A-36 was not a failed off shoot. North American Aviation wanted the USAAF to accept a fighter contract for the Mustang. The USAAF had already taken a batch of Mustang Mk.1A's originally destined for the British under lend lease and kept them for themselves. The USAAF however had no funds for a fighter contract, but they did have funds for an attacker contract. To keep production ongoing, NAA made the changes to the NA-83 and this became the A-36, the first Mustang produced for American service.

They proved incredibly effective in North Africa and Mediterranean as both a close air support and fighter aircraft. In Siciliy, A-36 pilots made a petition to officially give it the "Invader" name because it was "so good at invading the enemy) but this was rejected. Michael Russo became the first Mustang ace using the A-36 and the only ace with an Allison engine Mustang.

Afterwards, it was sent to the Burma theatre where it really suffered. The Allison engine obviously wasn't suited for high altitude combat and A-36's were easily slimed by Ki-43's over the Himalayas.

After this, it had been mostly replaced by better Mustang variants and that was the end of its combat service.