America's Improved World War II Tanks

Before the American Stuarts, Lees, Grants, and Shermans had been combat proven, far-sighted people, particularly in the U. S. Army Ordnance Department, began planning anew generation of tank designs. They expected the Germans to introduce improved tanks, and America would need improved tanks to fight them. Time would prove them absolutely correct. Development began before the first American tanks reached full production in 1941. Before America had entered the war, the Army's tank research and development program had been based on willing cooperation between the Army and industry. When the country entered the war, this cooperation became much more intense in what President Franklin D. Roosevelt called "the arsenal of democracy." Although the major stress was to produce the arms and equipment required to fight the war, the country's entire industrial research and development establishment supported tlie war effort. Before the end of tlie war, this cooperation helped the U. S. Army introduce three entirely new and improved tanks. These were the 76-mm Gun Motor Carriage M18 "Hellcat," the 75-mm gun light tank M24 "Chaffee," and the 90-mm gun heavy (later medium) tank M26 "Pershing." Many of the basic improvements introduced with them will be found in today's tanks and other armored fighting vehicles. The major improvements incorporated in these tanks stemmed from experimental work done by the U. S. Army Ordnance Department in the 1930s, particularly on tracks, suspensions, and power trains. At that time, several early model Stuart light tanks were built with experimental suspensions. One of these, the Combat Car T6, was equipped with anew concept, "torsion bar suspension," invented by General Gladeon M. Barnes of the Ordnance Department. At the same time, the Ordnance Department tested anew center guide rubber-bushed track to replace its successful edge-guided rubber-bushed track. This was an improvement on the center guide track design inventor Walter P. Christie had pioneered during and just after World War I. Tests showed the torsion bar suspension was superior to the volute spring suspension already successfully in use because it gave the bogie wheels almost double the volute spring suspension's travel. The torsion bar suspension could also easily use a shock absorber, which was difficult, if not impossible, to use on the volute suspension. The center guide track was also superior to the edge-guided type because it was easier to modify ARMOR - November-December 7990 39

The MI8 Hellcat: While it could hit as much as 75 miles-per-hour on a good surface, it was governed to 55 miles-per-hour, a speed which was classified during the war. and harder to throw off the suspension. However, while all this had been shown by the time America entered the war, the urgency of wartime requirements was too great to permit changes in existing production designs. The torsion bars themselves also proved difficult to produce because of materials and surface finish problems. However, about the time America entered the war in 1941, development work on the latest thing in armored fighting vehicles, the tank destroyer, began with serious consideration of the torsion bar suspension and center-guided track. Wartime urgency kept its progress slow. Buick Division of General Motors Corporation was selected to build the experimental new tank destroyer. The first prototype was the 37-mm Gun Motor Carriage T49. Before the project had gotten very far, designers changed the gun to the British 57-mm tank-antitank gun, which the U. S. Army had hastily adopted. The T49 had torsion bar suspension, center-guided track, and another remarkable innovation contributed by General Motors: a rear track drive with a "Torquematic" automatic transmission. While this vehicle showed great promise in tests in the summer of 1942, the rapidly changing armored combat conditions required more changes. The requirement for more powerful armament for tank destroyers led to anew Buick-built prototype: the 75-mm Gun Motor Carriage T67. It incorporated a host of detail improvements and the same 75-mm gun used in the Sherman tank, but by the time it was tested in the late fall of 1942, an even more powerful gun was needed. The Ordnance Department had developed anew lightweight version of the standard three-inch tank and antitank gun, including an ammunition change, which was designated the 76-mm tank and antitank gun. Six modified T67 prototypes mounting the new 76-mm gun were built, and after testing, it was recommended for production in February

1943. However, one major change was required: the track drive was to be in front instead of the rear. Buick built this version very quickly as the 76-mm Gun Motor Carriage T70, and it was adopted for "limited production" in July 1943. It was standardized in February 1944 as the 76-mm Gun Motor Carriage M18 "Hellcat," and it was a truly remarkable vehicle by any standards. The 20-ton Hellcat was powered by the same 400-horsepower modified, air-cooled, radial aircraft engine used in the 32-ton Sherman, giving the Hellcat the highest power-to-weight ratio of any armored combat vehicle of its day. Its automatic transmission worked well, and it had as high an operating speed as any armored fighting vehicle ever built. It regularly operated at sustained road speeds of 45 miles-per-hour, and often terrified American car and truck drivers adhering to the 35-mile-per-hour wartime national speed limit. While it could hit as much as 75 miles-per-hour on a good surface, it was governed to 55 miles-per-hour, a speed which was classified during the war. MI8 Hellcat tank destroyers being assembled at the GM Buick plant in Flint, Michigan. Like the M26 and M24, the MI8 had torsion bar suspension. The MI8 could do 75 MPH. ARMOR - November-December 7990 40 t An M18 Hellcat supports infantry in the streets of Brest, France in September 1944. As a tank destroyer, the Hellcat was more lightly armored than even alight tank. Its armor was about the same as the "splinter proof' protection of the U. S. Army World War I1 half-track. The Hellcat first saw combat in Europe in the summer of 1944, and it proved to be an outstanding tank destroyer. Using its speed and "shoot and move'' tactics, German tanks and antitank guns could not keep up with it. The record of the 609th Tank Destroyer Battalion is a good example. It went into action in northwestern Europe in October

1944. With the latest ammunition, its 76-mm guns could knock out anything the Germans had, up to Panther and Tiger family vehicles. In the Battle of the Bulge, the 609th knocked out more than 20 German tanks with a loss of two Hellcats. A New Light Tank As soon as the Stuart light tank had gone into combat in 1941, the U. S. Army Ordnance Department recognized that it needed improvement, and eventual replacement. In 1942, it asked Cadillac Division of General Motors to borrow technology from Buick to develop anew light tank. The project moved slowly due to other wartime requirements, but in March 1943, limited production of anew 75-mm gun light tank T24 was authorized. It was a massive improvement over the Stuart. One key improvement was anew lightweight 75-mm gun, the first mounted in alight tank. While it tired the same ammunition as the Sherman's 75, it only weighed half as much: 406 pounds. This 75 was a modification of the lightweight 75 used to arm U. S. Army Air Force North American B25. Mitchell ground attack aircraft. The 20-ton T24 had well designed light tank *: c? -.. Although a number of experimental vehicles were built on the Hellcat chassis, only one went into production. It was the U. S. Army's first production purpose-built, full-tracked armored personnel carrier: the Armored Utility Vehicle T41, later standardized in 1945 as the Armored Utility Carrier M39. It saw little combat use in World War 11, but it is the first in the line leading to today's armored personnel carriers. cise -was based on the M18 Hellcat chassis. It saw little action in WWII. ARMOR - November-December 7990 47

Chaffee light tanks patrol a forest road near Haultnausen, bermany in Marcn 1 4 3. r - u " - - ared to a common output, and M19 (T65). It mounted ed a hydramatic automatic trans-cooled modification of ission with a front track drive. Its Navy's water-cooled shipb p speed was more than 35 miles- 40-mm Bofors autom:r-hour, and it could sustain tiaircraft gun. The b eeds of 25 miles-per-hour, excel-developed in anticipation I *+ ffi- th- t: - 111 menAqqo- r++nnnpr r.p+m-n Air Fnrp armor. It was driven by a pair of Cadillac V8 nassenger car eneines ge mi to1 Pe SP leilr lul L1lb L1llb. LIIIIIIbu yzvuub-tion" of the T24 began in September 1943, and it was standardized as the 75-mm Gun Light Tank M24 "Chaffee" in July 1945. By that time, it had been in combat for several months. The Chaffee proved very successful in action, and by the end IS com- r model us. _^... -.-. or IYW, the u.3. Army wi mitted to replace all its olde light tanks with Chaffees. A greal deal of the Chaffee's success was due to its superior chassis, which was used for a number of other vehicles. The first was the Twin 40-mm Gun Motor Carriage I an air-the U. S. loard twin atic an- d19 was of a much oravxx5V. V1........... - -.:e than existed, and it was hardly committed in World War I1 because it was not required. Like all Chaffee vehicles, it proved very successful in Korea. The Chaffee chassis was the basis for two very successful self-propelled artillery pieces. One was the 105-mm Howitzer Motor Carriage M37 (T76), a replacement for the Sherman-chassis-based 105-mm self-propelled M7 "Priest." The M37 used a 105-mm howitzer, originally developed for the infantry support 105-mm-armed Sherman tank. The other Chaffee self-propelled gun was the 155-mm Howitzer Motor Carriage M42 (T64). Ab though both this and the 105-mm howitzer M37 were both in production before the end of the war, there was no urgent need for them and they did not see any combat. Both were used in Korea with good success, and remained in use for many years. All the Chaffee family vehicles not only served with distinction in Korea, but they remained U. S. Army "Standard B" well into the 1960s. They will still be found in service in some military establishments, and many elements of the chassis are practically identical to those of tracked vehicles in current service. M26 Pershing Medium Tank Unlike the Hellcat and Chaffee, the development of the 90-mm gun M26 Pershing tank was along, complicated program. It began when the U. S. Army adopted the M4 Sherman, and the Ordnance Department looked at ways to improve it. It began in 1942 with two major considerations: to improve the Sherman's silhouette, and to arm it with a more powerful gun. This led to a series of experimental tanks known as the T20s. The first of the T20s mounting the new high-velocity 76-mm gun were built in 1942. There were several prototypes using as much of the Sherman as possible but with anew flatter hull and modified turret. Several had automatic transmissions, and some had rear track drive. Some used Shcrman suspensions, some anew torsion bar type. They all weighed about the same as 42 ig at war were rare because the tank only saw action in the later stages Seen here with its 90-mm gun tube over hotos of the M26A3 Perst the rear deck. this 9th Armored Division M26 is near Vettweiss, Germany in March 1945. the Sherman, 33 tons, and were deemed "promising,ll but none of them went into even limited production. But, 1942 was not the year for the introduction of new tank designs. The requirements of the U. S. Army and its allies, equipped under Lend-Lease agreements, was too urgent. The U. S. Army Ground Forces Command and the Armored Force Board observed the success of the existing tanks in combat, and were convinced that they needed improved versions of existing tanks, and not new ones. However, improvements in German tanks were coming very quickly. When the Armored Force Board considered the T2Os in late 1942, it requested a large number of changes and improvements, and the T20 series went back to the designers for more work. In October 1942, the Chrysler-operated Detroit Tank Arsenal was ordered to produce two experimental T22 tanks with the requested changes and improvements. They had an improved Sherman-type volute spring suspension and track, and they mounted the 76-mm gun. They also had a number of power train changes. They were not particularly successful, but they indicated what was needed. An experimental automatic loading 75- mm gun was temporarily mounted on one T22, but it was not satisfactory. Following right behind the T22s were the T23s, authorized in early

1943. These had improved armor and the 76-mm gun. T23s included versions built with both the Sherman-type suspcnsion and a torsion-bar type, and an experimental gasoline-electric drive. This last was a system similar to that used in diesel-electric locomotives, and it was, at best, marginally satisfactory. The T23s all weighed about 36 tons. Although the T23s had some superior features, which looked very promising, they were only built in limited numbers for experimental work. However, improvements in German tanks and other considerations again sent the T20 scries back to the drawing board. One of the new considerations was to arm anew tank with a 90-mm gun. A 90-mm gun, adapted from the 90-mm antiaircraft gun, had already been fieldcd on the M36 tank destroyer. Until mid-1943, the Army Ground Forces Command and the ARMOR - November-December 7990 43

Armored Force Board had questioned the need for a 90-mm gun, but the need for it was now recognized. One was satisfactorily mounted in a T23 prototype, but by then, another redesign was underway. The next version was the 90-mm gun "25, built with the new, much improved HVSS suspension with its new wider center guide track (M4A3E8). This model was superior to any other tank in service. Another version, the T25E1 was built with a torsion bar suspension with a center guided track, and it was also successful. Both the T25s used anew "hydramatic" automatic transmission with anew Ford GAF V8 water-cooled gasoline engine, which was very satisfactory. Fifty T25 prototypes, 25 of each suspension type, were completed in January 1944, and they went under "field testing" by the Armored Force. The T25s weighed some 38 tons and were well armored, but by 1944, Army Ground Forces Command and Armored Force Board observations of the latest German tanks led them to request improved protection. At this point, the needs and urgent requirements for the Normandy invasion of Europe in June 1944 delayed the program. To further complicate things, Army Ground Forces Command and the Armor Force Board were unable to decide which suspension they wanted for the new tank. The Ordnance Department recommended the torsion-bar type, the ultimate choice, because of its success on the Hellcat and Chaffee. Anew 46-ton T26 uparmored version of the T25E1 was built with a 90-mm gun and torsion bar suspension. It was authorized for limited production in October 1944. A number of changes made it the T26E3. The T26E3 was standardized as the 90-mm gun heavy tank M26 "Pershing" in May 1945, but it had seen combat six months before. About the time the war ended in August 1945, the M26 heavy Pershing was redesignated the 90-mm gun medium tank M26 "Pershing" because even heavier tanks were in the experimental stage. The Pershing was a superior tank for its day, and its basic design still influences main battle tank designs. The Pershing's torsion bar suspension gave it an easy ride and made it a superior moving gun platform. Its heavy armor and powerful 90- mm gun allowed it to fight the vaunted German Panthers and Tigers on equal terms. Its power train had problems, but these were corrected after the war. The fvst 20 Pershmgs were shipped to Europe on an "emergency" basis in January 1945, and immediately issued to the 3rd and 4th Armored Divisions. Although their numbers were very small, they went into action before the U. S. Army crossed the Rhine River. Six of them were used in the Rhine crossing at Wesel, and several were in the famous Remagen Bridge fight. Although the Pershing proved its superiority, the rapid collapse of the German armed forces kept many from catching up with the action. A handful of Pershmgs, and a few of the infantry support 105-mm howitzer heavy tank M45 version, were committed on Okinawa in late

1945. The Japanese had nothing but massive land mines and heavy field artillery that could bother them. Although a number of experimental models were built, the Pershing did not become the basic chassis for any other vehicles. The Pershing, however, is the basis of the U. S. Army tank designs from the M46 The Pershing's torsion bar suspension gave it an easy ride and made it a superior moving gun plafform. Its heavy armor and powerful 90- mm gun allowed it to fight the vaunted German Panthers and Tigers on equal terms. used in Korea up to today's M1. The improved American World War I1 tanks, the Hellcat, Chaffee, and Pershing, introduced many tank design features still in use. Note This analysis was based on official reports, manuals, and other documents pertaining to U. S. Army tanks and their development in World War 11, Army Ordnance magazine, and other military journals. Other sources include the published and unpublished writings of General Gladeon M. Barnes, U. S. Army Chief of Development and Engineering for the Ordnance Department during World War 11. The author has also consulted several other credible unauthorized U. S. Army tank histories, and a number of unit histories. Konrad F. Schreier, Jr. is a professional technological and military historian who served in the China-Burma-India Theater in World War I t and later graduated from the U. S. Army Ordnance School at Aberdeen Proving Ground, Md. He was a civilian engineer from 1950 to 1967, when he became a full-time historian, specializing in U. S. Armed Forces history. He is a Fellow of the Company of Military Historians and a member of the U. S. Commission on Military History. - 44 ARMOR - Novernber-December 799G