The Medium Tank M3 was an American medium tank used during World War II. In Britain the tank was called "General Lee", named after Confederate General Robert E. Lee, and the modified version built with a new turret was called the "General Grant", named after U.S. General Ulysses S. Grant.
Design commenced in July 1940, and the first "Lees" were operational in late 1941. The U.S. Army needed a good tank and coupled with Great Britain's demand for 3,650 medium tanks immediately, the Lee began production by late 1940. The M3 was well armed and armored for the period, but due to design flaws (high silhouette, archaic sponson mounting of the main gun, below average off-road performance) it was not satisfactory and was withdrawn from front line duty as soon as the M4 Sherman became available in large numbers.
| Medium Tank M3 Lee | |
|---|---|
| Type | Medium Tank |
| Place of origin |  United States |
| Service history | |
| Used by |  Australia Brazil Canada New Zealand Soviet Union United Kingdom United States |
| Wars | World War II |
| Production history | |
| Produced | August 1941–December 1942 |
| Number built | 6,258 |
| Variants | numerous, see text |
| Specifications | |
| Weight | 30 short tons (27 t) |
| Length | 18 ft 6 in (5.64 m) |
| Width | 8 ft 11 in (2.72 m) |
| Height | 10 ft 3 in (3.12 m) - Lee |
| Crew | 7 (Lee) or 6 (Grant) |
| | |
| Armor | 51 mm |
| Main armament | 1 × 75 mm Gun M2/M3 in hull 46 rounds 1 × 37mm Gun M5/M6 in turret 178 rounds |
| Secondary armament | 2-3–4 × .30-06 Browning M1919A4 machine guns 9,200 rounds |
| Engine | Wright (Continental) R975 EC2 400 hp (300 kW)/340 hp (250 kW) |
| Transmission | Synchromesh, 5 speeds forward, 1 reverse |
| Suspension | vertical volute spring |
| Ground clearance | 18 in (0.46 m) |
| Fuel capacity | 662 liters (175 US gallons) |
| Operational range | 193 km |
| Speed | 26 mph (42 km/h) (road) 16 mph (26 km/h) (off-road) |
| Steering system | Controlled differential |
In 1939, the U.S. Army possessed approximately 400 tanks, mostly M2 light tanks, with less than a hundred of the discontinued M2 medium tanks. The U.S. funded tank development poorly during the interwar years, and had no infrastructure for production, little experience in design, and poor doctrine to guide design efforts.
The M2 series medium tank was typical of AFVs many nations produced in 1939. When the U.S. entered the war, the M2 design was obsolete with a 37 mm gun, 32 mm frontal armor, machine gun main armament and a very high silhouette. The Panzer III and Panzer IV's success in the French campaign led the U.S. Army to immediately order a new medium tank armed with a 75 mm gun in a turret. This would be the M4 Sherman. However, until the Sherman was in production, an interim design with a 75 mm gun was urgently needed.
The M3 was the solution. The design was unusual because the main weapon — a larger caliber, low-velocity 75 mm gun — was in an offset sponson mounted in the hull with limited traverse. A small turret with a lighter, high-velocity 37 mm gun sat on the tall hull. A small cupola on top of the turret held a machine gun. The use of two main guns was seen on the French Char B, the Soviet T-35, and the Mark I version of the British Churchill tank. In each case, two weapons were mounted to give the tanks adequate capability in firing both anti-personnel high explosive ammunition and armor-piercing ammunition for anti-tank combat. The M3 differed slightly from this pattern having a main gun which could fire an armor-piercing projectile at a velocity high enough for efficiently piercing armor, as well as deliver a high-explosive shell that was large enough to be effective. Using a hull mounted gun, the M3 design was produced quicker than if a turret mount gun had been manufactured. It was understood that the M3 design was flawed, but Britain urgently needed tanks.
The M3 was tall and roomy: the power transmission ran through the crew compartment under the turret cage to the gearbox driving the front sprockets. Steering was by differential braking, with a turning circle of 37 ft (11 m). The vertical volute suspension units included a return roller made with self-contained and readily replaced units bolted to the chassis. The turret was power-traversed by a electro-hydraulic system — a electric motor providing the pressure for the hydraulic motor. This rotated the turret fully in 15 seconds. Control was from a spade grip on the gun. The same motor provided pressure for the gun stabilizing system.
The 75-mm was operated by a gunner and a loader. Sighting the 75-mm gun used a M1 periscope — with an integral telescope — on the top of the sponson. The periscope rotated with the gun. The sight was marked from zero to 3,000 yd (2,700 m) with vertical markings to aid deflection shooting at a moving target. The gunner laid the gun on target through geared handwheels for traverse and elevation.
The 37-mm was aimed through the M2 periscope, though this was mounted in the mantlet to the side of the gun. It also sighted the coaxial machine gun. Two range scales were provided: 0-1,500 yd (1,400 m) for the 37-mm and 0-1,000 yd (910 m) for the machine gun.
The British ordered the M3 when they were refused permission to have their tank designs (the Matilda infantry tank and Crusader cruiser tank) made by American factories. British experts had viewed the mock-up in 1940 and identified several flaws — the high profile, the hull mounted gun, radio in the hull, smooth tracks, the amount of armor with insufficient attention to splash-proofing the joints. The British agreed to order 1,250 M3, to be modified to their requirements - the order was subsequently increased with the expectation that when a superior tank was available it could replace part of the order. Contracts were arranged with three U.S. companies, but the total cost was approximately 240 million US dollars. This sum was all of the British funds in the US and it took the Lend-Lease act to solve the financial problems.
The prototype was completed in March 1941 and production models followed with the first British specification tanks in July. The British cast turret included a bustle at the back for the Wireless Set No. 19 radio. It had thicker armour than the U.S. one and removed the U.S. cupola for a simple hatch. Both U.S. and British tanks had thicker armor than first planned. The British design required one fewer crew member than the US version due to the radio in the turret. The U.S. eventually eliminated the full-time radio operator, assigning the task to the driver. The British realized that to meet their requirement for tanks both types would be needed.
The U.S. military utilized the "M" (Model) letter to designate nearly all of their equipment. When the British Army received their new M3 medium tanks from the US, confusion immediately set in, as the M3 medium tank and the M3 light tank were identically named. The British army began naming their American tanks, although the U.S. Army never used those terms until after the war. The M3 tanks with the new turret and radio setup received the name "General Grant", while the original M3s were called "General Lee", or more usually just "Grant" and "Lee". The M3 brought much-needed firepower to British forces in the African desert campaign.
The chassis and running gear of the M3 design was adapted by the Canadians for their Ram tank. The hull of the M3 was also used for self-propelled artillery and recovery vehicles.
