M4 Sherman

The M4 Sherman, officially Medium Tank, M4, was the most numerous battle tank used by the United States and some other Western Allies in World War II. It proved to be reliable and mobile. In spite of being outclassed by German medium and heavy tanks late in the war, the M4 Sherman was cheaper to produce and available in greater numbers.^[4] Thousands were distributed through the Lend-Lease program to the British Commonwealth and Soviet Union. The tank was named after the American Civil War General William Tecumseh Sherman by the British.

The M4 Sherman evolved from the interim M3 Medium Tank,^{[N 1]} which had its main armament in a side sponson mount. The M4 retained much of the previous mechanical design but put the main 75 mm gun in a fully traversing turret, with a gyrostabilizer which, while not enabling the crew to fire while on the move, did allow the gunner to aim while on the move, so that the tank could fire with reasonable accuracy as soon as it stopped.^[5] The designers stressed mechanical reliability, ease of production and maintenance, durability, standardization of parts and ammunition in a limited number of variants, and moderate size and weight. These factors combined with M4 Sherman's then-superior armor and armament outclassed German light and medium tanks of 1939–41. The M4 went on to be produced in large numbers. It spearheaded many offensives by the Western Allies after 1942. A similar vehicle was developed at the same time in Canada, the Ram tank, however greater Sherman production and availability meant that the Ram was never used in action.

When the M4 tank arrived in North Africa in 1942, it was superior to the lighter German long-barrel 50 mm-gunned Panzer III and short-barrel 75 mm-gunned Panzer IV. For this reason, the US Army believed the M4 would be adequate to win the war, and no pressure was exerted for further tank development. Logistical and transport restrictions, such as limitations imposed by roads, ports, and bridges, also complicated the introduction of a more capable but heavier tank.^{[6][N 2]} Tank destroyer battalions using vehicles built on the M4 hull and chassis, but with open-topped turrets and more potent high-velocity guns, also entered widespread use in the American army. Even by 1944, most M4 Shermans kept their dual purpose 75 mm M3.^[7] By 1944 and 1945, the M4 was inferior to German heavy tanks but was able to fight on with support from growing numbers of fighter-bombers and artillery pieces.^[8]

The relative ease of production allowed huge numbers of the M4 to be manufactured, and significant investment in tank recovery and repair units allowed disabled vehicles being repaired and returned to service. These factors combined to give the Americans numerical superiority in most battles, and many infantry divisions were provided with M4s and tank destroyers.^{[N 3]} During the Normandy campaign, German panzer divisions were rarely at full strength, and some U.S. infantry divisions had more fully tracked armored fighting vehicles than the depleted German panzer divisions.^[9] A M4A3E8 variant was introduced, with improved suspension and a high-velocity 76 mm gun as used on the tank destroyers.

Post World War II the Sherman, often in updated versions, saw combat in many conflicts, including the Korean War, Arab-Israeli Wars, and the Indo-Pakistani War of 1965.^[10]

U.S. design prototype

Cutaway Sherman showing transmission and driver's seat.

The U.S. Army Ordnance Department designed the Medium Tank M4 as a replacement for the Medium Tank M3. 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 tried by the British in Africa against early German tanks, 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.

Detailed design characteristics for the M4 were submitted by the Ordnance Department on 31 August 1940, but development of a prototype was delayed while the final 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 became the Sherman.^[11]

The Sherman's reliability resulted from many 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 goals were to produce a fast, dependable medium tank able to support infantry, provide breakthrough striking capacity, and defeat any tank then in use by the Axis nations, though it would later fall short against the much heavier tanks developed by Germany.

The T6 prototype was completed 2 September 1941. Unlike later M4s, the hull was cast and had a side hatch, which was eliminated from production models. The T6 was standardized as the M4 and production began in October.^[12]

Doctrine

A Sherman DD tank of 13th/18th Royal Hussars in action against German troops using crashed Horsa gliders as cover near Ranville, Normandy, 10 June 1944.

As the United States approached entry in World War II, armored employment was doctrinally governed by Field Manual 100–5, Operations (published May 1941, the month following selection of the M4 tank's final design). That field manual stated:

The armored division is organized primarily to perform missions that require great mobility and firepower. It is given decisive missions. It is capable of engaging in all forms of combat, but its primary role is in offensive operations against hostile rear areas.^[13]

The M4 was, therefore, not originally intended as an infantry support tank; in fact, FM 100-5 specifically stated the opposite. It placed tanks in the "striking echelon" of the armored division, and placed the infantry in the "support echelon". The field manual covering the use of the Sherman (FM 17–33, "The Tank Battalion, Light and Medium" of September 1942) devoted one page of text and four diagrams to tank-versus-tank action, out of 142 pages.^[14] This early armored doctrine was heavily influenced by the sweeping early war 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 exploitation.

United States doctrine held that anti-tank work was primarily to be done by anti-tank guns.^[15] Speed was essential in order to bring the tank destroyers from the rear to destroy incoming tanks. This doctrine was not entirely followed in practice, as it would create an interval of vulnerability in the armored battalion until tank destroyers moved to the front. This made it harder for an armored force to achieve a breakthrough against enemy armored forces. 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.^[16] The United States doctrine was less relevant in the Pacific where tank-versus-tank battles were less common and where the lighter Japanese tanks were considerably outmatched by the M4.

U.S. production history

M4A1 (76)W Sherman with cast hull

M4 and M4A1 (shown), the first Shermans, share the inverted U backplate and inherited their engine and exhaust system from the earlier M3 Medium Tank.

This M4A4 has extra armor plates in front of crew hatches.

The first production began with the Lima Locomotive Works on the assembly line set for tanks for British use. The first production Sherman was given over to the US Army for evaluation and it was the second tank of the British order that went to London. Named Michael probably after Michael Dewar, head of the British tank mission in the U.S., it was displayed in London and is now an exhibit at Bovington Tank Museum.^[17][18]

In World War II, the U.S. Army ultimately fielded 16 armored divisions, along with 70 independent tank battalions, while the U.S. Marine Corps fielded six independent Sherman tank battalions. A third of all Army tank battalions, and all six Marine tank battalions, were deployed to the Pacific Theater of Operations (PTO).^[19] Prior to September 1942, President Franklin D. Roosevelt had announced a production program calling for 120,000 tanks for the Allied war effort, which would have created 61 armored divisions. Although the American industrial complex was not affected by enemy aerial bombing nor submarine warfare as was Japan, Germany and, to a lesser degree, Great Britain, an enormous amount of steel for tank production had been diverted to the construction of warships and other naval vessels.^[20] 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.^[21]

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. For example, A4 did not indicate it was better than an A3. These sub-types indicated standardized production variations, which were in fact 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 system that required a longer hull, a longer suspension system, and more track blocks, and thus the most distinguishing feature of the A4 was the wider spacing between the bogies. M4A5 was an administrative placeholder designation for Canadian production. The M4A6 had an elongated chassis and additional armor, but fewer than 100 of these were ever produced.

While most Shermans ran on gasoline, the M4A2 and M4A6 had diesel engines. The M4A2 with a pair of GMC 6–71 straight six engines,^[22] the M4A6 a Caterpillar RD1820 radial.^[23] These, plus the M4A4, which used the Chrysler A57 multibank engine, were mostly supplied to other Allied countries under Lend-Lease.^[24] "M4" can refer specifically to the initial sub-type with its Continental radial engine (R-975), or generically, to the entire family of seven Sherman sub-types, depending on context. Many details of production, shape, strength and performance improved while in production, without a change to the tank's basic model number. These included more durable suspension units, safer "wet" (W) ammunition stowage, and stronger armor arrangements, such as the M4 Composite, which had a cast front hull section mated to a welded rear hull. British nomenclature differed from that employed by the U.S.

A 24-volt electrical system was used in the M4.^[2]

A 76 mm M1 gun gun equipped Sherman

Early Shermans mounted a 75 mm medium-velocity general-purpose gun. Although Ordnance began work on the Medium Tank T20 as a Sherman replacement, ultimately the Army decided to minimize production disruption by incorporating elements of other tank designs into the Sherman. Later M4A1, M4A2, and M4A3 models received the larger T23 turret with a high-velocity 76 mm M1 gun, which reduced the number of high explosive and smoke rounds carried and increased the number of anti-tank rounds. Later, the M4 and M4A3 were factory-produced with a 105 mm howitzer and a distinctive mantlet on the turret which surrounded the main gun. The first standard-production 76 mm gun Sherman was an M4A1, accepted in January 1944, and a number were quickly sent to the Armored Divisions in Europe for the upcoming Operation Cobra. The first standard-production 105 mm howitzer Sherman was an M4 accepted in February 1944.

In June–July 1944, the Army accepted a limited run of 254 M4A3E2 Jumbo Shermans, which had very thick armor for the front (glacis) plate, sloped somewhat more steeply to eliminate the forward hull entryway bulges on the upper portion of the original glacis plate, and the 75 mm gun in a new, heavier T23-style turret, in order to assault fortifications. The M4A3 was the first to be factory-produced with the option of the horizontal volute spring suspension (HVSS) system, with wider tracks to distribute weight, and the smooth ride of the HVSS. Its experimental E8 designation led to the nickname Easy Eight for Shermans so equipped. Both the Americans and the British developed a wide array of special attachments for the Sherman, although few saw combat, remaining experimental. Those that saw action included the bulldozer blade for the Sherman dozer tanks, Duplex Drive for amphibious Sherman tanks, R3 flamethrower for Zippo flame tanks, and the T34 60-tube Calliope 4.5" rocket launcher mountable atop the Sherman's turret. The British variants (DDs and mine flails) formed part of the group of specialized vehicles collectively known as "Hobart's Funnies" (after Percy Hobart, commander of the 79th Armoured Division).

The M4 Sherman's basic chassis was used for all the sundry roles of a modern mechanized force: roughly 50,000 Sherman tanks, plus thousands more derivative vehicles under different model numbers. These included the M10 Wolverine (17pdr SP Achilles, in British service) and M36 tank destroyers; M7B1, M12, M40, and M43 self-propelled artillery; the M32 and M74 "tow truck"-style recovery tanks with winches, booms, and an 81 mm mortar for smoke screens; and the M34 (from M32B1) and M35 (from M10A1) artillery prime movers.

M4A4 Cutaway: 1 - Lifting ring, 2 - Ventilator, 3 - Turret hatch, 4 – Periscope, 5 – Turret hatch race, 6 – Turret seat, 7 – Gunner's seat, 8 – Turret seat, 9 – Turret, 10 – Air cleaner, 11 – Radiator filler cover, 12 – Air cleaner manifold, 13 – Power unit, 14 – Exhaust pipe, 15 – Track idler, 16 – Single water pump, 17 – Radiator, 18 – Generator, 19 – Rear propeller shaft, 20 – Turret basket, 21 – Slip ring, 22 – Front propeller shaft, 23 – Suspension bogie, 24 – Transmission, 25 – Main drive sprocket, 26 – Driver's seat, 27 – Machine gunner's seat, 28 – 75 mm gun, 29 – Drivers hatch, 30 – M1919A4 machine gun.

Service history

The first Sherman in U.S. service, the M4A1, appeared in the North Africa Campaign. Here one of the 7th Army lands at Red Beach 2 on July 10, 1943 during the Allied invasion of Sicily.

M4A3E8 participating in a World War II victory parade has front armor flat against both crew hatches, based on that of the "Jumbo" MAA3E2s.

Allocation

During World War II, approximately 19,247 Shermans were issued to the US Army and about 1,114 to the US Marine Corps.^[28] The U.S. also supplied 17,184 to Great Britain (some of which in turn went to the Canadians and the Free Poles), while the Soviet Union received 4,102^[29] and an estimated 812 were transferred to China.^[30] These numbers were distributed further to the respective countries' allied nations.

The U.S. Marine Corps used the diesel M4A2 and gasoline-powered M4A3 in the Pacific. However, the Chief of the Army's Armored Force, Lt. Gen. Jacob L. Devers, ordered no diesel-engined Shermans be used by the Army outside the Zone of Interior (the continental U.S.). The Army used all types for either training or testing within the United States but intended the M4A2 and M4A4 (with the A57 Multibank engine) to be the primary Lend-Lease exports.

First combat

The Sherman was being issued in small numbers for familiarization to U.S. armored divisions when there was a turn of events in the Western Desert campaign. Axis forces had taken Tobruk and were advancing into Egypt and the Britain's supply line through the Suez Canal was threatened. The US considered collecting all Shermans together so as to be able to send the 2nd Armored Division under Patton to reinforce Egypt, but delivering the Shermans directly to the British was quicker and 300 had arrived there by September 1942.^[17]

The M4A1 Sherman first saw combat at the Second Battle of El Alamein in October 1942 with the British 8th Army. The first U.S. Shermans in battle were M4A1s in Operation Torch the next month. At this time, Shermans successfully engaged German Panzer IIIs and Panzer IVs at ranges up to 2,000 yards (1,800 m).^[31] Additional M4s and M4A1s replaced M3s in U.S. tank battalions over the course of the North African campaign.

The M4 and M4A1 were the main types in U.S. units until late 1944, when the Army began replacing them with the preferred M4A3 with its more powerful 500 hp (370 kW) engine and 76 mm gun. Some M4s and M4A1s continued in U.S. service for the rest of the war. The first Sherman to enter combat with the 76 mm gun in July 1944 was the M4A1, closely followed by the M4A3. By the end of the war, half the U.S. Army Shermans in Europe had the 76 mm gun. The first HVSS Sherman to see combat was the M4A3E8(76)W in December 1944.

Pacific Theater

As part of Operation Dexterity, a Sherman advances through a tropical rain forest on New Britain, in the South-West Pacific.

While combat in the European Theater of Operations (ETO) consisted of high-profile armored warfare, the mainly naval nature of the Pacific Theater of Operations (PTO) relegated it to secondary status for both the Allies and the Japanese. While the US Army fielded 16 armored divisions and 70 independent tank battalions during the war, only a third of the battalions and none of the divisions were deployed to the Pacific Theater.^[32] The Imperial Japanese Army (IJA) deployed only their 2nd Tank Division to the Pacific during the war.^[33] Armor from both sides mostly operated in jungle terrain that was poorly suited for armored warfare. For this type of terrain, the Japanese and the Allies found light tanks easier to transport and employ.^[34]

During the early stages of combat in the Pacific, specifically the Guadalcanal Campaign, the U.S. Marine Corps' M2A4 light tank fought against the equally matched Type 95 Ha-Go light tank; both were armed with a 37 mm main gun, however the M2 (produced in 1940) was newer by five years.^[35] By 1943, the IJA still used the Type 95 and Type 97 Chi-Ha medium tanks, while Allied forces were quickly replacing their light tanks with 75 mm-armed M4s.^[36] The Chinese in India received 100 M4 Shermans and used them to great effect in the subsequent 1943 and 1944 offensives.

To counter the Sherman,^[37] the Japanese developed the Type 3 Chi-Nu and the heavier Type 4 Chi-To; both tanks were armed with 75 mm guns, albeit of different type. Only 166 Type-3's and two Type-4's were built and none saw combat; they were saved for the defense of the Japanese homeland, leaving 1930s vintage light and medium tanks to do battle against 1940s built medium Allied armor.

During these latter years of the war, General Purpose High Explosive (HE) ammunition was preferred, because armor-piercing rounds, which had been designed for penetrating thicker steel, often went through the thin armor of the Type 95 Ha-Go (the most commonly encountered Japanese tank) and out the other side without stopping. Although the high-velocity guns of the tank destroyers were useful for penetrating fortifications, M4s armed with flamethrowers were often deployed, as direct fire seldom destroyed Japanese fortifications.^[38][39]

Post–World War II

Last type in US service: M4A3E8 Sherman used as artillery in firing position during the Korean War.

After World War II, the U.S. kept the M4A3E8 Easy Eight in service with either the 76 mm gun or a 105 mm M4 howitzer, being the most advanced type of Sherman that the US developed. The Sherman remained a common U.S. tank in the Korean War. Despite no longer being the primary U.S. tank, it fought alongside the M26 Pershing and M46 Patton. The M4A3E8 Sherman and T-34-85 were comparable and could destroy each other when hit, although the use of High Velocity Armor Piercing shells gave the Sherman a firepower advantage. The Sherman had better optics, which gave it a better chance of scoring a first round hit.^[40] The M4A3E8 Sherman, using 76 mm HVAP ammunition, destroyed a total of 41 enemy tanks from July-November 1950. The lighter M4A3E8 tank became the preferred US tank in the later phases of the Korean conflict, due to the mechanical reliability of the M4, its ease of maintenance, and its driveability compared to the M26 tank.^[41]

The U.S. Army replaced them with M46 Pattons, an improved M26, during the 1950s. The U.S. continued to transfer Shermans to its allies, which contributed to widespread foreign use.

The Israeli Army used imported M4A1 Shermans during the 1956 Suez Crisis. About 300 Shermans were upgraded with the long high-velocity 75 mm gun CN 75-50 of the AMX-13 and were designated Sherman M-50 (a.k.a. Super Sherman) by the Israelis. Before the Six Day War in 1967, the Israeli Army upgraded about 180 M4 Shermans with the French 105 mm Modèle F1 gun, re-engined them with Cummins engines and designated the upgraded tank Sherman M-51 (a.k.a. Super Sherman or ISherman). The ISherman tanks, fighting alongside the 105 mm Centurion Sh'ot Kal and M48 Patton tanks, were able to defeat the T-34/85, T-54/55/62 series, and IS-3 tanks used by the Egyptian and Syrian forces in the 1967 Six Day War.^[42]

Armament

The gun on the original M4 was the short-barreled medium-velocity 75 mm M3 gun. When it first saw combat in North Africa in late 1942 against the Panzer III and Panzer IV, the Sherman's gun could penetrate the armor of these tanks within 1,000 yd (910 m). U.S. Army Intelligence discounted the arrival of the Tiger I in late 1942 and the Panther tank in 1943, predicting the Panther to be a heavy tank like the Tiger, and doubted they would produce many. There were also reports of relatively small caliber British QF 6 pdr (57 mm) guns being able to destroy the Tiger. However, this was only happening at very close ranges and against the thinner side armor. Due to their misconceptions related to this, and also due to tests that seemed to prove that the 76 mm gun was able to destroy both the Tiger and the Panther, the leadership of Army Ground Forces were not especially concerned by the Tiger. The tests of the 76 mm were later ruled inaccurate, with Eisenhower even remarking he was wrongly told by Ordnance the 76 mm could knock out any German tank. The Army also failed to anticipate the Germans would make the Panther the standard tank of their panzer divisions in 1944, supported by some Tigers.^[43]

Despite the Bureau of Ordnance development of new 76 mm and 90 mm anti-tank guns, the Army Ground Forces rejected their deployment on U.S. tanks as unnecessary. Even in 1943, most German armored fighting vehicles (later models of the Panzer IV, StuG III, and Marder III) mounted the 7.5 cm KwK 40. As a result, even weakly armored light German tank destroyers such as the Marder III, which was meant to be a stop-gap measure to fight Soviet tanks in 1942, could destroy Shermans from a distance. The disparity in firepower between the German armored fighting vehicles of 1943 and the 75 mm-armed M4 was the impetus to begin production of 76 mm-armed M4s in April 1944.^[44] However, transfer of the tanks to the front started slowly, and most tanks still had 75 mm M3 guns, even by Operation Cobra in July 1944.^[45]

The M4A2 76 mm gun could penetrate some 98 mm (3.9 in) of unsloped face hardened armor plate at 2,000 meters (2,200 yd) using M62 APCBC ammunition, about twice the average tank engagement range noted by the Canadians. This was easily enough to reliably penetrate a Panzer IV's glacis, which offered a maximum of about 87 millimetres (3.4 in) of protection. However, the 76 mm was not powerful enough against the upper glacis of a Panther. Due to its 55 degree angle, the Panther's 80 millimetres (3.1 in) upper glacis had a line of sight thickness of 140 mm (5.51 in) with actual effectiveness being even greater. Utilizing standard M79 armor piercing shot, a M4 might only knock out a Panther frontally from point-blank ranges. Therefore, Shermans had to aim for the Panther's weaker turret and mantlet. A 76 mm M4A2 armed Sherman could penetrate the upper frontal hull superstructure of a Tiger I heavy tank from 400 meters (440 yd); although this lessened the gap between the tanks, the Tiger I was capable of knocking a M4 out frontally from over 2,000 meters (2,200 yd).^[46] Sherman crews also had concerns about firing from longer ranges, as the Sherman's high-flash powder made their shots easy to spot. Their gun sights were fixed magnification, while German tanks had multiple magnification settings. Sherman gunners did have the use of a secondary sight which allowed them a larger field of view over their German counterparts. However this advantage was mostly useful in close range situations due to lack of magnification. In summer 1944, after breaking out of the bocage and moving into open country, U.S. tank units which engaged at longer ranges from German defensive positions sometimes took 50% casualties before spotting where the fire was coming from.^[47]

The Sherman was first equipped with the L/40 75 mm M3 Gun, which could penetrate 87 millimetres (3.4 in) of unsloped rolled homogeneous armor at 100 meters (110 yd) and 70 millimetres (2.8 in) at 1,000 meters (1,100 yd) firing the usual M61 round.^[48] The average combat range noted by the Americans for tank vs. tank action was 800 meters (870 yd) to 900 meters (980 yd). Conditions later in the war necessitated up-gunning to the 76 mm L/55 M1A2, which could penetrate 143 millimetres (5.6 in) of unsloped rolled homogeneous armor at 100 meters (110 yd) and 97 millimetres (3.8 in) at 1,000 meters (1,100 yd) using the usual M79 round.^[49] The M1A2 helped to equalize the Sherman and the Panzer IV in terms of firepower, although the M4 still needed improved ammunition in the form of tungsten rounds to equal the Panther, with its much more powerful 7.5 cm KwK 42 gun. The KwK 42 could penetrate 185 millimetres (7.3 in) at 100 meters (110 yd)^[50] and 149 millimetres (5.9 in)^[51] at 1,000 meters (1,100 yd) using the usual PzGr.39/42 round. The British-developed Sherman Firefly was an M4 re-gunned with their own, 3-inch (76.2 mm) caliber QF 17 pounder anti-tank gun. The 17 pdr was a 76 mm gun and had a 55 caliber barrel but used a much bigger charge which allowed it to penetrate 140 millimetres (5.5 in) (of RHA sloped at 30 degrees) at 100 meters (110 yd) and 120 millimetres (4.7 in) at 1,000 meters (1,100 yd) using APC Mk.IV shot.^[52] This gun allowed the Firefly a firepower equal to that of the Panther, especially with APDS, although the muzzle flash due to unburnt powder from the increased charge left crews momentarily blinded after firing.^[9]

The tank destroyer doctrine

General Lesley J. McNair was head of Army Ground Forces. McNair, an artilleryman, championed the tank destroyer (TD) within the U.S. Armored Forces. Tanks were to support the infantry, exploit breakthroughs, and avoid tank-to-tank battles. Enemy tanks were to be engaged by the tank destroyer force, composed of a mix of self-propelled tank destroyers and towed anti-tank guns. U.S. tank destroyers, called "gun motor carriages" (as were any US Army self-propelled armored vehicles mounting an artillery piece of heavy caliber) were similar to tanks but were lightly armored with open-topped turrets. The tank destroyers were supposed to be faster and carry a more powerful anti-tank gun than tanks; armor was sacrificed for speed. The tank destroyer doctrine played a large role in the lack of urgency in improving the firepower of the M4 Sherman, as the emphasis was on its role as infantry support.^[53]

McNair approved the 76 mm upgrade to the M4 Sherman and production of the 90 mm gun-armed M36 tank destroyer, but he staunchly opposed development of the T26 and other proposed heavy tanks during the crucial period of 1943 because he saw no "battle need" for them.

In mid-1943, Lt. General Devers, commander of U.S. forces in the European Theater of Operations (ETO), asked for 250 T26s for use in the invasion of France. McNair refused. Devers appealed to General George Marshall, the Army Chief of Staff. Marshall summarily ordered the tanks to be provided to the ETO as soon as they could be produced. Soon after the Normandy invasion, General Dwight D. Eisenhower urgently requested heavy tanks (now designated M26 Pershing), but McNair's continued opposition delayed production. General Marshall intervened again and the tanks were eventually brought into production. However, only a few saw combat on February 25, 1945, too late to have any effect on the battlefield.^[54]

Gun development

This M4A2(76) HVSS shows the T23 turret with later 76 mm gun's muzzle brake. This one also has fenders, usually omitted on U.S. vehicles to ease maintenance.

When the 76 mm gun was first installed in the M4 turret, it was found to unbalance the turret, and the gun barrel was also thought to protrude too far forward, making it more difficult to transport and susceptible to hitting the ground on undulating terrain. Army Ordnance reduced the barrel length by 15 inches (380 mm) (from 57 calibers long to 52), which decreased performance by 10%. Mounting this gun in the original M4 turret proved to be problematic, and so the turret for the aborted T23 tank project was used instead for the definitive production version of the 76 mm M4 Shermans.^[55]

Although tests against armor plate suggested the new M4A2 76 mm gun would be adequate, testing against captured Panther tanks was never done. This would have shown the gun could penetrate the gun mantlet and possibly the glacis of the Panther only at point blank or very close ranges.^[56] In practice, this meant that despite both the Panther and Sherman being classed and produced as "medium tanks" by their respective forces, the Panther was basically invincible in frontal engagements against the Sherman at anything but point blank range. Once this was discovered, it was insisted that the superior mobility of the open-topped tank destroyers would obviate the deficiency in firepower; this assumption proved to be flawed as well, as most tank combat occurred in confined urban or bocage areas where mobility was highly limited and the light armor and lack of overhead cover of the tank destroyers was readily exploited by Panzerschreck- and Panzerfaust-armed infantry troops.

The 90 mm gun developed by U.S. Ordnance could not be easily installed on the M4 but was installed on the open-turreted M36 tank destroyer and was the main gun for the T26 tank project (which eventually became the M26 Pershing). An attempt to upgrade the M4 Sherman by installing the 90 mm T26 turret on a M4A3 hull in April 1944 was halted after realizing it could not go into production sooner than the T26 and would likely delay T26 development.^[57]

In testing prior to the invasion of Normandy, the new 76 mm gun on the M4 Sherman was found to have an undesirably large muzzle blast that kicked up dust from the ground and obscured vision for further firing. The addition of a muzzle brake solved this problem by directing the blast sideways. It also had a much weaker high-explosive shell than the existing 75 mm gun. Standard Army doctrine at the time emphasized the importance of the infantry support role of the tank, and the high-explosive round was considered more important. Hence the 76 mm M4 was not initially accepted by various US Armored Division commanders, even though a number had already been produced and were available. All of the US Army M4s deployed initially in Normandy in June 1944 had the 75 mm gun.^[58]

British Firefly in Namur, 1944

The British were more astute in their anticipation of the future development of German armor — beginning development of a 3-inch (76 mm) anti-tank gun even before its 57 mm predecessor entered service and planning for its use in tanks that would replace the M4. Out of expediency driven by delays in their new tank designs, they mounted this high-powered Ordnance QF 17-pounder gun in a standard 75 mm M4 Sherman turret. This conversion became the Sherman Firefly. The 17 pounder still could not penetrate the glacis plate of the Panther but it could penetrate the Panther's gun mantlet at over 2,500 yards (2,300 m);^[59][60] moreover it was estimated it could penetrate the Tiger I's front from 1,900 yards (1,700 m) well before the Tiger would penetrate the Sherman's glacis, which at 30 degrees was invulnerable to the 8.8 cm KwK 36.^[61][62] Late in 1944, the British began to produce tungsten-cored sabot rounds for the 17 pounder gun, which could readily penetrate the armor of even the Tiger II, but these rounds were not as accurate as standard rounds and not generally available.

In late 1943, the British offered the 17 pounder to the U.S. Army for use in their M4 tanks. General Devers insisted on comparison tests between the 17 pounder and the U.S. 90 mm gun (even though the 17 pounder could be mounted in a standard M4 turret while the 90 mm gun needed a new turret). The tests were finally done on March 25 and May 23, 1944; they seemed to show that the 90 mm gun was equal to or better than the 17 pounder. By then, production of the 76 mm M4 and the 90 mm M36 tank destroyer were both underway and U.S. Army interest in the 17 pounder waned.

Fighting against Panther tanks in Normandy quickly demonstrated the need for better anti-tank firepower, and the 76 mm M4s were deployed to First Army units in July 1944. General George S. Patton's Third Army were initially issued 75 mm M4s and accepted 76 mm M4 Shermans only after the Battle of Arracourt against Panther tanks in late September 1944.^[63]

High-Velocity Armor Piercing (HVAP) ammunition, standardized as M93, became available in August 1944 for the 76 mm gun. The projectile contained a tungsten core penetrator surrounded by a lightweight aluminum body, which gave it a higher velocity and more penetrating power. The increased penetration of HVAP allowed the 76 mm gun M1 to match the Panther's 7.5 cm KwK 42 APCR shot. ^[64] However, its performance was heavily degraded by sloped armor such as the Panther's glacis, which was immune to HVAP rounds necessitating shots to be aimed at the mantlet and turret front.^[64] Because of tungsten shortages, HVAP rounds were constantly in short supply. Priority was given to U.S. tank destroyer units; most Shermans carried only a few rounds and some units never received any.^[65]

After the heavy tank losses of the Battle of the Bulge, in January 1945, General Eisenhower asked that no more 75 mm M4s be sent to Europe: only 76 mm M4s were wanted.^[66]

Interest in mounting the British 17-pounder in U.S. Shermans flared anew. In February 1945, the U.S. Army began sending 75 mm M4s to England for conversion to the 17-pounder. Approximately 100 conversions were completed by the beginning of May. By then, the end of the war in Europe was clearly in sight, and the U.S. Army decided the logistic difficulties of adding a new ammunition caliber to the supply train was not warranted. None of the converted 17-pounder M4s were deployed by the U.S., and it is unclear what happened to most of them, although some were given to the British as part of Lend-Lease.^[67]

The higher-velocity 76 mm M1 gun gave Shermans anti-tank firepower at least equal to most of the German vehicles they encountered, particularly the Panzer IV, and StuG III. However, with a regular AP (Armor Piercing shot) ammunition (M79), the 76 mm might knock out a Panther only at point blank range with a shot to the upper glacis, at close range with a shot to its mantlet, or at long range with a shot its flank. At long range, the Sherman was outmatched by the Panther's 75 mm gun, which could easily penetrate the Sherman's armor from all angles. This, and the US Army's usual offensive tactical situation, contributed to losses suffered by the U.S. Army in Europe.^[68]

The M4 was criticized by its crews for inability to pivot turn (turn in place), limiting its usefulness in urban warfare against pivot-turning Panthers.^[69] This deficiency was partially compensated by the faster traverse of its turret.

Miscellaneous

A USMC M4A3 uses its flame thrower armament during the Battle of Iwo Jima.

The Sherman was one of the first widely produced tanks to feature a gyroscopic stabilized gun and sight. The stabilization was only in the vertical plane, as the mechanism could not slew the turret. The stabilizer was sufficient to keep the gun within 1/8th of a degree, or 2 mils while crossing moderately rough terrain at 15 miles per hour (24 km/h). This gave a hit probability of 70% on enemy tanks at ranges of 300 yards (270 m) to 1,200 yards (1,100 m).^[70] The utility of the stabilization is debatable, with some saying it was useful for its intended purpose, others only for using the sights for stabilized viewing on the move.^[71] Some operators disabled the stabilizer.

The 75 mm gun also had an effective canister round that functioned as a large shotgun. In the close fighting of the French bocage, the 2nd Armored Division tanks used Culin Hedgerow Cutters fitted to their tanks to push three tanks together through a hedgerow. The flank tanks would clear the back of the hedgerow on their side with canister rounds while the center tank would engage and suppress known or suspected enemy positions on the next hedgerow. This approach permitted surprisingly fast progress through the very tough and well-defended hedgerows in Normandy. Over 500 sets of these were fitted to US armored vehicles, and many fitted to various British tanks (where they were called "Prongs").

The 75 mm gun had a white phosphorus shell originally intended for use as an artillery marker to help with targeting. M4 tank crews discovered that the shell could also be used against the Tiger and Panther—when the burning white phosphorus adhered to the German tanks, their excellent optics would be blinded and the acrid smoke would get sucked inside the vehicle, making it difficult or impossible for the crew to breathe. This, and the fear of the fire spreading inside the tank, would sometimes cause the crew to abandon the tank.^[72] There were several recorded instances where white phosphorus shells defeated German tanks in this fashion.^[73]

A variant of the M4 Sherman was armed with the 105 mm M4 howitzer, which provided even more powerful high-explosive armament. This variant was employed in six-vehicle "assault gun" platoons in armored battalions to provide close fire support and smoke. The 105 mm-armed variants were of limited use against enemy tanks due to the poor anti-armor performance of the howitzer, which was not intended to fight other tanks, though a high explosive anti-tank (HEAT) round for the 105 mm howitzer was available for self-defense.

Armor

This early 75 mm gun turret shows the single hatch — note the additional rectangular external (welded on) appliqué armor patch reinforcing the ammunition bin protection on the hull side.

The steel frontal turret armor of the M4 ranged from 64–76 mm (2.52–2.99 in).^[74] The M4's gun mantlet was also protected by 76 mm (2.99 in) of armor^[74] sloped at 30 degrees from the vertical,^[75] The turret side armor was 50 mm (1.97 in) a 5-degree angle^[75] while the rear was 64 mm (2.52 in) at a 90-degree angle and the turret roof was 25 mm (0.98 in) thick.^[76] The frontal hull armor was 51 mm (2.01 in) thick.^[74][76] The Sherman's upper hull was angled at 56 degrees, while the lower half of the hull was curved.^[76] The hull sides were 38–45 mm (1.50–1.77 in) thick,^[75][77] and vertical.^[76] The hull rear—which protected and was offset from the rear radiator on some versions—was 38 mm (1.50 in) of steel ranging from 0 to 22 degrees to the vertical, depending on the variant.^[78] The hull roof was 25 mm (0.98 in).^[76]

Upgraded Shermans with the T23 turret and new 76 mm gun had upgraded frontal hull armor that was 64 mm (2.52 in) thick and sloped at 47 degrees from the vertical, or in the case of the M4A1(76)W, curved from 37 to 55 degrees from the vertical, with the large majority of the plate sitting closer to a 55° angle.^[78] The lower hull was 51–108 mm (2.01–4.25 in) thick and sloped at 56 to 0 degrees from the vertical, respectively.^[49] The turret was 64 mm (2.52 in) thick, sitting at 40 to 45 degrees from the vertical.^[78] The frontal turret was further protected by an unsloped 89 mm (3.50 in) gun mantlet.^[49] The turret sides were 64 mm (2.52 in) ranging from 0 to 13 degrees to the vertical, while the turret rear was unsloped.^[49]

The armor of the M4 was effective against most early war anti-tank weapons,^[74] but needed a compound angle to resist later German tank and anti-tank guns. Early versions had unfortunate shot traps, locations where the effect of slope was greatly reduced, located just in front of the driver and assistant driver. The KwK 40 7.5 cm L/48 tank gun that armed late war versions of the Panzer IV could penetrate a Sherman's armor up to a range of 1,370^[79]–1,500 meters, and larger guns could penetrate past 2,000 meters (2,200 yd).^[80] Regardless of this vulnerability, historian John Buckley has stated the M4 was "moderately superior" to the relatively small but older Panzer IV. A Waffenamt-Prüfwesen 1 report estimated ^[81] that with the M4 angled 30 degrees sidewards, the Sherman's glacis was impervious to the Tiger's 8.8 cm KwK 36 L/56^[82] and that the Panther with its 7.5 cm KwK 42 L/70 would have to close in to 100 meters (110 yd) in the same situation.^[83] Although the later-model medium and heavy tanks were greatly feared, Buckley opined "The vast majority of German tanks encountered in Normandy were either inferior, or at least, merely equal to the Sherman."^[84]

Progressively thicker armor was added to hull front and turret mantlet in various improved models. Many had an additional rectangular patch on each side protecting ammunition stowage, others had an additional slanted plate in front of each front crew hatch. Field improvisations included placing sandbags, spare track links, concrete, wire mesh, or even wood for increased protection against shaped-charge rounds. While mounting sandbags around a tank had little effect against high-velocity anti-tank gunfire it was thought to provide standoff protection against HEAT weapons, primarily the German Panzerfaust anti-tank grenade launcher and Panzerschreck anti-tank rocket launcher. By 1945, it was rare to see a Sherman without any field improvisations. In the only study known to have been done to test the use of sandbags, on March 9, 1945, officers of the 1st Armored Group tested standard Panzerfaust 60s against sandbagged M4s; shots against the side blew away the sandbags and still penetrated the side armor, whereas shots fired at an angle against the front plate blew away some of the sandbags but failed to penetrate the armor. Earlier, in the summer of 1944, General Patton, informed by his ordnance officers that sandbags were useless and that the machines' chassis suffered from the extra weight, had forbidden the use of sandbags. Following the clamor for better armor and firepower after the losses of the Battle of the Bulge, Patton ordered extra armor plates salvaged from knocked-out American and German tanks welded to the front hulls of tanks of his command. Approximately 36 of these up-armored M4s were supplied to each of the armored divisions of the Third Army in the spring of 1945.^[85]

M4A3E2 Sherman Jumbo. Some units replaced the original 75 mm gun with a 76 mm gun.

The M4A3E2 Sherman Jumbo variant had frontal armor almost twice as effective as the Tiger I. Its 102 millimetres (4.0 in) thick glacis was angled at 47 degrees from vertical, a "higher" angle than the original welded-design Sherman glacis was built with, which resulted in a glacis 150 millimetres (5.9 in) LOS thick and over 180 millimetres (7.1 in) effective,^[86] proof against all German tank guns. The higher angle of the thicker E2 Jumbo glacis allowed the forward crew hatchways to no longer require the forward protrusions through the shallower-angled glacis which the original M4 welded and cast hull designs possessed, sponson sides uparmored to 76.2 millimetres (3.00 in), a significantly thicker transmission casing, a thicker welded mantlet and a thicker cast turret for the main gun. Intended for the assault to break out of the Normandy beachhead, it was initially armed with the 75 mm although the gun mount was designed for the 76 mm allowing the 76 mm to be easily mounted in the field. It arrived in Europe in the Fall of 1944 and was employed throughout the remainder of the fighting. They were highly successful and 254 of them were built.^[87] The later "Easy Eight" M4A3E8 Shermans also standardized the Jumbo Sherman's glacis design, and also possessed no protruding forward hatchways.

The M4 had a hatch on the hull bottom to dispose of spent shell casings and to provide an emergency escape route. In the Pacific, Marines used this Sherman feature in reverse to recover wounded infantry under fire. Combat experience indicated the single hatch in the three-man turret to be inadequate for timely evacuation, so Ordnance added a loader's hatch beside the commander's. Later M4s also received redesigned hull hatches for better egress.

The 1943 modernization program for older tanks added welded patches of appliqué armor to the sides of the turret and hull. This Sherman also sports a Culin hedgerow cutter, a 1944 field improvisation for breaking through the thick hedgerows of the Normandy bocage.

Research conducted by the British No. 2 Operational Research Section, after the Normandy campaign, concluded that a Sherman would be set alight 82% of the time following an average of 1.89 penetrations of the tank's armor; in comparison they also concluded the Panzer IV would catch fire 80% of the time following an average of 1.5 penetrations, the Panther would light 63% of the time following 3.24 penetrations, and the Tiger would catch fire 80% of the time following 3.25 penetrations.^[88] John Buckley, using a case study of the British 8th and 29th Armoured Brigades found that of their 166 Shermans knocked out in combat during the Normandy campaign, 94 were burnt out; 56.6%. Buckley also notes that an American survey carried out concluded that 65% of tanks burnt out after being penetrated.^[89] United States Army research proved that the major reason for this was the stowage of main gun ammunition in the sponsons above the tracks. A U.S. Army study in 1945 concluded that only 10–15 percent of wet-stowage Shermans burned when penetrated, compared to 60–80 percent of the older dry-stowage Shermans.^[90]

At first a partial remedy to ammunition fires in the M4 was found by welding 1-inch-thick (25 mm) appliqué armor plates to the sponson sides over the ammunition stowage bins, though there was doubt that these had any effect. Later models moved ammunition stowage to the hull floor, with additional water jackets surrounding the main gun ammunition stowage. The practice, known as wet stowage, reduced the chance of fire after a hit to about 15%.^[91] The Sherman gained grim nicknames like "Tommycooker" (by the Germans, who referred to British soldiers as "Tommies"; a tommy cooker was a World War I-era trench stove). The British took to calling it the "Ronson"^[92] Fuel fires occasionally occurred, but such fires were far less common and less deadly than ammunition fires.^[90] In many cases the fuel tank of the Sherman was found intact after a fire. Tankers described "fierce, blinding jets of flame," which is inconsistent with gasoline-related fires.^[89]

The armor of the Sherman and Panther were compared in a report to General Eisenhower at SHAEF, among anecdotes reported by US servicemen:

I have actually seen ricochets go through an M4 at 3000 yards.... I have seen HEAT fired from a 105mm Howitzer at a Mark V [Panther] at 400 yards. The track was hit and damaged, and a direct hit exploded on the turret which only chipped the paint.^[93]

Mobility

Vertical volute springs of Stuart tank with similar suspension system.

In its initial specifications for the replacement tank for the M3 Medium Tank, the U.S. Army restricted the Sherman's height, width, and weight so that it could be transported via typical bridges, roads, railroads and landing craft without special accommodation. This greatly aided the strategic, logistical, and tactical flexibility and mobility of all Allied armored forces using the Sherman.

The Sherman had good speed both on- and off-road. Off-road performance varied. In the desert, the Sherman's rubber-block tracks performed well. In the confined, hilly terrain of Italy, the Sherman could often cross terrain that some German tanks could not.

Albert Speer recounted in his autobiography Inside the Third Reich

On the southwestern front (Italy) reports on the cross country mobility of the Sherman have been very favorable. The Sherman climbs mountains our tank experts consider inaccessible to tanks. One great advantage is that the Sherman has a very powerful motor in proportion to its weight. Its cross-country mobility on level ground is, as the 26th Panzer Division reports, definitely superior to that of our tanks^[94]

However, while this may have held true compared with the first generation German tanks such as the Panzer III and Panzer IV, comparative testing with the second generation German tanks (Panther and Tiger) conducted by the Germans at their Kummersdorf testing facility, as well as by the U.S. 2nd Armored Division, proved otherwise, possibly hinting at the complex overlapped and interleaved Schachtellaufwerk road wheel system used on the Panther and Tiger I, and the simpler overlapping all-steel, internally sprung road wheels of the heavier King Tiger German tanks.

Lieutenant Colonel Wilson M. Hawkins of the 2nd AD wrote the following comparing the US M4 Sherman and German Panther in a report to Allied headquarters:

It has been claimed that our tank is the more maneuverable. In recent tests we put a captured German Mark V [Panther] against all models of our own. The German tank was the faster, both across country and on the highway and could make sharper turns. It was also the better hill climber.^[95]

This was backed up in an interview with Technical Sergeant Willard D. May of the 2nd AD who commented:

I have taken instructions on the Mark V [Panther] and have found, first, it is easily as maneuverable as the Sherman; second the flotation (ability to avoid bogging down) exceeds that of the Sherman.^[95]

Staff Sergeant and Tank Platoon Sergeant Charles A. Carden completes the comparison in his report:

The Mark V [Panther] and VI [Tiger] in my opinion have more maneuverability and certainly more flotation. I have seen in many cases where the Mark V and VI tanks could maneuver nicely over ground where the M4 would bog down. On one occasion I saw at least 10 Royal Tigers [Tiger II] make a counter attack against us over ground that for us was nearly impassable.^[95]

U.S. crews found that on soft ground such as mud or snow, the narrow tracks gave poor (i.e., high) ground pressure compared to wide-tracked second-generation German tanks such as the Panther and the Tiger — these two tanks used the so-called Schachtellaufwerk overlapping, and interleaved roadwheel suspension system pioneered on German half-track vehicles before World War II, but which were troublesome in bad weather conditions and when repairs were needed. Soviet experiences were similar, and tracks were modified to give better grip in the snow. The U.S. Army issued extended end connectors, "grousers" or "duckbills" to add width to the standard tracks as a stopgap solution. Duckbills began to reach front-line tank battalions in July 1944, and were original factory equipment for the heavy M4A3E2 Jumbo to compensate for the extra weight of armor. The M4A3E8 "Easy Eight" Shermans and other late models with wider-tracked HVSS suspension and twinned road wheels on each axle — rather than the single road wheel of the VVSS suspension designs — corrected these problems but formed only a small proportion of the tanks in service even in 1945.

U.S. variants

The M4A1, A2 and A3 compared.

This M32 Tank Recovery Vehicle shows the E8 HVSS track suspension that distributed weight more widely.

M74 Tank Recovery Vehicle.

Vehicles that used the M4 chassis or hull:

• 3in Gun Motor Carriage M10 a.k.a. Wolverine - tank destroyer
• 90 mm Gun Motor Carriage M36 – tank destroyer
• 105 mm Howitzer Motor Carriage M7B1 a.k.a. Priest – self-propelled artillery
• 155 mm Gun Motor Carriage M12 – self-propelled gun, paired in service with the Cargo Carrier M30 (also derived from the Sherman)
• 155/203/250 mm Motor Carriages – 155 mm self-propelled artillery (armed with the Long Tom artillery piece), 8 in. (203 mm) HMC M43, 250 mm (10-inch) MMC T94, and Cargo Carrier T30
• Sexton 88mm (25 Pndr) self-propelled gun and variants
• Flame Tank Sherman – M4A3R3 Zippo, M4 Crocodile, and other flame-throwing Shermans
• Rocket Artillery Sherman – T34 Calliope, T40 Whizbang, and other Sherman rocket launchers
• Amphibious tanks – Duplex Drive (DD) swimming Sherman. A British variant used by U.S. forces.
• Engineer tanks – D-8, M1, and M1A1 dozers, M4 Doozit, Mobile Assault Bridge, and Aunt Jemima and other mine-clearers
• Recovery tanks – M32 and M74 Tank Recovery Vehicles
• Artillery tractors – M34 and M35 prime movers

Foreign variants and use

The Sherman was extensively supplied through Lend-Lease to Britain, the Soviet Union and the Free French. Britain received 17,287 Shermans of various models. The Soviet Union received 4,035 M4A2 Shermans. The Free French was the third largest recipient, taking 657 Shermans 1943-1944. 57 Shermans were delivered to other nations.^[96]

After World War II, Shermans were supplied to some NATO armies; Shermans were used by U.S. and allied forces in the Korean War.

Shermans also went to Israel.^[97] The Israeli up-gunned 75 mm M-50 and 105 mm armed M-51 Super Shermans are remarkable examples of how a long obsolete design can be upgraded for front-line use.^[98] They saw combat in the 1967 Six-Day War, fighting Soviet World War II-era armor like the T34/85, and also in the 1973 Yom Kippur War, proving effective even against newer, heavier Soviet tanks like the T-54 and T-55.

Users

See also

Tanks of comparable role, performance and era

References

Notes

Citations

Further reading

External links

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