The M4 Sherman, officially Medium Tank, M4, was the medium tank most widely used by the United States and Western Allies in World War II. The M4 Sherman was reliable and well adapted to mass production. Tens of thousands were distributed through the Lend-Lease program to the British Commonwealth, Soviet Union, and other Allied Nations. The tank was named by the British after the American Civil War General William Tecumseh Sherman. It was also the basis of several other armored fighting vehicles including self-propelled artillery, tank destroyers, and armored recovery vehicles.
The M4 Sherman tank evolved from the earlier M3 Lee. The M3's unconventional layout and the limitations of its hull-mounted gun prompted the need for a more efficient and versatile design, leading to the development of the M4 Sherman.
The development of the M4 Sherman emphasized key factors such as reliability, ease of production, and standardization. The U.S. Army and the designers prioritized durability and maintenance ease, which ensured the tank could be quickly repaired in the field. A critical aspect of the design process was the standardization of parts, allowing for streamlined production and the efficient supply of replacement components. Additionally, the tank's size and weight were kept within moderate limits, which facilitated easier shipping and compatibility with existing logistical and engineering equipment, including bridges and transport vehicles.
The M4 Sherman became the most-produced American tank of World War II with a total of 49,324 units built, including various specialized variants. The only World War II-era tank to exceed the M4's production numbers was the Soviet T-34, with approximately 84,070 units built.
When the M4 tank first went into combat in North Africa with the British Army at the Second Battle of El Alamein in late 1942, it increased the advantage of Allied armor over Axis armor and was superior to the lighter German and Italian tank designs. Its 75 mm gun and better armor provided an edge over the tanks fielded by Nazi Germany at this time, though by 1944 the M4 was inferior in firepower and armor compared to the increasing numbers of German upgraded medium tanks and heavy tanks (most M4 Shermans kept their dual-purpose 75 mm gun into 1944.) but was able to fight on with the help of considerable numerical superiority, greater mechanical reliability, better logistical support, and fire support from growing numbers of fighter-bombers and artillery pieces. Later in the war, a more effective armor-piercing gun, the 76 mm gun M1, was incorporated into production vehicles. To increase the effectiveness of the Sherman against enemy tanks, the British refitted some Shermans with a 76.2 mm Ordnance QF 17-pounder gun (as the Sherman Firefly).
The M4 Sherman was instrumental in the success of several Allied offensives, particularly after 1942, when the Allies began to gain momentum following the Allied landings in North Africa (Operation Torch) and the subsequent campaigns in Italy and France.
The ability to produce the Sherman in large numbers, combined with its operational flexibility and effectiveness, made it a key component of the Allied war effort. The Sherman's role as the backbone of U.S. armored forces in World War II cemented its legacy as one of the most influential tank designs of the 20th century despite its limitations, such as thinner armor compared to German heavy and medium tanks like the Tiger and Panther.
After World War II, the M4 Sherman, particularly the many improved and upgraded versions, continued to see combat service in many conflicts around the world, including the UN Command forces in the Korean War, with Israel in the Arab–Israeli wars, briefly with South Vietnam in the Vietnam War, and on both sides of the Indo-Pakistani War of 1965. In US service, the M4 was replaced by the heavier M26 Pershing and M46 Patton.
U.S. prototype
The United States Army Ordnance Department designed the M4 medium tank to replace the M3 medium tank. The M3 was an up-gunned development of the M2 medium tank of 1939, in turn, derived from the M2 light tank of 1935. The M3 was developed as a stopgap measure until a new turret mounting a 75 mm gun could be devised. While it was a big improvement when used by the British in Africa against German forces, the placement of a 37 mm gun turret on top gave it a very high profile, and the unusual side-sponson mounted main gun, with limited traverse, could not be aimed across the other side of the tank. Though reluctant to adopt British weapons into their arsenal, the American designers were ready to accept proven British ideas. These ideas, as embodied in a tank designed by the Canadian General Staff, also influenced the development of the American Sherman tank. Before long American military agencies and designers had accumulated sufficient experience to forge ahead on several points. In the field of tank armament, the American 75 mm and 76 mm dual-purpose tank guns won the acknowledgement of British tank experts. Detailed design characteristics for the M4 was submitted by the Ordnance Department on 31 August 1940, but the development of a prototype was delayed while the production designs of the M3 were finished and the M3 entered full-scale production. On 18 April 1941, the U.S. Armored Force Board chose the simplest of five designs. Known as the T6, the design was a modified M3 hull and chassis, carrying a newly designed turret mounting the M3's 75 mm gun. This would later become the Sherman.
The Sherman's reliability resulted from features developed for U.S. light tanks during the 1930s, including vertical volute spring suspension, rubber-bushed tracks, and a rear-mounted radial engine with drive sprockets in front.
The T6 prototype was completed on 2 September 1941. The vehicle's "Turret Indirect Sighting Device" for the gunner, featured an optical periscope locked to the turret rotation, and housed in an armored casemate (with an armored shutter that rotated open or closed). Given the synecdoche label "Rotor", 30 (or more) rotor Shermans were produced. The upper hull of the T6 was a single large casting. It featured a single overhead hatch for the driver and escape hatches in the left and right side of the hull. In the later M4A1 production model, this large casting was maintained, although the side hatches were eliminated, and a second overhead hatch was added for the assistant driver. The modified T6 was standardized as the M4, and first production completed in February 1942. The cast-hull models would later be re-standardized as M4A1, with the first welded-hull models receiving the designation M4. In August 1942, a variant of the M4 was put forth by the Detroit Arsenal to have angled, rather than rounded hull and turret armor.
Doctrine
As the United States approached entry into World War II, armor usage was governed by Field Manual 100–5, Operations (published May 1941, the month after the M4 final design). That manual stated:
The M4 was, therefore, not intended primarily for infantry support. It placed tanks in the "striking echelon" of the armored division and placed the infantry in the "support echelon", without directing that tanks should only seek to attack other tanks, thus leaving target selection up to the field commander based on what types of targets were available. A field manual covering the use of the Sherman (FM 17–33, "The Tank Battalion, Light and Medium" of September 1942) described fighting enemy tanks, when necessary, as one of the many roles of the Sherman, with a page of text and four diagrams to tank-versus-tank action. This early armored doctrine was heavily influenced by the sweeping early successes of German blitzkrieg tactics. By the time M4s reached combat in significant numbers, battlefield demands for infantry support and tank-versus-tank action far outnumbered the occasional opportunities of rear-echelon attack.
United States doctrine held that the most critical anti-tank work stopping massed enemy tank attacks was primarily to be done by towed and self-propelled anti-tank guns, operated by "Tank Destroyer" battalions, with friendly tanks being used in support if possible. Speed was essential to bring the tank destroyers from the rear to destroy incoming tanks. This doctrine was rarely followed in combat, as it was found to be impractical. Commanders were reluctant to leave tank destroyers in reserve; if they were, it was also easier for an opposing armored force to achieve a breakthrough against an American tank battalion, which would not have all of its anti-tank weapons at the front during the beginning of any attack.
U.S. production history
The first production of the Sherman took place at the Lima Locomotive Works and was first used in 1941, with many early vehicles reserved for British use under Lend-Lease; the first production Sherman was given to the U.S. Army for evaluation, and the second tank of the British order went to London. Nicknamed Michael, probably after Michael Dewar, head of the British tank mission in the U.S., the tank was displayed in London and is now an exhibit at The Tank Museum, Bovington, UK.
In World War II, the U.S. Army ultimately fielded 16 armored divisions, along with 70 separate tank battalions, while the U.S. Marine Corps fielded six tank battalions. A third of all Army tank battalions, and all six Marine tank battalions, were deployed to the Pacific Theater of Operations (PTO). Before September 1942, President Franklin D. Roosevelt had announced a production program calling for 120,000 tanks for the Allied war effort. Although the American industrial complex was not affected by enemy aerial bombing or submarine warfare as was Japan, Germany and, to a lesser degree, Great Britain, an enormous amount of steel for tank production was diverted to the construction of warships and other naval vessels. Steel used in naval construction amounted to the equivalent of approximately 67,000 tanks; and consequently, only about 53,500 tanks were produced during 1942 and 1943.
The Army had seven main sub-designations for M4 variants during production: M4, M4A1, M4A2, M4A3, M4A4, M4A5, and M4A6. These designations did not necessarily indicate linear improvement; in that "M4A4" did not indicate it was better than "M4A3". These sub-types indicated standardized production variations, which were often manufactured concurrently at different locations. The sub-types differed mainly in engines, although the M4A1 differed from the other variants by its fully cast upper hull, with a distinctive rounded appearance. The M4A4 had a longer engine that required a longer hull and more track blocks, and thus the most distinguishing feature of the M4A4 was the wider longitudinal spacing between the bogies. "M4A5" was an administrative placeholder designation for Canadian Ram tank. The M4A6 had a radial diesel engine as well as the elongated chassis of the M4A4, but only 75 of these were ever produced.
Most Sherman sub-types ran on gasoline. The air-cooled Continental-produced Wright R-975 Whirlwind 9-cylinder radial gasoline engine in the M4 and M4A1 produced . The M4A3 used the liquid-cooled Ford GAA V8 gasoline engine, and the M4A4 used the liquid-cooled 30 cylinder Chrysler A57 multibank gasoline engine. There were also two diesel-engined variants. The M4A2 was powered by a pair of liquid-cooled GMC Detroit Diesel 6–71 two-stroke inline engines, that produced a total of , while the M4A6 used an RD-1820 (a redesigned Caterpillar D-200A air-cooled radial diesel engine, adapted from Wright Aeronautical's Wright R-1820 Cyclone 9 nine-cylinder radial aircraft engine.) that produced . A 24-volt electrical system was used in the M4. The M4A2 and M4A4 were mostly supplied to other Allied countries under Lend-Lease.