Officially designated as the Medium Tank, M3 was the first US medium tank to be mass-produced. It was conceived and designed around 1940 and became operational in 1941. Its turret was made in two variants, one according to US specifications and the other modified to meet British requirements, in this case including the placement of the radio next to the commander. In the context of the British Commonwealth, the tank acquired two distinct designations: those with US-model turrets were called 'Lee', in homage to Confederate General Robert E. Lee, while those with British-model turrets were identified as 'Grant', in honor of Union General Ulysses S. Grant, the two greatest and most famous American generals of the Civil War.