In the meantime, we began to receive M4A1 medium tanks with a long-barreled 76mm gun with a muzzle velocity of 2,650 feet per second. Considering that the penetrating capacity of the projectile varies as the square of the muzzle velocity, even the Mark IV outgunned both our M4 and M4A1.
When we ran into the German PzKw V Panther, a fifty-two-ton tank with three and a half inches of armor on a thirty-eight-degree glacis plate, compared to two and a half inches of armor at forty-five degrees on the M4, we were grossly outgunned. The Panther carried the even more powerful 75mm KwK42 gun, with a muzzle velocity of 3,300 feet per second. The myth that our armor was in any way comparable to German armor was completely shattered. We realized that we were fighting against German tanks that were far superior to anything we had to offer. As a result, many young Americans would the on the battlefield.
This situation had been further aggravated by command decisions made earlier. After arriving in England in January 1944, General Eisenhower had ordered some of the division commanders and staff officers to report to Tidworth Downs, the main ordnance depot for armored equipment in the European theater, where all the latest ordnance equipment available at the time was demonstrated. The operation was code-named for an ordnance colonel from Aberdeen Proving Ground who came over to perform the demonstration.
Many general officers from the U.S., British, and Canadian armies had attended plus a number of high-ranking colonels and other field-grade officers. The maintenance battalion of the 3d Armored Division was stationed at Codford Saint Mary, a short distance from Tidworth Downs. Some of our maintenance people who had been detailed to this demonstration to provide maintenance support for the armored weapons systems told us what they had seen. When I visited Tidworth Downs fifty years later, the post historian told me that no records of the demonstration exist other than to note that it took place.
First to be demonstrated were infantry weapons systems, including small arms, machine guns, and mortars.
Particularly impressive was the firepower of the M1 Garand rifle in comparison to that of the German Mauser, of World War 1 vintage. There was some concern that our .30-caliber machine guns, also of World War I vintage, had a much lower cyclic rate of fire than the German machine guns; however, the Germans had no counterpart for our .50-caliber machine gun. Our 60mm and 81mm mortars appeared comparable to the German weapons, and our 4.2-inch chemical mortar was an excellent weapon for laying down white phosphorus smoke shells.
Artillery was demonstrated next. Although it could not be fired due to lack of range, aspects of various pieces were demonstrated, particularly the unlimbering setup and relimbering preparatory to movement. The 105mm howitzer, the 155mm howitzer, the 155mm rifle (Long Tom), the 8-inch howitzer, the 8-inch gun, and the 240mm howitzer were all of modern design, were completely motorized, and had pneumatic tires for high-speed highway transport. This equipment was equal or superior to the German guns, because the Germans still used a great deal of horse-drawn artillery.
Finally, the armored weapon systems were reviewed. First came the armored artillery. The M7, a modified M3 tank carriage with a 105mm howitzer and a .50-caliber ring-mounted machine gun, proved an excellent weapon. The M12, another modified M3 medium tank chassis, carried a 155mm GPF rifle of World War I vintage. Even though this weapon did not have the muzzle velocity of the newer 155mm Long Tom, it proved to be extremely effective. The 991st Field Artillery Battalion, equipped with these Ml2 gun carriages, was attached to the 3d Armored Division throughout the European operation.
Next came the antitank weapons. The small 37mm antitank gun, already obsolete, was being replaced by the 57mm antitank gun, which was still inferior to the German PAK41. The 90mm gun was a dual-purpose weapon that had been originally developed as an antiaircraft gun. In addition, it could be lowered to a horizontal position and used as an antitank gun. It was similar to the German 88mm; however, it had a lower muzzle velocity than the 88 and therefore was not as effective an antitank weapon.
Then came the tanks. The M5 light tank was demonstrated first. It had an inch and a half of armor at forty-five degrees on the glacis plate and an inch of armor on the sides. It was equipped with a 37mm antitank gun in the turret, two .30-caliber machine guns, and a .50-caliber ring mount. It had two Cadillac engines driving a hydramatic transmission, which proved to be a good power train that provided considerable mobility and speed.
The M5 was a good, fast light tank, although it was too light to be engaged in firefights with German tanks and was already considered obsolete. It was being replaced by the M24 light tank, which was still in production in the States and would not be received until we were well into Central Europe. Instead, films of this tank were shown. The M24 was between the M5 and the German Mark IV in size, had a wider track system than either of them, weighed approximately twenty tons, and was the first American tank equipped with Christy suspension. It had better armor protection than the M5 and also had a 75mm gun. The muzzle velocity was still too low to be effective against German armor.
Our main battle tank, the M4, was demonstrated next. It had two and a half inches of armor at forty-five degrees on the front glacis plate and an inch and a half to two inches on the side of the hull and on the sponsons. The turret had three to four inches on the front and two inches on the side plus a five-inch mantlet that fitted over the gun tube and raised and lowered with the gun. The tank had two .30-caliber machine guns, one in a ball mount in front of the assistant driver and one in the turret coaxial with the main gun. There was also a .50-caliber machine gun on a ring mount on top of the turret. The tank’s main armament consisted of a short-barreled 75mm M2 gun with a muzzle velocity of 2,050 feet per second. The tank had narrow tracks with a ground bearing pressure of approximately seven pounds per square inch on the ground. Theoretically, this was about the same pressure that a man exerted walking on soft ground; it was felt that if a man could walk across the ground, a tank could also negotiate it. This was almost twice the ground bearing pressure per square inch of the German tanks.
The M4A1 was shown next. It was essentially the same tank as the M4 but with an improved high-velocity 76mm gun and a different turret to accommodate it. This was a vast improvement over the M4, but the gun was still less powerful than the German KwK41. By the time we arrived in Normandy, between 10 and 15 percent of our tanks carried the 76mm, and thereafter almost all replacements were 76s.
From our experience in North Africa, it had been belatedly recognized that both the M4 and the M4A1 were inadequately protected. Thus, we had arranged with the British main ordnance depot at Warminster to modify all of our M4 tanks by putting one-inch armor patches over the three ammunition boxes and quarter-inch armor inside the sponsons and also underneath the turret. We also put an additional two-inch armor patch in front of the driver’s periscope and the assistant driver’s periscope on the front of the glacis plate. All the new tanks coming off the production line in the States already had this modification before they were shipped to England.
The next demonstration opened up a can of worms that placed rank and authority against knowledge and experience, and pitted the narrow interpretation of tactical doctrine against flexible response to meet new, changing conditions. A new heavy tank known as the M26 Pershing had just been developed and was ready for production. There was no working model of this tank in England at the time, but films of it were shown.
The tank had been thoroughly tested and approved by both the ordnance and armored forces boards. The Tank Automotive Center in Detroit was prepared to go into full production immediately upon receipt of a go-ahead from Supreme Headquarters, Allied Expeditionary Force (SHAEF). Because of the urgency of this project, a high priority had been granted by the War Production Board to proceed immediately, and schedules had been prepared that would allow these tanks to be delivered in time for the invasion.