Tuesday, November 1, 2011

The M3 General Grant/ General Lee

 by Phil Gardocki
M3 Grant with reduced profile turret.
As photographed by the author.
Used with permission from the US Army Ordnance Museum.
The Grant/Lee tanks have been much vilified by history and gamers alike - there was much fault to point at. At 10 feet tall, it had a high profile, its main gun was not on a turret, its anti-tank gun was inadequate to deal with current armor, its riveted construction lead to rivets becoming shrapnel inside the hull wounding or killing the crew, taking out the engine, and even setting off the internal ammo. Adding to its risks, its gasoline powered engine could catch fire easily.
However, the M3 did meet the requirements set for it, and was producible with the factories of the day. Even as the M3 was rolling out of the factory, the "Sherman" was on the drawing board. But in 1941, the US Armor divisions could have the medium tank M3, or go to war with the light tank "Stuart", but the high casualty rates for light tanks noted in the France and North Africa made the M3 a necessity.

The reason for the high profile was due to the requirements of having a 7.5 cm gun, which was regarded as the minimum caliber for a tank. This size ordinance could carry sufficient explosive to destroy obstacles and act as short range artillery when supporting attacks. However, the current manufacturing ability of hull sizes available were too small to support a turret ring for a 7.5 cm gun, so the compromise was reached to having two guns. The main gun was a barbette mounted low velocity 7.5 cm which only had 34 degrees of traverse. To meet a requirement for fast reaction time, the antitank gun had to be on a motorized turret, so the high velocity 3.7 cm gun to use as an anti tank weapon was placed on top. This added another foot to the profile. Adding further to the profile was the commander’s cupola and machine gun.

The Grant’s 3.7cm gun could penetrate about 5.8 cm of armor at 500 yards compared to the German 3.7cm KwK 35/36 L/46.5 penetrating 3.7cm at the same distance. In 1940 the maximum armor on a German Panzer III H and Panzer IV’s models A-D was 3cm. The American High Command regarded this as good enough, as the theory of tank combat was in exploitation, not tank to tank combat.* And for the task raising hell in enemy rear areas, the M3, with its 4 machine guns, a 7.5cm, and a 3.7cm gun was a land battleship.

M3A1 Lee II with cast hull.
Used with permission from the US Army Ordnance Museum.

One of the construction challenges faced by the factories was how to fabricate the M3 hull. Neither America nor Canada had the equipment to cast hulls of sufficient size. Although plans were underway to build the casting capacity, later used on all M4 and subsequent tank construction, the Allies could not wait for the new capacity and needed tanks immediately. As a compromise, rivets were used to join the 5 cm armor plate together. This allowed the armor to be rapidly cast in sections and assembled on the production line. The rivets were in the M3A3 and M3A5 were welded into the plates to stop them from spalling – breaking off and ricocheting around the inside of the hull – when the armor took hits from high explosives or anti-tank rounds.
The gasoline engine was used in early versions of the M3 because gasoline engines had a higher power to weight ratio than diesel engines, allowing a smaller engine, and thus less armor to protect it, yielding less weight overall for the same combat abilities. While the use of gasoline engines in tanks have been criticized, it should be noted that Germany also fueled their tanks with gasoline. The Soviet Union, after receiving after action reports on the Spanish Civil war of the flammability of tanks decided to make their own tanks run on diesel. And required lend lease Grants sent to the Soviet Union to be equipped with lower powered diesel engines. The British were indecisive on fuel requirements, their tanks vacillated between diesel and petrol power throughout the war.

So what is the difference between the "Grant" and the "Lee"? The short answer is the Grant was the version of the M3 that was shipped to England. The British insisted on some changes for their models. They gave the fitted radio suite to the tank commander, reducing the crew requirements from 7 to 6. And they produced their own turret for the M3, removing the cupola and supporting machine gun, thus reducing its profile.

When designed, the M3 was proof that you can meet all the customer’s specifications, and not give them what they wanted. However, the M3 has to be considered in the timeframe under which it was built. The Canadian built Lees were nick-named "A Coffin for Seven Brothers" by the Russians. The British even after experiencing horrendous looses in tanks, accepted the Grants only after serious modification to the design. But the enemy had a different point of view. After the Battle of Gazala, Rommel was shocked that the British had over 200 Grants with 7.5cm guns, while he only had 30 tanks with guns bigger than 3.7cm. He later wrote "At the end of 1941 the German Panzer III and Panzer IV were still superior to enemy types in range and caliber of guns and, in some measure, maneuverability. This advantage was held until May 1942, when our opponents found an answer with the Grants and Lees."

* The American theory of anti tank warfare at the time, as described by General Devers, was this, “The answer to the tank is the gun.” He reasoned it this way, “Why spend $35,000 for a tank, when we can spend $1,000 for the antitank gun.” This lead to the call up of over 220 independent anti-tank battalions. Where this theory fell apart was when you calculated the full cost of the manpower to drive the weapons systems. The antitank gun could kill a tank, providing it happened to be pre-deployed where the tank was going to be. But on average it took about 6 guns to kill one tank. With a crew of 3, this is 18 men. And the men were far more expensive to train, ship, and maintain than the gun or tank.

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