This is the T-35 prototype of April 1942 that was based on the M-4A2 hull with the rear and side armor reduced to only 25 mm, but with the hull’s front armor reinforced to protect the transmission and the final drives. The turret had 50 mm of armor on the front and 25 mm on the sides and the rear. The T-35 was powered by two GM diesel engines and colud reach 50 km/h. This vehicle weighed 26.8 tonnes, and measured 5.70 meters long (hull), 2.56 meters wide and 2.66 meters tall and finally was not selected to go into production.This is the T-35E1 prototype, which would be chosen to be manufactured and was commonly known as “M-10 GMC tank destroyer”. It had some improvements compared to the T-35 as the hull’s sloped armor and was lower. The turret was the same installed on T-35 although it had a partial roof covering the gun breech. This pilot model measured 5.67 meters long (hull), 3.04 meters wide and 2.47 meters tall and carried fifty-four 76 mm rounds. All turret was of cast armor but the production model would carry rolled homogenous armor (RHA), which offered greater protection.The standard M-10 GMC had some differences with the T-35E1 pilot model at first glance. The turret had no reverse sloped armour that could divert enemy rounds to the hull and the vehicle’s front no longer had the applique piece and was built in all cast armour. Thirty-two bosses were welded to the turret and the hull for the installation of track grouser racks or extra armor if necessay. because protection was still one of its weak points because mobility and firepower over protection have prevailed in its design. Later, in July 1943 only the glacis bosses were retained.The M-10 GMC had the same hull as the M-4A2 Sherman tank but lightened. Its armor was noticeably thinner, keeping the thickness on the front but reducing the sides to only 25 mm. The doctrine of use of the tank destroyer units foresees the confrontation with the enemy tanks from covered positions or ambushes if possible, always avoiding the frontal and direct confrontation. This doctrine forced them to flee in case the combat was unfavorable, for what they counted on their good mobility and lightness to escape.The turret was pentagonal and without a roof in most of it, which can be considered a failure. This made them enormously vulnerable when they crossed urban areas or forested areas prone to ambush, and the units in the battlefield tried to alleviate it with different assemblies, installing a kind of armored hut in some cases. The turret’s turning system was manually operated and it took 80 seconds to take a full turn!. This was a terrible setback in cases of melee combat and although the installation of an Oilgear hydraulic traversing engine was studied, it was finally discarded.The enormous weight of the barrel caused instability problems and the vehicle was prone to overturn if the turret rotated while on inclined terrain. Some solutions were sought such as the installation of track grousers in the rear of the turret, but it was not effective. Finally at the end of January 1943 it was decided to install a set composed by two triangular-shaped counterweights, weighing 1,700 kg total, but this set was too hevy and in June it was installed another lighter of 1,150 kg.M-10 GMC was manned by 5 members. The driver and the assitant/radio operator were in the front of the hull and the commander, loader and gunner were inside the turret. The driver and his assistant had periscopes, but the driver had one on the edge of the hull because he had no vision to his left side due at design of the hull hatches.M-10 tank destroyer had two Detroit Diesel 6-71 engines mounted in tandem that produced 375 hp. This set was designated as “General Motors 6046” and had the distinction of being disconnected from the common crankshaft to operate independently, in addition, if any of them was damaged or damaged, the other engine could continue moving the vehicle.The main weapon was the 76mm M-7 gun, which was installed in an M-5 gun mount, which allowed to exchange this gun with a 105mm howitzer or the British 17-pdr gun. This gun used 5 different types of ammunition: M62/M62A1 (APCBC/HE-T), M79 (AP-T), T4/M93 (HVAP-T), M42A1 (HE) and M88 HC B1 smoke round. The main antitank rounds were the T4/M93, able to penetrate 135mm of armor, the M62/M62A1 round, able to penetrate 88mm and the M79 round, able to penetrate 92mm, all at distances of 900 meters.Chrysler’s Fisher Tank Division was responsible for the exclusive manufacture of the M-10, and from September 1942 to December 1943 manufactured 4,993 vehicles, applying some slight modifications and improvements during production. This tank destroyer was in service with 15 countries, including UK (Achilles), Soviet Union, South Africa, France, Canada, Poland or Italy.(M-10A1 image). The constant demand of tank destroyers for the battlefields led to the request to Ford Motor Company for the start-up of a second production line. Thus, from October 1942 to September 1943 Ford built 1,038 vehicles under designation M-10A1. This new vehicle had some differences with the M-10, mainly the hull, which was taken from the M-4A3 Sherman medium tank. The engine was different too, because it was a gasoline type instead of a diesel one.(M-10A1 image). The M-10A1 GMC had a Ford GAA V-8 petrol engine that produced 450 hp and had better performance than the M-10 GMC’s engine. It was lighter and more powerful, though with less torque, and its installation forced to mount an exhaust grille below the armor at the rear of the vehicle and larger grill doors atop the rear hull.(M-10A1 image). Although most of M-10A1 were built by Ford, Fisher Tank Division built 375 complete vehicles and 300 chassis. In January 1944, a new turret with a 90mm gun was installed on these 300 chassis, which would be designated as M-36 tank destroyer. Altogether the amount of M-10A1 produced was 1,713, including the M-36‘s chassis. Due to their gasoline engine, the M-10A1 fleet was not sent to the European Theater and was relegated to instructional tasks within the United States. From January to June 1944, more than 200 vehicles were transformed to M35 Prime Movers to tow 203 and 240mm heavy artillery pieces.The M-10 baptism of fire occurred in the North Africa deserts against the German Afrika Korps at the end of March 1943. These new vehicles served in part to change the opinion of some American commanders about the effectiveness of tank destroyers during combat. This opinion was more than justified if we observe the poor performance of the American models sent there to date, the 37mm M-6 and the 75mm M-3 halftrack. The M-6 was a simple off-road jeep vehicle with an almost obsolete gun and the M-3, although better armed did not have the mobility or the minimum protection required.The M-10 had to face from the beginning the distrust of many commanders who preferred the use of tanks. Of course the tanks were much more expensive and usually had a worse mobility due to their greater weight. For example, the price of an M-10 manufactured in September 1942 was $ 47,905, while an M-4A2 Sherman tank cost $ 60,215. Likewise, the wrong use, such as assault guns or accompanying the infantry, also did not help the vehicle demonstrate its full potential.The controversy over the use or not of the M-10 reached such a point that it was decided to convert 15 self-propelled anti-tank battalions in towed anti-tank gun battallions. In these units the tank destroyers were changed by 76mm towed guns, which put even more pressure on the utility of the M-10 units. The main problem was that they were not used with an adequate doctrine. In Italy, the lack of enemy tanks in the area, prevented them from being used for what they were created. They were usually used as assault guns, and even as self propelled howitzers! Where the M-10 were squeezed to the maximum was after the Invasion of Normandy. In France the M-10 was the only American vehicle capable of destroying German tanks at a safe distance. Its use became essential, and logically its weak points became more evident. For example, the roofless turret prevented them from leading the advances on villages or wooded areas, something quite usual in France. Of course its firepower was much appreciated by the infantry, especially to destroy bunkers and machine gun nests with the HE M42A1 round.As the Normandy campaign progressed, the M-10 gained a good reputation relegating the towed anti-tank Battallions to secondary or defensive tasks. According to some studies, it was found that each antitank self-propelled battalion destroyed an average of 22 tanks and 23 pillboxes while the antitank towed battallions only destroyed an average of 6 tanks and 4 pillboxes.It was during the Ardennes Offensive when the M-10 GMC could be used for the first time as the doctrine indicated. For the first time, (and last), these tank destroyers were able to fight against an “avalanche” of German tanks. In spite of not being used in large concentrations, they were decisive in containing the German advance over St. Vith and Bastogne, vital points for the German campaign. This was the final examination and they approved it amply.As the War progressed, M-10 Battalions lost their use as reserve forces and were commonly assigned to the Infantry Divisions. Then, they usually separated them into companies that were sent to support the First Line Regiments or Battalions. This totally contradicted the use tactics imposed by the Tank Destroyer Center, but in these support missions is how the M-10s won the appreciation of the troops, especially in the tough advance on Germany.There was something counterproductive within the US Army with the expansion of the tank destroyers. It was thought that it was enough with the M-10 to fight the enemy tanks, so the development of the American tanks suffered break. Unfortunately the first encounters with the new German Panther tanks in Normandy taught the Americans the wrong way of thinking, because neither the M-10 GMC managed to stop the advance of the Panthers most of the time.In June 1944, “IKE” himself confirmed that the 76 mm gun could not destroy the new Panther tanks at safe distances. This conclusion lead tothe urgent develop a new tank destroyer with a 90mm gun installed. The M-10 losses were increased progressively as it was advancing on Germany. In February 1945, the peak of losses was reached, when 106 M-10s out of a total of 686 operatives were lost. Overall, from June 1944 to May 1945 550 Americans M-10 were lost in combat. (M-10 “Sonic Tank” image). At the end of the WWII a curious use arose for some M-10 tank destroyer. Here we see an M-10 that has installed an amplifier and a loudspeaker. This vehicle belonged to the 3313th Signal Service Company from the Signal Corps, which were units designed to serve as a decoy and attract enemy forces to them leaving the way clear to other units. Sounds of engines, mechanics, orders and related to motorized and armored units in motion were emitted through the loudspeaker. These units were commonly known as “Sonic Companies.”There were M-10 deployed in the Pacific, where they did not have the same success as in Europe. Here the tank destroyers were always used in support of the infantry due to the lack of enemy tanks. They had to carry out the support missions protected by the infantry and at safe distances, because it was evident that these vehicles were especially vulnerable to the almost suicidal Japanese anti-tank tactics.After WWII, it was decided to close the Tank Destroyer Center because it was obvious that tank destroyer missions could be carried out with the tanks in service in a more effective way. It can be said that during war nobody paid attention to the specific tactics for the M-10s, since they ended up exercising as medium tanks, assault guns and even self-propelled artillery, roles for which specific vehicles already existed. However, some armies kept them in service for a few more years.
