The M3 medium tank was developed and manufactured in the United States during World War II. When the German Army's western blitzkrieg started in May 1940, the U.S. Army decided that the 37mm tank gun equipped with the M2A1 medium tank it owned was not powerful enough, and hurriedly installed a new model equipped with a 75mm tank gun. At that time, the United States had no experience in developing a tank with a 75mm cannon mounted on a rotating turret, so it was decided in June 1940 to develop a medium tank equipped with a 75mm cannon on the front right side of the hull.
As a result, the M3 medium tank has an M2 75mm cannon on the right side of the hull, a small all-around turret equipped with a 37mm secondary gun on the top of the fighting compartment, and a 7.62mm machine gun on top. It was completed as an irregularly shaped tank with a long cupola attached. The M3A4 is a type that replaces the A57 double-row liquid-cooled gasoline engine with five in-line 6-cylinder gasoline that was produced for buses and connected in a star shape. All 109 of these tanks produced were operated for training in the U.S. In Britain, the tank was called by two names based on the turret configuration and crew size. Tanks employing US-pattern turrets were called the "Lee", named after Confederate general Robert E. Lee. Variants using British pattern turrets were known as "Grant," named after Union general Ulysses S. Grant.