ARMOR-CAVALRY: Part 1; Regular Army and Army Reserve/Tank Design and Production
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- The devastating firepower and speed of the U.S. Army's armored divisions of World War II was largely the result of the genius of American industry. When Germany invaded western Europe in 1940, the U.S. Army had only 28 new tanks- 18 medium and 10 light- and these were soon to become obsolete, along with some 900 older models on hand. The Army had no heavy tanks and no immediate plans for any. Even more serious than the shortage of tanks was industry's lack of experience in tank manufacture and limited production facilities. Furthermore, the United States was committed to helping supply its allies. By 1942 American tank production had soared to just under 25,000, almost doubling the combined British and German output for that year. And in 1943, the peak tank production year, the total was 29,497. All in all, from 1940 through 1945, U.S. tank production totaled 88,410.
- Tank designs of World War II were based upon many complex considerations, but the principal factors were those thought to be best supported by combat experience. Among these, early combat proved that a bigger tank was not necessarily a better tank. The development goal came to be a tank combining all the proven characteristics in proper balance, to which weight and size were only incidentally related. Top priority went to mechanical reliability and firepower. Almost as important were maneuverability, speed, and good flotation (low ground pressure). Armor protection for the crew was perhaps less important, although it remained a highly desirable characteristic. The problem here was that only a slight addition to the thickness of armor plate greatly increased the total weight of the tank, thereby requiring a more powerful and heavier engine. This, in turn, resulted in a larger and heavier transmission and suspension system. All of these pyramiding increases tended to make the tank less maneuverable, slower, and a larger and easier target. Thicker armor plate beyond a certain point, therefore, actually meant less protection for the crew. Determining the point at which the optimum thickness of armor was reached, in balance with other factors, presented a challenge that resulted in numerous proposed solutions and much disagreement.
- According to Lt. Gen. Lesley J. McNair, Chief of Staff of GHQ, and later Commanding General, Army Ground Forces, the answer to bigger enemy tanks was more powerful guns instead of increased size. And, in his high positions, General McNair understandably exerted much influence upon the development of tanks, as well as antitank guns.
- Since emphasis of the using arms was upon light tanks during 1940 and 1941, their production at first was almost two to one over the mediums. But in 1943, as the demand grew for more powerful tanks, the lights fell behind, and by 1945 the number of light tanks produced was less than half the number of mediums.
- In early October 1939 the first tank order of the World War II period called for over 300 light (11 ½ tons) M2A4 tanks. The following year a much improved light tank, the M3, known in England as the General Stuart, was adopted. Although very similar to the M2A4, the M3 was 3 ½ tons heavier, mounted a 37-mm. gun, and had a maximum speed of 35 miles per hour. Several design changes resulted in a new model, the M4, but its number was soon changed to the M5 to avoid confusion with the M4 medium tank. The M5's weight was increased to 16 tons and its top speed to 40 miles per hour. With the trend toward heavier tanks and more powerful guns, the M5 was replaced in 1944 by the M24 light tank, mounting a 75-mm. gun and weighing 20 tons.
- In the medium tank class, improvements in the M2A1 resulted in a completely redesigned tank, known as the M3 medium. As originally produced, it weighed 31 tons and had a top speed of about 25 miles per hour. A 75-mm. gun was mounted in the right sponson and the 37-mm. gun remained in the turret. As furnished to the British under lend-lease, this first model of the M3 medium was known as the General Lee, which is sometimes confused with the later General Grant. The Grant was essentially the same vehicle except for its lower silhouette, achieved by removing the cupola from its turret.
- A much improved M3 medium was standardized in 1941 as the M4, better known throughout the war by its British designation, the General Sherman. It weighed around 33 tons and had a maximum speed of about 26 miles per hour. Built on the M3 chassis, the M4 mounted a 75-mm. gun that was, for the first time, in a fully rotating turret. By 1943, numerous redesigns of the M4 medium resulted in modified models mounting 76-mm. or 105-mm. guns, but through all of the changes the basic medium of the U.S. Army remained the M4 mounting the 75-mm. gun. Although it was no match for German heavy tanks in firepower and armor protection, the M4 medium, with its superior mechanical reliability and capacity for traversing rough terrain, especially in mountainous areas, was the workhorse of the war. Employed in practically every conceivable way that a tank could be used, it performed the infantry-accompanying role, it operated as light cavalry, it spearheaded armored attacks, it played an antitank role, and it functioned as auxiliary artillery.
- Although emphasis had been placed first upon the development of the light and then upon the medium tank during the early 1940's, there were those who favored a heavier tank. They were willing to sacrifice some speed and maneuverability for the additional shock and firepower primarily needed to overcome heavy fortifications in the direct support of infantry attacks. Several variations of a heavy tank were developed, the M6 being standardized in early 1943. Weighing about 63 tons, it mounted a 3-inch high-velocity gun. Test results achieved by the vehicle did not justify its tremendous weight and, also, since medium tanks were adequately proving themselves in combat in North Africa, the War Department decided to provide for only one heavy tank company.
- Continued experiments toward the development of a more reliable heavy tank were largely inspired by the appearance in 1943 of German heavy Panther (47-ton) and Tiger (63-ton) tanks. Great technical strides were made not only in more powerful guns, better armor, and more powerful engines, but also in the transmission and suspension mechanisms. Furthermore, the search was continuous for more effective ammunition and less weight in all components. Finally, a successful heavy tank, the M26 or General Pershing, was developed in time for a few to be used in Europe late in the war. Mounting a 90-mm. gun, it weighed approximately 46 tons and had a maximum speed of 25 miles per hour. Although their engagements were limited, the new M26 heavies were very popular with the U.S. Army units with which they fought.
- There were several other types of World War II tanks that can be classified as special purpose. In organizations generally of battalion size, they were usually modifications or adaptations of standard tanks and were designed for the specific type of missions intimated by their unit designations. They included amphibious (DD, or duplex-drive, and LVT, or landing vehicle, tank), airborne, searchlight, mine exploders, earth movers (tankdozer and "Rhino," or "Hedgerow Buster," very successfully used in hedgerows of Normandy), flamethrowers, and rocket launchers. Also, a tank for battlefield illumination that projected a light beam through a 2-by-24inch slit from a searchlight mounted in the turret instead of a 37-mm. gun. Developed behind a tight curtain of secrecy and known simply as the CDL (canal defense light) tank, it was described as a highpowered searchlight for the defense of the Suez Canal. Its combat use was limited to the Rhine River crossings in early 1945.