Douglas A-26 Invader
Douglas A-26 Invader, the last aircraft designated as an “attack bomber,” was designed to replace the Douglas A-20 Havoc/Boston. It incorporated many improvements over the earlier Douglas designs. The first three XA-26 prototypes first flew in July 1942, and each was configured differently: Number One as a daylight bomber with a glass nose, Number Two as a gun-laden night-fighter, and Number Three as a ground-attack platform, with a 75-millimeter cannon in the nose. This final variant, eventually called the A-26B, was chosen for production.
Upon its delivery to the 9th Air Force in Europe in November 1944 (and the Pacific Theater shortly thereafter), the Douglas A-26 became the fastest US bomber of WWII. The A-26C, with slightly-modified armament, was introduced in 1945. The Douglas A-26 Invader combat career was cut short by the end of the war, and because no other use could be found for them, many A-26 Invaders were converted to JD-1 target tugs for the US Navy.
A strange aircraft-designation swap occurred in 1948, when the Martin B-26 Marauder was deactivated and the Douglas A-26 Invader was re-designated the B-26. (It kept this designation until 1962.) B-26 Invaders went on to serve extensively in both the Korean and Vietnam wars.
In Vietnam, they were commonly used in the Counter-Insurgency (COIN) role, with very heavy armament and extra power. This version, the B-26K, was based in Thailand and was, to confuse things further, called the A-26 for political reasons. B-26s were also used for training, VIP transport, cargo, night reconnaissance, missile guidance and tracking, and as drone-control platforms.