M2 Medium Tank

The Medium Tank M2 was a United States Army tank that was first produced in 1939 by the Rock Island Arsenal, just prior to the commencement of the war in Europe. Production was 18 M2 tanks, and 94 slightly improved M2A1 tanks, for a total figure of 112. Events in Western Europe and on the Eastern Front rapidly demonstrated that the M2 was obsolete, and it was never used overseas in combat; it was used for training purposes throughout the war.

The M2's unique features included an unusually large number of machine guns, bullet deflector plates, and sloped armor on the hull front (glacis plate). The main armament was a 37 mm gun, with 32 mm armor; the M2A1 had a 51 mm gun mantlet. The features of the M2 series development, both good and bad, provided many lessons for U.S. tank designers that were later applied with great success in the M3 Lee, M4 Sherman and many other armored fighting vehicles.

Design
Rock Island Arsenal started work on a new medium tank, based on the design of the M2 Light Tank. Initially designated the T5, the redesigned model (with a 350 hp R-975 radial engine) was redesignated as the M2 Medium Tank in June, 1939. After the first 18 units had been produced at Rock Island Arsenal and evaluated by the army, the upgraded M2A1 specification was approved with a redesigned turret and a more powerful engine.

The medium tank M2 was a larger development of the M2 Light Tank. Many components were common or used a similar design, including the vertical volute spring suspension which would be used in later tanks as well. Twin-wheeled bogies were mounted externally, and rubber-bushed and rubber-shoed track proved durable on roads. The initial M2 model was powered by an aircooled Wright R-975 radial engine. For the M2A1, this engine was supercharged to provide an extra 50 hp for a total of 400 hp, and designated as the R-975 C1 radial engine.

The M2 had a high superstructure, with a sponson-mounted machine gun in each corner. In addition, two more machine guns were fixed in the glacis plate and fired by the driver. Surmounting the superstructure was a small revolving turret armed with a 37 mm Gun M3 and a coaxial machine gun. The 37 mm gun could penetrate 46 mm of face-hardened armor sloped 30° at a range of 500 yards (457 meters), and 40 mm at 1,000 yards (914 meters). This armament configuration was a hybrid between the sponson-mounted weapons of the Mark VIII Liberty tank of World War I vintage, and the combination of turreted cannon, coaxial machine gun and glacis-mounted machine gun that was almost universal in World War II medium tanks. (Two additional .30-caliber machine guns could be mounted on pintles on either side of the turret for anti-aircraft use, bringing the total to nine—surely a record for any tank brought into service by any army.) The crew consisted of the tank commander, a driver and four gunners. The vehicle provided internal stowage for 200 rounds of 37 mm ammunition and up to 12,250 rounds of .30-caliber.

Bullet deflector plates were installed over the rear fenders. The idea behind these plates was that the tank could drive over a trench, and the rear sponson machine guns could then fire onto the plates; the bullets would deflect into the trench or the area directly behind the tank. Like the sponson machine guns themselves, the deflector plates turned out to be useless in modern warfare.

Production
Chrysler opened a new tank plant, the Detroit Arsenal Tank Plant, to manufacture the M2, and the US Government contracted in August, 1940 for 1,000 vehicles to be produced. Events in Europe made obvious that the M2 was obsolete, and the government modified the contract before production began. Instead of M2 medium tanks, the plant would now build 1,000 M3 Grant tanks. Production of the M2 was returned to the Rock Island Arsenal, where 94 M2A1s were eventually built. The M2A1 had slightly better armor and a slightly larger turret than the original M2, since it had the turret from the M3 Light Tank, with gun mantlet armor 2 inches (51 mm) thick.

Service
The M2 was already obsolete when it entered service. It compared poorly with contemporary European tanks, such as the French S-35, German Panzer III and Soviet BT-7, which were somewhat better protected against 37 mm hits. The 37 mm main armament of the M2 was equivalent to the 37 mm the Panzer III, but the 45 mm BT-7 and 47 mm S-35 had more powerful guns. By 1941, Germany had upgunned the Panzer III with a 50 mm L/42 gun, and the Soviets had fielded the vastly superior T-34, with a 76 mm gun and a sloped 52 mm glacis plate. Given this, the M2 was essentially a stopgap measure until more capable tanks like the M3 Lee and M4 Sherman came along in 1942-43. Although 18 M2s and 94 M2A1s were produced, the Ordnance office recommended in January 1942 that they should only be used for training purposes, and they were never sent overseas to combat areas. The U.S. Army fielded the M2 and M2A1 with the 67th Infantry Regiment (Medium Tanks) and, subsequently, the 1st Armored Division's 69th Armored Regiment during intensive training maneuvers in the United States in 1941, and the M2 design continued to prove useful in a basic training role for tank crewmen. The trained crewmen from the 69th Armored were scattered to provide cadres to several new armored divisions and independent M4 tank battalions, as U.S. armored forces were rapidly expanded in 1942-44.



For combat the M2 was generally a poor design, with thin armor, inadequate main armament and a high profile. The four sponson-mounted machine guns proved to be completely unnecessary and ineffective. But the design provided a few important lessons that were used for the later M3 and M4 medium tanks. In particular, the M2's sloped frontal hull (glacis plate) was extremely advanced for a 1939 design — the one bright spot in an otherwise dismal design — and a sloped glacis plate with substantially heavier armor would become a permanent feature of U.S. tank design. The next medium tank would have to match the German Panzer IV's 75 mm turret gun. Since no suitable turret had been designed in the US, the Lee was designed first to mount a 75 mm gun in the right sponson, which had been tested on an M2; the experimental vehicle was designated T5E2. The Lee's gun was mounted in a conventional turret on a modified M3, to produce the first Sherman eight months after the first Lee.