In 1941 Douglas Aircraft Company began work on their twin-engine medium-bomber A-26 Invader. By the end of production there were 2,452 aircraft produced for all variants. The A-26/B-26 was the only U.S. bomber to take part in three wars, WWII, Korea and Vietnam. The confusion with the use of the designation B-26 began when the Martin B-26 Marauder was retired and in 1948 the USAF dropped the “A” (Attack) designator so the Douglas A-26 Invader became the B-26 Invader. The A-26 made its first European appearance in late 1944.
The B-26K “Counter Invader” was a highly-modified twin-engine Douglas “A26 Invader”. The modifications included new engines, dual controls in cockpit, wingtip fuel tanks as well as new avionics. The turret armament was removed in favor of fixed forward-firing weapons. Eventually the engine cowlings were changed along adding 3-bladed reversible cropped propeller units. One the largest modifications was a new tail section. The USAF received the first of 30 B-26Ks in the Spring of 1964 with the last aircraft being delivered in April 1965.