M4 Sherman

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The M4 Sherman, formally Medium Tank, M4, was the primary tank used by the United States during World War II. Thousands were also distributed to the Allies, including the British Commonwealth and the Soviet Union, via lend-lease. In the United Kingdom, the M4 was named after Union General William Tecumseh Sherman, following the British practice of naming their American-built tanks after famous American Civil War generals. Subsequently, the British name found its way into common use in the U.S.
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The Sherman evolved from the Grant and Lee medium tanks, which had an unusual side-sponson mounted 75 mm gun. It retained much of the previous mechanical design, but added the first American main 75 mm gun mounted on a fully traversing turret, with a gyrostabilizer enabling the crew to fire with reasonable accuracy while the tank was on the move.[4] 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 made the Sherman superior in some regards to the earlier German light and medium tanks of 1939-41. The Sherman ended up being produced in large numbers and formed the backbone of most Allied offensives, starting in late 1942.

The original Shermans were able to defeat the relatively small German tanks such as the Panzer III and IV they faced when first deployed in North Africa. Later, they found themselves more evenly matched against the newer up-gunned and up-armored [http://en.wikipedia.org/wiki/Panzer_IV Pz.Kpfw. IV ] medium tanks. Shermans were often outmatched by the 45 ton Panther tank and wholly inadequate against the 56 ton Tiger I and later 72 ton Tiger II heavy tanks, suffering high casualties against their heavier armor and more powerful 88 mm L/56 and L/71 cannons. Mobility, mechanical reliability and sheer numbers, supported by growing superiority in supporting fighter-bombers and artillery, helped offset these disadvantages strategically. The relative ease of production allowed huge numbers of the Sherman to be produced. This allowed many divisions, even many infantry divisions, their own organic Sherman assets. Some infantry divisions had more tanks than German panzer divisions did. This was a huge advantage for the Americans.[5]

Production of the Sherman was favored by the commander of the Armored Ground Forces, albeit controversially, over the heavier M26 Pershing, which resulted in the latter being deployed too late to play any significant role in the war. In the Pacific Theater, the Sherman was used chiefly against Japanese infantry and fortifications; in its rare encounters with much lighter Japanese tanks with weaker armor and guns, the Sherman's superiority was overwhelming.

Production of the M4 exceeded 50,000 units, and its chassis also served as the basis for numerous other armored vehicles such as tank destroyers, tank retrievers, and self-propelled artillery. Only the Soviet T-34 tank was produced in larger numbers during World War II.

The Sherman would finally give way to post-war tanks developed from the M26. Various original and updated versions of the Sherman would continue to see combat effectively in many later conflicts, including the Korean War, Arab-Israeli Wars, and Indo-Pakistani War (where it was used by both sides) into the late 20th century.[6] {| class="toc" id="toc"

Contents
[hide] *1 U.S. design prototype
 * 1.1 Doctrine
 * 2 U.S. production history
 * 3 Service history
 * 3.1 Allocation
 * 3.2 First combat
 * 3.3 Pacific Theater
 * 3.4 Post–World War II
 * 4 Armament
 * 4.1 The tank destroyer doctrine
 * 4.2 Gun development
 * 4.3 Miscellaneous
 * 5 Armor
 * 6 Mobility
 * 7 U.S. variants
 * 8 Foreign variants and use
 * 9 See also
 * 10 Notes
 * 11 References
 * 12 External links
 * }

U.S. design prototype
Cutaway Sherman showing transmission and driver seatThe U.S. Army Ordnance Department designed the Medium Tank M4 as a replacement for the M3 Lee and Grant Medium Tanks. The M3 was an up-gunned development of the M2 Medium Tank of 1939, itself 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 panzers, the placement of a 37 mm gun turret on top gave it a very high profile, and the unusual inflexible side-sponson mounted main gun 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 had to be 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 Lee's main gun. This became the Sherman.[7]

The Sherman's reliability benefited from many features first developed in U.S. light tanks during the 1930s, including vertical volute spring suspension, rubber-bushed tracks, and rear-mounted radial engine with drive sprockets in front. The designated 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 deployed 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.[8]

Doctrine
A Sherman tank of 13th/18th Royal Hussars in action against German troops using crashed Horsa gliders as cover near Ranville, Normandy, 10 June 1944As the US approached entry in World War II, armored employment was doctrinally governed by FM 100-5 Operations (published May 1941, the month following selection of the M4 tank's final design). That FM stated that: 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.[9] In other words, the M4 was envisioned to primarily fill the role of a cruiser tank — although the US Army did not use that doctrinal term. The M4 was not primarily 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". Neither was the M4 primarily intended for tank versus tank action. Doctrinally, anti-tank engagements were the primary role of tank destroyers. 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).[10] This early armored doctrine was heavily influenced by the sweeping initial successes of the German blitzkrieg tactics. Unfortunately, by the time M4s reached combat in significant numbers, battlefield demands for infantry support and tank versus tank action far outnumbered the occasional opportunities for cruiser tanks.

Although envisioned primarily as a cruiser-type tank, US doctrine did also contemplate the M4's use in other roles. Unlike some other nations, which had separate medium tank designs tailored specifically for anti-tank roles (e.g., the German PzKw III) and support roles (the PzKw IV), the US intended the M4 to fulfill all roles. Although not optimized for tank versus tank engagements or infantry support, the M4 was capable of performing these missions to varying degrees. In the Pacific Theater, the Sherman was used chiefly against Japanese infantry and fortifications; in their rare encounters with lighter Japanese tanks with weaker armor and guns, the Shermans were vastly superior.

The official doctrine of the time had Shermans as a sort of infantry tank. All anti-tank work was supposed to be done by tank-destroyer crews. Speed was essential in order to bring the tank-destroyers from the rear to destroy incoming tanks. Thankfully, for Sherman crews, this doctrine was not entirely used as it would create a small time window of vulnerability in the armored battalion until tank destroyers moved to the front. Obviously this would make it harder for an armored force to achieve a breakthrough, a main objective of armor, if the enemy had tanks. It would also be easier for an opposing armored force to achieve a breakthrough against an American tank battalion which would not have all of its anti-tank assets at the front during the beginning of any attack.[11]

U.S. production history
See also: American armored fighting vehicle production during World War IIM4A1 with cast hullM4 and M4A1 (shown), the first Shermans, share the inverted U backplate and inherited their engine and exhaust system from the earlier M3 Lee.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 US, it was displayed in London and is now an exhibit at Bovington Tank Museum.[12] [13]

In World War II, the U.S. Army ultimately fielded 16 armored divisions, along with 70 independent tank battalions; the U.S. Marine Corps also fielded six independent Sherman tank battalions for a total of 76, enough for 25 more armored divisions. A third of all Army tank battalions, and all six Marine tank battalions, were deployed to the Pacific Theater of Operations (PTO).[14] 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 warships and other naval vessels.[15] The use of steel for naval construction amounted to the equivalent of approximately 67,000 tanks; and consequently only about 53,500 tanks were produced during 1942 and 1943.[16]

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 was not meant to indicate it was better than the 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 M4 by its fully cast upper hull; the M4A4 had a longer engine system that required a longer hull, a longer suspension system, and more track blocks; M4A5 was an administrative placeholder for Canadian production; and the M4A6 had an elongated chassis, but fewer than 100 of these were 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,[17] the M4A6 a [http://en.wikipedia.org/wiki/Caterpillar_Inc. Caterpillar ] RD1820 radial.[18] These, plus the M4A4, which used the Chrysler A57 multibank engine, were mostly supplied to Allied countries under Lend-Lease.[19] "M4" can refer specifically to the initial sub-type with its Continental radial engine, or generically, to the entire family of seven Sherman sub-types, depending on context. Many details of production, shape, strength and performance improved throughout production, without a change to the tank's basic model number: 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.<sup class="reference" id="cite_ref-Berndt.2C_p.195_2-3">[3]

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 HE 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 new distinctive mantlet in the original turret. The first standard-production 76 mm gun Sherman was an M4A1, accepted in January 1944, and 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 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 HVSS (horizontal volute spring suspension) suspension with wider tracks to distribute weight, and the smooth ride of the HVSS with 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; few saw combat, and most remained experimental. Those that saw action included the bulldozer blade for the Sherman dozer tanks, Duplex Drive for "swimming" Sherman tanks, R3 flamethrower for Zippo flame tanks, and the T34 60-tube Calliope 4.5" rocket launcher for the Sherman 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 M32 and M74 "tow truck"-style recovery tanks with winches, booms, and an 81 mm mortar for smoke screens; M34 (from M32B1) and M35 (from M10A1) artillery prime movers; M7B1, M12, M40, and M43 self-propelled artillery; and the M10 Wolverine (Achilles, in British service) and M36 Jackson tank destroyers.
 * M4A4 Cutaway

Service history
First type in U.S. service: A U.S. 7th Army M4A1 lands at Red Beach 2, Sicily 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 compared to others that protruded above sloping armor.===Allocation=== See also: Lend-Lease Sherman tanksDuring World War II, approximately 19,247 Shermans were issued to the US Army and about 1,114 to the US Marine Corps.<sup class="reference" id="cite_ref-19">[20] The U.S. also supplied 17,184 to Great Britain (some of which went to the Canadians and the Free Poles), while the Soviet Union received 4,102<sup class="reference" id="cite_ref-20">[21] and an estimated 812 were transferred to China.<sup class="reference" id="cite_ref-21">[22] 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 US armored Divisions when there was a turn of events in the Western Desert. Rommel had taken Tobruk, and Egypt (and 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.<sup class="reference" id="cite_ref-Fletcher_p93_11-1">[12]

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 with long barreled 50 mm L/60 guns, and Panzer IVs with short barreled 75 mm L/24 guns<sup class="Template-Fact" style="white-space: nowrap;">[citation needed]. Additional M4s and M4A1s replaced M3 Lees 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. Some M4s and M4A1s continued in U.S. service for the rest of the war.

Encounters with a company of Tiger Is, with their heavier armor and 88 mm L/56 guns, in Tunisia were typical of the mid-war period: the fearsome quality of a few German heavy tanks and their crews could sometimes be overcome by the quantity and mobility of the Shermans, supported by artillery and airpower, but sometimes at a great cost in U.S. tanks and crewmen. By June 1944, the Panzer IV had been up-gunned with a 75 mm L/48 weapon, and 75 mm Shermans were outgunned on a regular basis. 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.<sup class="reference" id="cite_ref-22">[23] Indeed, even the Imperial Japanese Army (IJA) deployed only their 2nd Tank Division to the Pacific during the war.<sup class="reference" id="cite_ref-23">[24] The environment in which armor from both sides had to operate was generally described as tropical rain forests, which most armies simply classified as jungles. For this type of terrain, the Japanese and the Allies found light tanks easier to transport, maneuver and employ.<sup class="reference" id="cite_ref-24">[25]

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.<sup class="reference" id="cite_ref-25">[26] 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.<sup class="reference" id="cite_ref-26">[27] 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<sup class="Template-Fact" style="white-space: nowrap;">[citation needed], the Japanese developed the Type 3 Chi-Nu and the heavier Type 4 Chi-To; both tanks were armed with 75 mm guns, but 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.<sup class="Template-Fact" style="white-space: nowrap;">[citation needed]

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, simply went through the thin armor of Japanese tanks, and often 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 cannon fire seldom destroyed Japanese fortifications.<sup class="reference" id="cite_ref-27">[28] <sup class="reference" id="cite_ref-28">[29]

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 howitzer. The Sherman remained a common U.S. tank in the Korean War. Despite no longer being the primary US tank it fought alongside the M26 Pershing and M46 Patton. Both the Sherman and T-34 were comparable and could destroy each other when hit. The Sherman had better optics, which gave it a better chance of scoring a first round hit.<sup class="reference" id="cite_ref-Osprey_Publications_M26_Pershing_29-0">[30]

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

Armament
The gun on the original M4 was the short-barreled medium-velocity 75mm 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 British 6 pdr (57 mm) guns being able to take out 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 seeming to prove the 76 mm able to take out the Tiger and the Panther without worry, AGF was not worried about the Tiger that much. These tests 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 numbers of Tigers.<sup class="reference" id="cite_ref-30">[31]

Despite the Bureau of Ordnance development of new 76mm and 90 mm anti-tank guns, Army Ground Forces rejected their deployment on U.S. tanks as unnecessary. Even in 1943, most German AFVs (later models of the Panzer IV, StuG III, and Marder III) mounted 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 75mm-armed M4 was the impetus to begin production of 76mm-armed M4s in April 1944.<sup class="reference" id="cite_ref-31">[32] The U.S. 76 mm proved comparable in penetrating power to the 7.5 cm KwK 40,<sup class="reference" id="cite_ref-32">[33] the most common German tank gun encountered during the fighting in France, however transfer of the tanks to the front started slowly, and most tanks still had M3's, even by Operation Cobra.<sup class="reference" id="cite_ref-33">[34]

The 76 mm gun could penetrate roughly 88 mm of armor at 1000 m, just around the average tank engagement range noted by the Canadians. This was enough to reliably penetrate a PzIV's glacis. However, the 76 mm was not powerful enough against the frontal armor of a Panther. Due to its angle, the Panther's glacis gave it an effective thickness of 140 mm (5.51 in). Shermans had to get relatively close, due to both the armor and low-flash powder of the Panther which made it harder to spot. Sherman crews also had issues with firing from range as the Sherman's high flash powder made their shots easy to spot. Their gun sights were fixed magnification compared to the German's multiple magnification settings with added anti-glare filter. In Summer 1944, after breaking out of the bocage and moving into open country, U.S. tank units who were engaged at range from German defensive positions sometimes took 50% casualties before spotting where the fire was coming from.<sup class="reference" id="cite_ref-34">[35]

The Sherman was first equipped with the L/40 75mm M3 Gun, which firing the usual M61 round could penetrate 77 mm at 100m and 61 mm at 1000m. The average combat range noted by the Americans for tank vs. tank action was 800m to 900m. Conditions later in the war necessitated up-gunning to the 76mm L/55 M1A2, which could penetrate 124 mm at 100m and 83 mm at 1000m using the usual M79 round. The M1A2 helped to equalize the Sherman and the PzIV in terms of firepower, although the M4 was still under-gunned compared to the Panther's much more powerful L/70 75mm gun, which could penetrate 138 mm at 100 m<sup class="Template-Fact" style="white-space: nowrap;">[citation needed] and 111 mm at 1000m using the usual PzGr.39/42 round. The British-developed Sherman Firefly was an M4 re-gunned with their QF 17 pounder anti-tank gun. The 17 pdr was a 76 mm gun and had a 55 caliber barrel, but introduced a much bigger charge which allowed it to penetrate 140 mm (of RHA sloped at 30 degrees) at 100 m and 120 mm at 1000 m using APC Mk.IV shot.<sup class="reference" id="cite_ref-35">[36] This gun allowed the Firefly a slight firepower advantage over the Panther, although the muzzle flash due to unburnt powder from the increased charge left crews momentarily blinded after firing.<sup class="reference" id="cite_ref-ReferenceA_4-1">[5]

The tank destroyer doctrine
Gen. Lesley J. McNair was head of Army Ground Forces. McNair, an artilleryman, championed the tank destroyer 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 self-propelled tank destroyers and towed antitank guns. Self-propelled tank destroyers, called "gun motor carriages" as were any US Army self-propelled armored vehicles mounting an artillery piece of heavy calibre, and 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.<sup class="reference" id="cite_ref-36">[37]

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.<sup class="reference" id="cite_ref-37">[38]

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 hit the ground on undulating terrain. Ordnance reduced the barrel length by 15 inches (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.<sup class="reference" id="cite_ref-38">[39]

Although tests against armor plate suggested the new M1A1 76 mm gun would be adequate, testing against captured Panther tanks was never done. This would have shown the gun could not penetrate the glacis plate of the Panther at any distance, and could only penetrate the center of the gun mantlet at 100 meters.<sup class="reference" id="cite_ref-39">[40] 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 discovered, it was insisted that the superior mobility of the open-topped tank destroyers would obviate this deficiency; this assumption proved 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 TDs 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.<sup class="reference" id="cite_ref-40">[41]

In testing prior to the invasion of Normandy, the new 76 mm gun on the M4 Sherman was found to have a undesirable 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.<sup class="reference" id="cite_ref-41">[42] British Firefly in Namur, 1944The 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 57mm 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 easily penetrate the Panther's gun mantlet at combat range;<sup class="reference" id="cite_ref-42">[43] moreover it could penetrate the front and side armor of the Tiger I at nearly the same range that the Tiger I could penetrate the Sherman.<sup class="reference" id="cite_ref-43">[44] Late in 1944, the British began to produce saboted rounds for the 17 pounder gun, which could readily penetrate the armor of even the Tiger IIs, but these rounds were not as accurate 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.<sup class="reference" id="cite_ref-44">[45]

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. However, this new projectile was still unable to penetrate the glacis plate of the Panther tank although it could penetrate the turret mantlet of the Panther at longer ranges than standard ammunition; it brought the U.S. 76 mm gun closer in performance to the British 17 pounder using standard APC ammunition. 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.<sup class="reference" id="cite_ref-45">[46]

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.<sup class="reference" id="cite_ref-46">[47]

Additionally, 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 gun. Approximately 100 tanks 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 that the logistics 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.<sup class="reference" id="cite_ref-47">[48]

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. However, with a regular AP (Armor Piercing shot) ammunition (M79) or APCBC (M62) shells, the 76 mm might knock out a Panther only at close range with a shot to its mantlet or flank. At long range, the Sherman was badly 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 the losses of Sherman tanks suffered by the U.S. Army in Europe.<sup class="reference" id="cite_ref-48">[49]

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.<sup class="reference" id="cite_ref-49">[50] 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 an hour. This gave a hit probability of 70% on enemy tanks at ranges of 300 to 1200 yards.<sup class="reference" id="cite_ref-50">[51] 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.<sup class="reference" id="cite_ref-51">[52] 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"). Other units devised other similar devices.<sup class="reference" id="cite_ref-52">[53]

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 105mm-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.

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 splattered against the German tank, in addition to blinding the enemy gunner's excellent optics, the acrid smoke would get sucked inside the tank, and together with the fear of the fire spreading inside the tank, cause the crew to abandon the tank.<sup class="reference" id="cite_ref-53">[54] There were several recorded instances where white phosphorus shells "knocked out" German tanks in this fashion.<sup class="reference" id="cite_ref-54">[55]

Armor
This early 75 mm gun turret on an M4A4 shows the single hatch — note the additional rectangular external (welded on) applique 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).<sup class="reference" id="cite_ref-Zaloga14_55-0">[56] The M4’s gun mantlet was also protected by 76 mm (2.99 in) of armor<sup class="reference" id="cite_ref-Zaloga14_55-1">[56] sloped<sup class="noprint Inline-Template" style="white-space: nowrap;">[clarification needed] at 30 degrees,<sup class="reference" id="cite_ref-Reid215_56-0">[57] The turret side armor was 50 mm (1.97 in) a 5-degree angle<sup class="reference" id="cite_ref-Reid215_56-1">[57] while the rear was 64 mm at a 90-degree angle and the turret roof was 25 mm thick.<sup class="reference" id="cite_ref-Hart27_57-0">[58] The hull front sported 51 mm armor.<sup class="reference" id="cite_ref-Zaloga14_55-2">[56] <sup class="reference" id="cite_ref-Hart27_57-1">[58] Although the Russian T-34 is often credited for introducing sloped armor in a production tank<sup class="Template-Fact" style="white-space: nowrap;">[citation needed], the Sherman's upper hull was angled at 56 degrees, while the lower half of the hull was curved.<sup class="reference" id="cite_ref-Hart27_57-2">[58] The earlier U.S. M2 and M3 medium tanks also had sloped armor. The hull sides were 38–45 mm (1.50–1.77 in) thick,<sup class="reference" id="cite_ref-Reid215_56-2">[57] <sup class="reference" id="cite_ref-Buckley110_58-0">[59] and vertical.<sup class="reference" id="cite_ref-Hart27_57-3">[58] The hull rear—which protected and was offset from the rear radiator on some versions—was 38 mm (1.50 in) to the vertical or sloped to 85 degrees.<sup class="noprint Inline-Template" style="white-space: nowrap;">[clarification needed] The hull roof was 25 mm (0.98 in).<sup class="reference" id="cite_ref-Hart27_57-4">[58]

The armor of the M4 was effective against most early war anti-tank weapons,<sup class="reference" id="cite_ref-Zaloga14_55-3">[56] but was easily penetrated by later German tank guns 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 75 mm L/48 tank guns would penetrate up to a range of 1,370<sup class="reference" id="cite_ref-59">[60] – 1,500 meters, and larger guns could penetrate past 2,000 metres.<sup class="reference" id="cite_ref-60">[61] Regardless of this vulnerability, historian John Buckley has stated the M4 was "moderately superior" to the relatively small, but older Panzer IV. Although the later modeled 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."<sup class="reference" id="cite_ref-61">[62]

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, even though it had little effect. Mounting sandbags around a tank had little effect against high-velocity anti-tank gunfire, but 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.<sup class="reference" id="cite_ref-62">[63] M4A3E2 Sherman Jumbo. Some units replaced the original 75 mm gun with a 76 mm gun.The M4A3E2 Sherman Jumbo variant had even thicker frontal armor than the Tiger I, with a totally flat sloped glacis plate, having no protrusions from the forward crew hatchways which the original M4 designs possessed and a thicker welded mantlet for the main gun. Intended for the assault to break out of the Normandy beachhead, it entered combat in August 1944.<sup class="Template-Fact" style="white-space: nowrap;">[citation needed]

The M4 had an escape hatch on the hull bottom to help the crew survive and, 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. Note also the Culin hedgerow cutter on the front, a field improvisation to break through the thick hedgerows of the Normandy bocage.Research conducted by the British No. 2 Operational Research Section, after the Normandy campaign, concluded 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.<sup class="reference" id="cite_ref-63">[64] John Buckley, using a case study of the 8th and 29th Armoured Brigades found that of the 166 Shermans knocked out in combat during the Normandy campaign, only 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.<sup class="reference" id="cite_ref-Buckley127_64-0">[65] 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<sup class="reference" id="cite_ref-Zaloga_2008.2C_p._116-118_65-0">[66]

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. 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 by a factor of four.<sup class="Template-Fact" style="white-space: nowrap;">[citation needed] 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", the cigarette lighter which had the slogan "Lights up the first time, every time!" Polish tankers referred to it as "The Burning Grave".<sup class="Template-Fact" style="white-space: nowrap;">[citation needed]

Many think that the fires for which the Sherman is infamous were a result of its gasoline engine<sup class="Template-Fact" style="white-space: nowrap;">[citation needed]. Actually, most of the tanks of the time used gasoline engines. Fuel fires occasionally occurred, but such fires were far less common and less deadly than ammunition fires.<sup class="reference" id="cite_ref-Zaloga_2008.2C_p._116-118_65-1">[66] In many cases the fuel tank of the Sherman was found intact after a fire. Tankers describe "fierce, blinding jets of flame," which is inconsistent with gasoline-related fires but fits cordite flash.<sup class="reference" id="cite_ref-Buckley127_64-1">[65]

The armor of the Sherman comparatively to the Panthercan be described by statements used in a report to General Eisenhower at SHAEF: 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 on the turret only chipped the paint.<sup class="reference" id="cite_ref-66">[67] ==Mobility== Vertical volute springs of Stuart tank with similar suspension system.The U.S. Army restricted the Sherman's height, width, and weight so that it could be transported via typical bridges, roads, and railroads. This aided strategic, logistical, and tactical flexibility.

The Sherman had good speed both on- and off-road. Off-road performance varied. In the desert, the Sherman's rubber 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 Armoured Division reports, definitely superior to that of our tanks<sup class="reference" id="cite_ref-67">[68] However, whilst this may have held true compared with the 1st generation German tanks such as the PzKfpw. III & IV, actual comparative testing with the second generation German tanks (Panther & Tiger) conducted by the Germans at their Kummersdorf testing facility as well as by the US 2nd Armored Division, proved otherwise.

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"<sup class="reference" id="cite_ref-Michael_Green_Page_53_68-0">[69] 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 exceeds that of the Sherman"<sup class="reference" id="cite_ref-Michael_Green_Page_53_68-1">[69] Staff Sergeant and Tank Platoon Sergeant Charles A Carden completes the comparison in his report: "The Mark V [Panther] and IV [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 B] make a counter attack against us over ground that for us was nearly impassible"<sup class="reference" id="cite_ref-Michael_Green_Page_53_68-2">[69] U.S. crews found that on soft ground such as mud or snow, the narrow tracks gave poor ground pressure compared to wide-tracked second-generation German tanks such as the Panther and the Tiger. 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 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 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.Main article: M4 Sherman variantsVehicles that used the M4 chassis or hull:
 * 3in Gun Motor Carriage M10 - Wolverine Tank Destroyer
 * 90 mm Gun Motor Carriage M36 - Jackson Tank Destroyer
 * 105 mm Howitzer Motor Carriage M7B1 - self-propelled artillery, aka Priest
 * 155 mm Gun Motor Carriage M12 - GMC M12 with Cargo Carrier M30 (both used Sherman components)
 * 155/203/250 mm Motor Carriages - 155 mm GMC M40 (armed with the Long Tom artillery piece), 8 in. (203 mm) HMC M43, 250 mm (10-inch) MMC T94, and Cargo Carrier T30
 * 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
See also: Lend-Lease Sherman tanks, Postwar Sherman tanks, Sherman Firefly, and Grizzly I cruiserThe Sherman was extensively supplied through Lend-Lease to Allied countries<sup class="Template-Fact" style="white-space: nowrap;">[citation needed]. Britain took nearly 80% of Lend-Lease deliveries<sup class="Template-Fact" style="white-space: nowrap;">[citation needed], some of which was passed on to other allies. Soviet Union between 1942 and 1945 years has received 3664 tanks M4A2 with diesel engines. Some of these remained in service for many years<sup class="Template-Fact" style="white-space: nowrap;">[citation needed]. 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<sup class="reference" id="cite_ref-69">[70]. 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 in front-line use.<sup class="reference" id="cite_ref-70">[71] 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.
 * Foreign users