Introduction and Development
Introduction and Development
The M10 3in Gun Motor Carriage was the most widely used American tank destroyer of the Second World War, seeing service in Tunisia in 1943, Italy in 1943-45, north-western Europe from D-Day to the end of the war and in the Pacific. It was produced by mounting a 3in gun on the chassis of an M4A2 Sherman medium tank, but with reduced armour to save weight and cost.
Work on mounting an anti-tank gun on a suitable chassis began in 1940, using the 37mm gun and a variety of different base vehicles. This produced the M6 37mm gun carriage, based on a 3/4 ton truck, of which 5,380 were built in April-October 1942, but by then the 37mm gun was obsolete and work had already moved onto designs with heavier guns. This produced the M3 75mm Gun Motor Carriage, which had a 75mm gun on the chassis of a M3 half-track personnel carrier. 2,202 were produced between February 1942 and April 1943.
These were both seen as interim designs, to be used until a more powerful fully tracked tank destroyer could be built. Early projects were based on the M3 medium tank. Work on the T24 3in Gun Motor Carriage began in September 1941, but the resulting vehicle was considered to be too high and the gun mount caused problems. The T24 project was cancelled in March 1942. Work then moved onto the T40, with an obsolete M1918 3in gun in a lower mounting. This was standardised as the M9 3in GMC in April 1942, but a shortage of guns meant that the project was cancelled in August 1942.
In April 1942 work began on the T35 3in Gun Motor Carriage. This used the chassis of the M4A2 Sherman medium tank (using twin General Motor engines) and carried its 3in (76mm) gun in an open topped turret.
Two pilot models were produced. The T35 had the standard Sherman superstructure with a low turret loosely based on the turret designed for the T1 Heavy Tank.
Early combat reports from the Philippines suggested that sloped armour was more effective that the flat sided armour of the Sherman. A second prototype, the T35E1, was developed with a lower silhouette and sloped side armour on the superstructure. The two prototypes underwent tests and the sloped armour won out. The T35E1 was accepted for production in May 1942 and standardised as the M10 3in Gun Motor Carriage in June 1942.
Series production began in September 1942 at the Grand Blanc Tank Arsenal. The main justification for the more lightly armoured tank destroyer was that made it possible to build a vehicle with more firepower than the equivalent tank, but at lower cost. The M10 cost $47,905 to produce, a saving of nearly $13,000 on the $60,215 needed for a M4A2 medium tank, so it did achieve this aim.
The M10 was produced by the Grand Blanc Tank Arsenal. A total of 4,993 were built between September 1942 and December 1943.
Early production M10s had a small counterweight at the back of the turret. This was later replaced with a much larger counterweight which protruded some way back from the five sided welded turret. Late production vehicles had a modified counterweight with a flat extension, known as the 'duck-bill' counter-weight. This version of the turret also had more storage in the rear of the turret.
The prototypes had a rounded turret with sloped sides, but production vehicles used a five sided turret which was wider at the back than the front.
When travelling the turret was rotated backwards, and the gun was rested in a travel cradle on the back of the superstructure.
The thin armour of the M10 caused concern throughout its service career. By the end of 1944 it was increasingly common to see extra protection such as sandbags mounted on the hull in an attempt to protect against the new German infantry antitank weapons such as the Panzerfaust. The open topped turret was also a concern, and a number of impromptu armoured covers were produced in an attempt to solve this problem. The same thing was done in the British army, where blast shields were sometimes installed.
In order to boost production a new version, the M10A1 3in Gun Motor Carriage, was developed. This was based on the chassis of the M4A3 Sherman, and was powered by a Ford G8 engine. Production of the M10A1 began in October 1942 at Ford and a total of 1,038 were built before production ended in September 1943.
The M10A1 was also produced at Grand Blanc, where 675 were built between September and November 1943. Three hundred of these vehicles were actually completed as M36 Gun Motor Carriages.
The M10 entered combat during the Tunisian campaign of 1943, initially serving with the 899th Tank Destroyer Battalion. This battalion was involved in the fighting at El Guettar on 23 March 1943 when an attack by the 10th Panzer Division was repulsed. The 899th lost seven of its M10s. The new vehicle was a great improvement on the earlier M6 and M3 tank destroyers, and gave the tank destroyer battalions a fully tracked reasonably armoured vehicle. On the older vehicles the crew were effectively crouched behind a small shield on the back of a truck, with a limited range of traverse for the gun, but here they had a fully (if thinly) armoured chassis and superstructure and a fully traversable turret.
The M10 was used during the invasion of Sicily, having replaced the earlier M3 and M6 tank destroyers as quickly as deliveries allowed. The M10 was the standard US Tank Destroyer by the time of the invasion of mainland Italy in September 1943. By this point the tank-destroyer doctrine was badly outdated. It was based on the idea that the Germans used their tanks in large masses to create massive breakthroughs in the enemy lines and was based on a study of their invasion of the west in 1940. By 1943 the Germans were using their tanks in small units and in close cooperation with infantry and artillery, in a very effective combined arms tactic. In Italy the Germans were almost always on the defensive, so a new role was needed for the M10.
At the start of the Italian campaign the tank destroyer battalions were normally attached to infantry and armoured visions, and were used whenever the divisional commanders needed extra firepower. Its 3in gun gave it more firepower than the M4 Sherman, and so it was more effective against German strong points and fortifications. The M10 was often used as mobile artillery, although the limited maximum elevation of the gun limited range, and the front of the vehicle often had to be driven onto a bank or up a slope to increase range.
The M10, with its thin armour and open topped turret, was ill suited to the infantry support role it often now performed. It was often used to provide direct fire support, attacking German fortifications. Because the Germans rarely operated tanks without infantry support the open topped turret left the M10 crews vulnerable to snipers and even grenades, while the thin armour could easily be penetrated by the German 75mm PaK 40 anti-tank gun. Their nearest German equivalent, the StuG III Ausf G, had 80mm of frontal armour and was fully enclosed. In contrast the M10 had at most 37mm of armour.
The M10 took part in the initial landings on the mainland of Italy, the slow advance up the peninsula including the fighting at Cassino, the advance on Rome, the advance to the Gothic Line, and the final advance into the Po Valley in 1945.
The M10 was used at Anzio, where the 601st, 645th and 701st Tank Destroyer Battalions operated the type. Here it was often used for indirect fire, so acted as mobile artillery rather than in its intended role. The first two battalions were independent battalions attached to the 3rd and 45th Divisions, while the 701st was the organic tank destroyer battalion of the 1st Armoured Division.
Once again many US divisional commanders asked for their vulnerable tank destroyers to be replaced with fully armoured tanks, but once again General McNair opposed them. His argument now was the major tank battles he was expected would happen after the D-Day landings. The idea that the German might fight a prolonged defensive battle doesn't seem to have figured in his plans.
D-Day and north-western Europe
The M10 was still the main American tank destroyer during the D-Day landings. Once again it was normally used as an infantry support weapon, and once again its open topped turret and thin armour made it vulnerable to German weapons, especially in the bocage country of Normandy.
The M10 did perform a useful role in Normandy. The standard Sherman still had the less powerful 75mm gun, and only a small number of tanks with the 76mm gun were available, so the M10 had the most powerful tank gun available to the US forces at the start of the campaign. They were also an effective infantry support weapon in the hedgerows, despite their vulnerability, able to provide accurate and rapid support to help the infantry get past German strong points.
The practise of allocating tank destroyer battalions to infantry divisions became even more established in France than it had been in Italy, and the battalions were often sub-divided, with individual companies attached to infantry battalions.
During the fighting in Normandy the Americans came face to face with the Panzer V Panther in larger numbers than in Italy, and quickly discovered that the standard M10 with its 3in gun struggled to knock out the Panther. The more powerful 76mm gun (which fired the same 3in ammo) had more chance of penetrating the Panther's armour, and it became more common as more 76mm armed Shermans and M18 76mm Gun Motor Carriage 'Hellcats' became available. Even so at the start of the campaign the M10 was the American armoured vehicle with the most chance of taking on the heavier German tanks.
The 654th, 702nd, 703rd and 803rd Tank Destroyer Battalion operated the M10 from D-Day onwards. The 644th, 813th, 818th and 899th, entered combat with it in July 1944, the 634th, 814th and 893rd in August 1944, the 771st and 773rd from September 1944, the 776th from October 1944, and the 821st and 823rd from December 1944. Some of these battalions later converted to the M36.
The M10 was used by the French 2nd Armoured Division, and took part in the liberation of Paris in August 1944.
In October 1944 the M10 was used during in the occupation of Aachen, the first German city to be captured by the Allies.
The M10 took part in the difficult fighting in the Huertgen forest just inside Germany in the autumn of 1944. This was mainly an infantry battle, but tank destroyers and tanks often had to be called on to deal with limited German tank attacks.
The M10 was used extensively during the Battle of the Bulge. Early in the battle the M10s were used as part of the rearguard attempting to hold up the German advance. Amongst the units involved was the 644th Tank Destroyer Battalion, which took part in the defence of Elsenborn ridge.
The Battle of the Bulge demonstrated that the towed anti-tank battalions were no long effective. As a result most of them were converted to the M10, using vehicles freed up as existing M10 units converted to the M18 or the M36.
The M10 was used in Operation Dragoon, the invasion of the south of France. Some took part in the initial invasion on 15 August 1944, with some using wading gear to get ashore. The 645th Tank Destroyer Battalion used the M10 during the invasion, but converted to the M36 early in 1945. The 601st Tank Destroyer Battalion also used the M10 during Operation Dragoon.
The M10 made its combat debut in the Pacific during the invasion of Kwajalein in February 1944, where it was used as substitute equipment for the 767th Tank Battalion, supporting the 7th Division. The M10 was used to attack Japanese palm-tree bunkers that were too tough for the 75mm gun of the M4 Sherman.
The first tank destroyer battalion to fight in the Pacific was the 819th Tank Destroyer Battalion, which used its M10s on the Palau Islands in June 1944.
The 710th Tank Battalion, which fought with the 81st Infantry Division during the invasions of Angaur in August 1944 and Peleliu in September-November had four companies, three equipped with the M4A1 Sherman and one with the M10.
The M10 was also used on New Guinea, including at Aitape, and on Saipan and Tinian in the summer of 1944.
Saipan was a rare example of a battle involving significant numbers of Japanese tanks, and the M10 was actually used in the tank destroyer role, unusual in the Pacific theatre.
Three tank destroyer battalions (the 632nd, 637th and 640th) were used on Luzon and the 632nd also fought on Leyte early in 1945.
The tank destroyers were not at all suited to combat in the Pacific. One standard Japanese anti-tank technique was to use infantry to swarm over enemy armour, and the open turrets of the tank destroyers left them very exposed to this form of attack. As a result the tank destroyers were normally used as mobile artillery, fighting from a long distance and with infantry protection.
The M10 served with the British as the 3in SP, Wolverine. By 1944 the British were also more aware of the need for more powerful anti-tank guns than the Americans, and produced an upgunned version, the 17pdr SP, Achilles. The same powerful anti-tank gun was used in the Sherman Firefly, the most effective Allied tank to be available in large numbers during the battles in north-western Europe in 1944-45.
The Wolverine was used in Italy by British and South African units. The 2nd Anti-Tank Regiment used them to support the Polish 2nd Armoured Division.
The Achilles was used in Italy from 1944 in a response to the increasing number of Panzer V Panthers, Panzer VI Tiger Is and Panther turrets used in defensive positions.
The Achilles was used in north-western Europe after the D-Day landings. They were also used by the Royal Canadian Artillery, which operated the type to the end of the war.
Although the M10 was soon withdrawn from American service, it did see some combat with other nations. The Egyptian Army had a small number of ex-British vehicles, and used them in 1948. This included a number of the 17pdr Achilles. Israel captured some of the Egyptian vehicles and bought a number of their own.
The M10 was the standard version of the vehicle, using the chassis of the M4A2 Sherman.
The M10A1 was the designation given to Ford-produced M10s. These used the chassis of the M4A3 Sherman and had a Ford petrol engine. The two types are very difficult to tell apart.
M35 Prime Mover
The M35 Prime Mover was the designation given to 209 M10A1 tank destroyers that had their turrets removed in January 1944 and were used as prime movers for the heavy artillery and armoured personnel carriers for the gun crews.
The T72 was a design for a version of the M10 that would have been armed with the 76mm gun used on the M18 Hellcat and later Shermans.
3in SP, Wolverine
The British designation for the standard M10 was 3in SP, Wolverine. These were used to replace towed 17pdr anti-tank guns in some batteries of anti-tank regiments, and were used in this role during the campaign in north-western Europe in 1944-45.
17pdr SP, Achilles IC
The 17pdr SP, Achilles IC was the designation given to the M10 with a 17pdr anti-tank gun and the intermediate type of turret. Most Wolverines were converted into Achilles, starting late in 1944.
17pdr SP, Achilles IIC
The 17pdr SP, Achilles IIC was the designation given to the M10 with a 17pdr anti-tank gun and the late turret type with the duck-bill counterweight. This was the most numerous British version.
Hull Length: 19ft 7in
Hull Width: 10ft
Height: 8ft 1.5in
Crew: 5 (commander, driver and three gun crew)
Engine: M10: Twin GMS6-71 diesel engines: M10A1: Ford GAA V8 petrol engine
Max Speed: 30mph road, about 20mph cross-country
Max Range: 200 mile road radius
Armament: M7 3in anti-tank gun, .50in Browning anti-aircraft gun