Sure they were. The Dot, later changed to Dat, was started in 1923. But during the war years, all the car makers were producing military vehicles, particularly Datsun. They were rolling out jeeps, trucks, artillery trailers, you name it. The allies bombed the crap out of the Japanese car company factories. And after the war, the U.S. helped them get back in production again in order to rebuild Japan (to help us fight the communists in Asia). Mitsubishi was more tied into aircraft and ship building, but Datsun made land vehicles.
I think the DATs go back to the teens.