Medium Tank M3, Fort Knox, June 1942. The Medium Tank M3 was an American tank used during World War II. In Britain the tank was called by two names based on the turret configuration. 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 U.S. General Ulysses S. Grant. Design commenced in July 1940 and the first M3s were operational in late 1941. The U.S. Army needed a good tank and coupled with the United Kingdom's demand for 3,650 medium tanks immediately, the Lee began production by late 1940. The design was a compromise meant to produce a tank as soon as possible. The M3 had considerable firepower as it was well armed and provided good protection, but had certain serious drawbacks in its general design and shape, such as: a high silhouette, an archaic sponson mounting of the main gun, riveted construction, and poor off-road performan...