M2 light tank

The Light Tank M2 was an American pre-World War II light tank equipped with one 37 mm M5 gun, one .50 M2 Browning machine gun, and five .30 cal M1919 Browning machine guns, which saw combat with the US Marine Corps 1st Tank Battalion on Guadalcanal in 1942, during World War II. It was developed originally from the T2 pilot tank made by Rock Island Arsenal, which had leaf spring suspension and evolved into the T2E1 pilot tank. The T2E1 became standardized in 1935 by Rock Island Arsenal. After the Spanish Civil War, machine guns were not used on M2 light tanks because they were proven weak in the war, which made the M2A4. Instead of the machine guns, they had a 37 mm gun as the main armament. The successor vehicles to the M2 light tank, the M3 Stuart, M2 Medium Tank, and the M4 High Speed Tractor.

Its service with the 1st Tank Battalion during the Pacific War was its only U.S. combat use during the war; however, it is believed that M2A4s served in Burma and India with the British 7th Hussars and 2nd Royal Tank Regiment during their engagements with the Imperial Japanese Army's 14th Tank Regiment. The M2A4 was the immediate predecessor of the M3 Stuart series of light tanks which saw widespread use throughout the war, and the M2 Medium Tank, an unsuccessful design that led to the M3 Lee and M4 Sherman medium tanks.

Specifications
The M2A4 was 14 ft long, 8 ft wide, 8 ft high, and weighed 11.6 t. It had a vertical volute spring suspension and had a speed of 36 mph, and had a range of 320 mi. It had one M5 37 mm gun, two .50 cal M2 Browning guns and five .30 cal M1919 machine guns with 6 to 25 mm of armor. It had an 250 hp Continental W-670 9A seven-cylinder radial engine. The vehicle was operated by a crew of four.

M2A4's design
Besides the machine gun mounted coaxially to the main gun, there were three .30 cal .MGs on the front hull of the M2. One was mounted in a ball mount in front of the bow gunner. The other two were mounted in the upper hull near the sides of the tank. The machine guns were operated by the driver with the triggers on his to his steering laterals. Troops could also mount another .30 cal machine gun on the top of the turret for anti-aircraft defense.

Shooting procedure
The 37 mm M5 gun was operated by the Tank commander with a manually operated breechblock. The commander doubled as loader, like many other tanks of the time, who stood on the right side, while the gunner stood on the left side. There was no turret basket in the M2A4 light tank.

First, the commander had to turn the turret in the general direction of the target. The gunner would locate the target using a M5 telescopic sight, then he would use a shoulder rest attached to the main gun's breech ring to fine tune his aim. This was made possible with the 20° of traverse built into the M20 combination mount, which was accomplished with rack and pinion traverse gear. The depression and elevation was also done manually done by the gunner.

Development history


The pilot T2 light tank was built and designed by the Rock Island Arsenal in 1933. It had a simple box-like hull with rear-mounted engine and drive to the front sprockets. These features were inherited from the later T1 series experimental tanks, but the suspension was copied from the Vickers 6-ton tank which had been demonstrated in America. Comparative trials with the contemporary T5 Combat Car showed, however, that the vertical volute spring suspension of that vehicle was much superior to the Vickers leaf spring suspension. Vertical volute springs were fitted in a second prototype, the T2E1, produced after the trial in April 1934. The armament of the T2E1 was one .30 cal and one .50 inch (12.7 mm) Browning machine guns mounted in a single fixed turret nearly the whole width of the hull, with another .30 cal Browning mounted on the hull front.

As the Light Tank T2E1, the M2 was developed in 1935 by Rock Island Arsenal for the Infantry Branch of the U.S. Army. The design coming from the earlier T1 and T2 was somewhat inspired by the British Vickers 6-ton tank which was widely exported. Its main weapon was a single 0.5 cal (12.7 mm) M2 Browning heavy machine gun installed in a small one-man turret. After only 10 units were delivered, the Infantry branch decided to switch to a twin turret configuration, with a .30-caliber (7.62 mm) machine gun in the second turret. These early twin-turret tanks were given the nickname "Mae West" by the troops, after the popular busty movie star. The twin-turret layout was inefficient, but was a common feature of 1930s light tanks derived from the Vickers, such as the Soviet T-26 and Polish 7TP. Further refinements to the M2A2 produced the A3 model, which incorporated a modified suspension system that reduced the tank's ground pressure. The weight increased to 10 tons.

Following the Spanish Civil War, most armies, including the U.S. Army, realized that they needed tanks armed with cannon and not merely with machine guns. The Cavalry branch had already opted for a single, larger turret on its nearly identical M1 Combat Car. In December 1938, OCM #14844 directed that a single M2A3 be removed from the assembly line and modified with heavier armor and weapons, to meet the standards of the U.S. Infantry. This vehicle, after conversion, was re-designated as the M2A4. It was equipped with an M5 37 mm main gun, 1 inch (25 mm) thick armor, and a seven-cylinder gasoline engine. Other upgrades included improved suspension, improved transmission, and better engine cooling. Production of the M2A4 began in May 1940 at the American Car and Foundry Company, and continued through March 1941; an additional ten M2A4s were assembled in April 1942, for a total production run of 375 M2A4 light tanks. The US Army sent out press photos still showing the M2A4 being assembled in July 1941 after the assembly line had been changed over to the M3.

Successor vehicles
The M2 Light Tank's importance lies in the sound basis it provided for US M3-series and M5-series light tanks, and M3-series and M4-series medium tanks in World War II. The high speed, mobility and mechanical reliability of all these tank designs were legacies of the M2 Light Tank program. The Ordnance Department viewed the M2A4 as a stopgap tank; work to improve it further began in June 1940. The first M3 Stuart tanks began to be produced in March 1941; the original riveted M3s closely resembled the M2A4, and the two types occasionally served in the same units; the easiest recognition feature is the aft (rear) idler wheel. On the M2A4, the idler is raised; on the M3 it trails on the ground, increasing the flotation of the heavier vehicle. The M3 retained the same Continental W-670 engine, but incorporated ½-inch thicker (1½ inch total thickness) armor; weight increased to 14 tons. The tank kept the same 37 mm gun, but the turret incorporated numerous improvements. Over 4,500 examples of the initial model were produced.

Rock Island Arsenal also developed the M2 Medium Tank from the M2 Light Tank design. The M2 was an unsuccessful design, and was kept in the U.S. and limited to training use, but it served as the predecessor for the M3 Lee and M4 Sherman, which were successful and many other armored vehicles were based on the M3 and M4 chassis. The M4 Tractor was developed from the running gear of the M2, and used extensively from 1943 onward.

Employment
By December 1941, the M2A1, M2A2 and M2A3 were used for training only. The majority of M2A4s, which went to the US Army, were also used only for training between 1940 and 1942. The U.S. Marine Corps ordered M3 Stuart tanks to outfit its armored units in 1940, but as the new tank was not yet in production, it received 36 M2A4s, after which point production of the M3 had come on line. Many of these tanks were deployed during the Battle of Guadalcanal while assigned to the A Company, 1st Tank Battalion, where they and M3 Stuarts were typically spread out among infantry units. Their use was generally limited to providing mobile fire support to the Marines, either in disabling Japanese bunkers or using canister shot against Japanese attacks. In defensive engagements, the M2A4s and Stuarts would deploy in pairs, so they could cover each other with machine gun fire against Japanese soldiers armed with satchel charges.

Ultimately, the Marine Corps determined that the 37 mm gun of the M2s and M3s was not powerful enough to defeat Japanese bunkers, and so they would be replaced with tanks armed with 75 mm guns. Following the end of the Guadalcanal campaign, A Company returned to Australia, where the M2A4s were replaced with the new M4 Shermans in preparation for the Battle of Cape Gloucester in December 1943. They remained in service in some areas of the Pacific Theater until 1943. After they served in the Pacific, they were used for training.

Britain ordered 100 M2A4s in early 1941. After 36 of them were delivered, the order was canceled in favor of an improved M3 Stuart. The fate of these vehicles is unclear. There is evidence that indicates those 36 M2A4s were shipped off from North Africa as part of the British Army's 7th Hussars and 2nd Royal Tank Regiment, fighting in the India and Burma campaigns against the Japanese 14th Tank Regiment. However, according to historian Mike Green, the tanks were never issued to combat units.

Variants

 * M2A1 (1935).
 * Initial production type with single fixed turret containing one .50 cal MG. 17 units were produced.
 * M2A2 (1935).
 * Twin turrets with two .50 MGs. Dubbed "Mae West". 239 units produced. Had a 270 degree range of fire, since the turrets partly fouled each other.
 * M2A3 (1938).
 * Twin turrets with two MGs, Thicker armor, slightly lengthened hull, improved engine access, increased gear ratios, better engine cooling, improved suspension, and other minor detail changes. 72 units produced.
 * M2A4 (1939).
 * Single turret with 37mm gun. Thicker armor. 375 units produced. Orders went to the American Car & Foundry in October 1939 upon request by the Ordnance Department. Used in the early Pacific campaigns and training. Famously used in Guadalcanal. Used for training after December 1941.