M26 Pershing
The M26 Pershing is a heavy tank, later designated as a medium tank, formerly used by the United States Army. It was used in the last months of World War II during the Invasion of Germany and extensively during the Korean War. The tank was named after General of the Armies John J. Pershing, who led the American Expeditionary Force in Europe during World War I.
The M26 was intended as a replacement of the M4 Sherman, but a prolonged development period meant that only a small number saw combat in Europe. Based on the criteria of firepower, mobility, and protection, US historian R. P. Hunnicutt ranked the Pershing behind the German Tiger II heavy tank, but ahead of the Tiger I heavy and Panther medium tanks. It was withdrawn in 1951 in favor of its improved derivative, the M46 Patton, which had a more powerful and reliable engine and advanced suspension. The lineage of the M26 continued with the M47 Patton, and was reflected in the new designs of the later M48 Patton and M60 tank.
Production history
Development
The M26 was the culmination of a series of medium tank prototypes that began with the T20 in 1942, and it was a significant design departure from the previous line of U.S. Army tanks that had ended with the M4 Sherman. Several design features were tested in the prototypes. Some of these were experimental dead-ends, but many became permanent characteristics of subsequent U.S. Army tanks. This series of prototype vehicles began as a medium tank project that was similar to, but more modern than the recently introduced M4 Sherman, and ended several years later as the U.S. Army's first operational heavy tank.Improving on the M4
The U.S. Army's first lineage of tanks evolved from the M1 Combat Car and progressed to the M2 Light Tank, M2 Medium Tank, M3 Lee, and finally the M4 Sherman. These tanks all had rear-mounted Continental air-cooled radial aircraft engines and a front sprocket drive. This layout required a driveshaft to pass under the turret, which increased the overall height of the tank, a characteristic shared with German tanks of World War II that also used this layout. The large diameter of the radial engines in M4 tanks added to the hull height. These features accounted for the high silhouette and large side sponsons that were characteristic of the M4 lineage.In the spring of 1942, as the M4 Sherman was entering production, U.S. Army Ordnance began work on a follow-up tank. The T20 tank reached a mock-up stage in May 1942, and was intended as an improved medium tank to follow the M4. An earlier heavy tank, the M6, had been standardized in February 1942, but proved to be a failure. The U.S. Army had no doctrinal use for a heavy tank at the time.
T20
The T20 was designed to have a more compact hull than the M4. The Ford GAN V-8, a lower silhouette version of the GAA engine used in later variants of the M4, had become available. The engine had originally been an effort by Ford to produce a V-12 liquid-cooled aircraft engine patterned after the Rolls-Royce Merlin, but failed to earn any aircraft orders and so was adapted as a V-8 for use in tanks; use of this lower profile engine together with the choice of a rear transmission and rear sprocket drive layout made it possible to lower the hull silhouette and eliminate the side sponsons.The T20 was fitted with the new 76 mm M1A1 gun, the 3-inch M7 was considered too heavy at about. New stronger steels were used to create a weapon weighing about 1,200 lb. The 3 inch front hull armor was thicker than the front armor of the M4. The glacis plate slope was similar at 46°. The T20's overall weight was approximately the same as the M4.
The T20 used an early version of the horizontal volute spring suspension, another improvement compared to the less robust vertical volute spring suspension of the early versions of the M4. Later prototypes of the M26 tested a torsion bar suspension, which became the standard for future U.S. tank suspension systems.
T22 and T23
The T22 series reverted to the M4 transmission because of problems with the early Torqmatic transmission used in the T20. The T22E1 tested an autoloader for the main gun and eliminated the loader's position with a small two-man turret.Through much of 1943, there was little perceived need within the U.S. Army for a better tank than the 75 mm M4 Sherman, and so, lacking any insights from the rest of the Army as to what was needed, the Ordnance Department then took a developmental detour into electrical transmissions with the T23 series.
The electrical transmission was built by General Electric and had the engine driving a generator that powered two traction motors. The concept was similar to the drive system of the German "Porsche Tiger". It had performance advantages in rough or hilly terrain, where the system could better handle the rapid changes in torque requirements.
The electrical transmission T23 was championed by the Ordnance Department during this phase of development. After the initial prototypes were built in early 1943, an additional 250 T23 tanks were produced from January to December 1944. These were the first tanks in the U.S. Army with the 76 mm M1A1 gun to go into production. However, the T23 would have required that the army adopt an entirely separate line of training, repair, and maintenance, and so was rejected for combat operations.
The primary legacy of the T23 would thus be its production cast turret, which was designed from the outset to be interchangeable with the turret ring of the M4 Sherman. The T23 turret was used on all production versions of the 76 mm M4 Sherman as the original M4 75 mm turret was found to be too small to easily mount the 76 mm M1A1 gun. The first production 76 mm M4 with the T23 turret, the M4E6, was built in the summer of 1943.
T25 and T26
The T25 and T26 lines of tanks came into being in the midst of a heated internal debate within the U.S. Army from mid-1943 to early 1944 over the need for tanks with greater firepower and armor. A 90 mm gun mounted in a massive new turret was installed in both series. The T26 series were given additional frontal hull armor, with the glacis plate increased to. This increased the weight of the T26 series to over and decreased their mobility and durability as the engine and powertrain were not improved to compensate for the weight gain.The T26E3 was the production version of the T26E1 with a number of minor modifications made as the result of field testing. In February 1945, the T26 was fielded in the European Theater, where its performance received early praise from Army Ordnance officials. The Army named the tank after Army General John J. Pershing when it was redesignated the M26 in March.
After the war
After World War II, some 800 M26 tanks were upgraded with improved engines, transmissions, and the improved 90mm gun M3A1. These were designated as the M26E2 and later redesignated as M46 Patton.Delayed production
The M26 was introduced late into World War II and saw only a limited amount of combat. Tank historians, such as R. P. Hunnicutt, George Forty and Steven Zaloga, have generally agreed that the main cause of the delay in production of the M26 was opposition to the tank from the Army Ground Forces, headed by General Lesley McNair. Zaloga in particular has identified several specific factors that led both to the delay of the M26 program and limited improvements in the firepower of the M4:; 1.
; 2.
; 3.
From mid-1943 to mid-1944, development of the 90 mm up-armored T26 prototype continued to proceed slowly due to disagreements within the U.S. Army about its future tank needs. The accounts of what exactly happened during this time vary by historian, but all agree that Army Ground Forces was the main source of resistance that delayed production of the T26.
In September–October 1943, a series of discussions occurred over the issue of beginning production of the T26E1, which was advocated by the head of the Armored Force, General Jacob Devers. Ordnance favored the 76 mm gun, electrical transmission T23. Theater commanders generally favored a 76 mm gun medium tank such as the T23 and were against a heavy 90 mm gun tank. However, testing of the T23 at Fort Knox had demonstrated reliability problems in the electrical transmission of which most army commanders were unaware. The new 76 mm M1A1 gun approved for the M4 Sherman seemed to address concerns about firepower against the German tanks. Although it could reliably penetrate the frontal armor of a Tiger 1 at standard ranges, all participants in the debate were, however, unaware of the inadequacy of the 76 mm gun against the frontal armor of the Panther tank, specifically its upper glacis, as they had not researched the effectiveness of this gun against the new German tanks, which had already been encountered in combat.
Gen. Lesley J. McNair had agreed to the production of the 76 mm M4 Sherman, and he strongly opposed the additional production of the T26E1. In the fall of 1943, he wrote this letter to Devers, responding to the latter's advocacy of the T26E1:
General Devers pressed on with his advocacy for the T26, going over McNair's head to General George Marshall, and, on 16 December 1943, Marshall overruled McNair and authorized the production of 250 T26E1 tanks. Then, in late December 1943, Devers was transferred to the Mediterranean, where he eventually led the invasion of Southern France with the 6th Army Group. In his absence, further attempts were made to derail the T26 program, but continued support from Generals Marshall and Eisenhower kept the production order alive. Testing and production of the T26E1 proceeded slowly, however, and the T26E1 did not begin full production until November 1944. These production models were designated as the T26E3.
A single prototype of a T26 turret mounted on an M4 chassis was built by Chrysler in the summer of 1944, but did not progress into production.
Hunnicutt, researching Ordnance Department documents, asserts that Ordnance requested production of 500 each of the T23, T25E1, and T26E1 in October 1943. The AGF objected to the 90 mm gun of the tanks, whereas the Armored Force wanted the 90 mm gun mounted in a Sherman tank chassis. General Devers cabled from London a request for production of the T26E1. In January 1944, 250 T26E1s were authorized. General Barnes of Ordnance continued to press for production of 1,000 tanks.
According to Forty, Ordnance recommended that 1,500 of the T26E1 be built. The Armored Force recommended only 500. The AGF rejected the 90 mm version of the tank and wanted it to be built with the 76 mm gun instead. Somehow, Ordnance managed to get production of the T26E1 started in November 1944. Forty primarily quoted from a post-war report from the Ordnance Dept.