The American M3 medium tank was a famous tank in the early part of World War II. The total production volume of the M3 medium tank series reached 6,258 units, and it has many unique features and occupies a certain position in the history of world tank development. The full name of the M3 medium tank is the M3 "Grant"/"Lee" medium tank. In 1940, someone suggested improving the M2 medium tank, thickening the armor, and installing a 75mm howitzer in a protruding mount on the side of the body. This new tank was named the M3 medium tank by the U.S. Ordnance Commission on July 11, 1940. Due to the needs of the war, the M3 medium tank was approved for production soon after the design was completed. Crisler Company, Rolling Stock Company, and Baldwin Rolling Stock Factory in the United States all produced experimental prototypes in April 1941. Formal production began in August 1941 and ended in December 1942. In more than a year, a total of more than 6,000 M3 medium tanks were produced. Although they are both M3 medium tanks, the "Grant" tank and the "Lee" tank are slightly different. Equipped with a British-designed turret, it was named "Grant" Type I. The standard M3 medium tank is called the "Lee" I. The M3A1 is called the "Lee" II, the M3A3 is called the "Lee" IV, the M3A3 equipped with a diesel engine is called the "Lee" V, the M3A4 is called the "Lee" VI, and the M3A5 is called the "Grant" II.