Authored By Dan Alex (Updated: 5/3/2016):
The M3 Stuart was made possible by work conducted during the post-World War 1 years. This culminated in development of small, active combat systems for use in infantry support actions using a tracked chassis with machine gun armament. This gave rise to the "M1 Combat Car" which was then followed into service by the cannon-armed M2. Both designs appeared during the 1930s. It was only the rapid expansion of German ground forces in their takeover of Europe during 1939-1940 that serious thought was given to a successor for the M2 as it now proved an obsolete machine. This work then begat the M3 which promised improved protection (at the expense of speed) and greater armor protection. A new suspension arrangement rounded out the list of sought-after qualities.
After a period of testing and evaluation, the U.S. Army adopted the "Light Tank, M3". When accepted by the desperate British Army under Lend-Lease, they assigned it the name of "Stuart" after the American Civil War Confederate General J.E.B. Stuart. In this way the M3 Medium Tank became the "Lee" (General Robert E. Lee) or "Grant" (General Ulysses S. Grant) and the classic M4 Medium Tank was the "Sherman" (General William Tecumseh Sherman). American Car and Foundry was charged with production of the M3 Light Tank and this began in earnest during March of 1941.
By this time, Europe had mostly fallen under the might of the Axis forces as Britain attempted to stave off complete elimination across its vast empirical holdings. Lend-Lease allowed American support of its overseas ally by delivering war-making goods without officially having declared war on any one enemy. As such, first combat use of Stuarts occurred with the British in November of 1941 during Operation Crusader. From these actions, the M3 was found to possess a rather weak main gun but its reliability in desert conditions was noted as was maneuverability. The Americans did not press their M3s into combat until the Philippines campaign of 1942.
The M3 was powered by the Continental W-670-9A, a gasoline-fueled, air-cooled radial aero engine of 7-cylinders and outputting 250 horsepower. This powerpack resided in a rear compartment away from the crew. Suspension came from the Vertical Volute Spring Suspension (VVSS) system which, coupled to the hull design and engine fitting, allowed the vehicle a top speed of 18 miles on road and operational ranges out to 75 miles. Its crew of four was made up of the driver, commander, gunner and bow machine gunner/radio operator. Conditions were decidedly cramped considering internal volume was also taken up by necessary equipment and ammunition stocks. Armament centered around the 37mm M5 (later M6) main gun with coaxial 0.30 caliber M1919A4 Browning machine gun. Four additional 0.30 caliber machine guns were installed including one over the turret, one in the right front of the hull (ball mounting) and the remaining pair in individual side sponsons along the forward superstructure panel. The main gun sat atop a unique mounting in which the gun could traverse some 20-degrees to either side apart from the turret - this gave the gunner some flexibility without needing the entire turret to be turned. The turret was set over midships with the driver seated front-left the hull, the bow gunner to his right and the remaining two crew in/under the turret. The hull crew used hinged vision slots for situational awareness though their forward panel was nearly vertical - shot trap for enemy fire. The track-over-wheel arrangement saw four road wheels used with a front drive sprocket and rear track idler. Overall, the M3 was a classic light tank design of the period, utilizing many established design features seen in competing designs elsewhere.