Section Leaders:
Fionn Kelly & Madmatt

Early Development of US Medium Tanks

By Dan “dano6” Kowaleski

Introduction:

During the post World War I era, the US found that its tank force was completely unprepared to fight any kind of armored conflict. The development of a new medium tank that would be effective during World War II was very slow and inefficient. It would take almost 20 years to develop a medium tank that would be mass-produced. Many designs were built and tested, but very few medium tanks were ever actually deployed by an armored division. Most of the designs were extremely poor and ineffective as seen by the photographs and descriptions in the article below. The M2-M3 light tank became the tank of choice for the US armored forces up until the introduction of the M3 medium tank. The M2 and M3 light tanks, during WWII, were shown to be completely ineffective in almost any type of role except that of reconnaissance. Could you imagine what would have happened if the development process of the US medium tank had resulted in failure and the M2-M3 light tank series became the United States’ main line battle tank. Well, this inconceivable blunder was not to be the case. The United States’ extremely ineffective tank development program eventually led to the development of the M4 Sherman medium tank. The article below shows the various stages that led to the development of the M3 medium tank. The M3, “Grant” or “Lee” as it was called, is the direct predecessor of the M4 Sherman.

Development Process:

Upon the conclusion of World War I, US tank units were typically equipped with the leftover armor from that conflict. The United States had a limited amount of tanks consisting of the 6-ton, light tank, patterned after the French light tank, the Renault FT-17 and the Mark VIII British heavy tank. Both these tanks were equally outdated and obsolete by 1919.

From left to right: the Ford 3-ton, the 6-ton M1917, and the 40 ton Mark VIII. These were the only operational tanks in the US Army until the 1930's.

Both the US, and British determined that development of new light and medium tanks with greater mobility would be required.  In June 1919, the US Ordnance Department issued an order for the development of a new medium tank with a weight limit of 17 tons and a required weight to horsepower ratio of 10:1. The new tank would be designated the M1921. The M1921 would be designed with armor thickness equivalent to prevent penetration from anti-tank rifles and close range .50 caliber rounds. The M1921 and M1922 prototypes would be armed with the 6 pounder, anti-tank gun, fitted in a full 360-degree rotational turret with a .30 caliber machine gun mounted coaxially. Another .30 caliber mg was placed in the commander’s copula.

The M1921 and M1922, both proved to be under-powered and unreliable when tested at the Aberdeen Proving Grounds. Neither tank, equipped with the Murray-Tegurtha motor, could reach the speeds desired by the US Army. Different motor combinations were tried with limited success and further unreliability. In 1924, the US Ordnance Department decided that a special tank engine needed to be developed in order to increase reliability of the new medium tank. The Packard Motor Company was contracted with the design and manufacture of the new motor. The new motor was completed in June 1925 and was installed in the M1921.  The new motor proved to be much more reliable, but was still under-powered. Both the M1921 and M1922 remained in service as test beds for various experimental components for many years.

The Medium tank T1 before refitting of 75mm pack howitzer. This tank is almost identical to the M1921 except for minor differences.

The medium tank T1 was almost identical to the M1921 and M1922 models except that the 57mm gun was removed and a 75mm-pack howitzer, M1920, was installed in the turret. The 75mm gun proved very deadly against light tanks. Only one T1 was every built and it also served as a test vehicle for many different components including the 75mm howitzer.

At the same time the M1921 and M1922 tanks were being built, Mr. J. Walter Christie was undertaking an alternate design for the medium tank. During World War I, the major mechanical failure of tanks was due to the track suspension system and the tracks themselves. Many of these breakdowns occurred on the way to the battlefield before the tank actually saw any combat. Christie’s designs utilized convertible tracks on the new tank. The convertible track allowed the use of the road wheels without the tracks for on-highway use, thus eliminating the failure of the tracks in movement to the battlefield. The first tank of this design was the M1919.

The M1919 weighed in at 27,000 lbs. and carried the same armament as the M1921. It had a 57mm gun mounted coaxially with a .30 caliber machine gun in a full traverse turret. It also had the .30 mg in the commander’s cupola. The tank was tested at Aberdeen, with a top speed of 13 mph on wheels and 7 mph on tracks. Christie applied for a modification request and it was granted. The M1919 was modified with the removal of the turret and the addition of the main gun to the front of the chassis. Machine guns were also mounted to the front of the chassis. This design proved to be too cramped and unreliable. The M1919 was consigned to the vehicle museum at Aberdeen in June 1924. (insert picture of modified M1919)

Upon the rejection of the M1919 and the M1921, Christie turned his designs towards a high-speed light tank chassis. This chassis would later turn out to change tank design around the world.

Christie's T3 shown here with the single pin tracks.

The design looks a lot like the suspension of the Soviet BT-5 and the T-34 but that is another story. Christie’s new tank was called the M1928 and was capable of speeds up to 70 mph on the road wheels without tracks. The US Army took notice and contracted Christie to build one of the tanks for them. It was designated the M1931. After tests and modifications Christie was contracted to build 7 of the M1931 which was designated convertible tank T3. The T3 was armed with a 37mm gun mounted coaxially with a .30 caliber M1916 machine gun in a full 360-degree rotational turret.

All of the T3s were delivered by March 1932. They were assigned to 67^th infantry division and to the Calvary at Fort Knox. The highly sloped armor was 5/8-1/2 inch thick. The US Army had disputes with Christie as to the light armament and also the thin armor. The ordnance department designed an improved version of the T3, and a contract was issued for five additional improved versions of the T3. This contract was not given to Christie but to the Foamite Corporation. The improved version of the T3 was designated the convertible tank T3E2. The new tank was wider in order to fit a gunner next to the driver to operate the new .30 caliber bow machine gun. The turret was also enlarged to hold three new .30 caliber machine guns, one in the back of the turret and two on the sides.

A new, more powerful engine was also fitted into the T3E2, which raised its horsepower from 338 hp to 435 hp. The max speed of the T3E2 increased to 35 mph with tracks. The higher horsepower engine also caused many breakdowns and resulted in the redesign of over 60 different parts. All five of the T3E2 were refitted with the redesigned parts and designated the convertible tank T3E3.

The last tank to be built using Christie’s convertible track design was the T4. Sixteen of the T4s were built during 1935-1936. These tanks were armed with a .30 caliber bow machine gun, and two machine guns in the turret, a .50 caliber mg and a .30 caliber mg. The T4 and T4E1 were both determined to be under-powered during testing. Both tanks were declined for standardization because of the lack of offensive firepower and high cost. The T4 was twice the cost of the M2 light tank and had less firepower than the M2.

Christie's medium tank T4.

The US Ordnance Committee recommended on May 21, 1936, that a new medium tank be developed. This new tank would eventually become the M4 Sherman. The new tank would be built to pass the Infantry Boards requirements, none of the previous designs, as shown above, had met these standards. The new tank was designated the T5 and its design would be based upon the M2 light tank. The design of the T5 used many of the components from the M2 light tank, but the T5 would have more firepower and armor than the M2.

The armament of the T5 was a 37mm high velocity gun in a 360 degree full traverse turret along with 4 .30 caliber machine guns in sponsons at all four corners. The Phase 1 development of the T5 saw the elimination of the 2 front mg sponsons and the mounting of 2 static .30 caliber machine guns in the front hull.

The medium tank T5. This tank would go on to become the M3 Grant/Lee with some major revisions. Notice that the suspension is the same as the M3/M4 series of medium tanks.

The phase 1, T5 was standardized the medium tank M2 in 1938. Phase 3 developments of the T5 included additional armor and more powerful motor, but the Phase 3 basically remained the same as the phase 1 tank. In 1939, a 75mm M1A1 howitzer was fitted into a T5 phase 3 tank to test the effectiveness of a larger caliber main weapon in the T5 chassis. The 75mm howitzer proved itself very effective against all types of targets. This new tank was designated the T5E2.

The T5E2 with a 75mm howitzer mounted in the front hull.

The newly standardized M2 was produced and sent to the armor divisions in the US. A total of 18 M2s were delivered to the US tank force by early 1940. Then the blitzkrieg of Poland and the sudden collapse of France to the Germans alarmed the US considerably and the mass production of tanks became a major concern. It was determined that the Rock Island Arsenal was far too limited to produce a significant number of tanks in order to rearm the US tank force. Chrysler and other manufacturers were contacted to deduce their ability and willingness to build tanks for the US Army. Chrysler agreed to build tanks and received a contract on August 15, 1940 to build 1,000 M2A1 medium tanks for the US Army.  Battlefield intelligence from the European theatre showed that the Germans were using a 75mm gun in the Mark IV medium tank. This new development made the 37mm main armament on the M2A1 obsolete. A new tank was designed that was based upon the M2A1. This new tank design was for the M3 medium tank and Chrysler’s contract was changed to produce 1,000 of the new M3s. The existing M2A1 tanks that had already been built were used for training exercises in the US. The M3 medium tank would be the first US designed medium tank to see combat in World War II.

References:

Hunnicutt, R.P., “Sherman: A History of the American Medium Tank”. Presidio Press, Novato, CA 1994.