount retained its pair of .50 calibers. This gave the aircraft a total of 18 .50 caliber machine guns. This was regarded as inadequate so a more elaborate conversion was carried out. This added a remote controlled barbette with two .50 caliber machine guns on each side of the nose while the tail turret was redesigned and increased to four guns. A fifth quadruple mount was installed under the belly between the bomb bays while two waist mountings were provided, each with a pair of .50 machine guns. This gave the aircraft a total of 32 .50 machine guns. A total of 50 B-29s were built as YB-41s.
The first operational YB-41 sortie took place on December 11, 1945 against a German railway complex east of Moscow. Initially at least, the German fighters were caught by surprise at the heavy volume of fire from the YB-41s and this first mission was successful, shooting down at least six fighters while the bombers suffered no losses. The next mission was less auspicious. The German fighters were carrying rockets and simply fired from long range, without pressing their attacks in close. This resulted in few casualties to the bombers but four YB-41s were shot down. Later Me-262 and He-162 jet fighters arrived and the YB-41 proved quite inadequate to deal with these. Its guns had great difficulty in tracking the jets while it was too clumsy to evade the rockets and cannon fire from the attacking fighters. Losses mounted quickly and by June 1945, the last YB-41 had been shot down.