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3-in Gun Motor Carriage MIO |
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During the late 1930s and early 1940s the US Army formulated a novel tactical doctrine, whereby fast-moving armoured formations were to be countered by a new tank destroyer force comprising towed and self-propelled high-velocity anti-tank guns. This tank destroyer force was to be used en masse and was to be armed with powerful guns, and one of the first operational results of this doctrine was the Gun Motor Carriage MIO selfpropelled mounting armed with a 76.2 mm (3-in) gun known as the M7, a development of an anti-aircraft weapon. The secondary armament was one 12.7-mm (0.5-in) Browning machine-gun. The MIO used the main chassis of the M4A2 medium tank (the Sherman) allied to a new thinly-armoured upper hull and an open-topped turret. The relatively thin armour of the hull was improved by the use of sloping armour plates to increase protection, and sloped armour was also used on the turret. Unlike many other tank destroyers of the time the MIO had a turret with 360° traverse, for although the MIO was intended for use as a tank destroyer it was seen by the US Army as a gun earner and was not intended for close-order combat, hence the relatively thin armour. The gun was quite powerful for the period it was introduced. Production commenced during September 1942, and such was the potential of American industry that when production ceased in December 1942 4,993 had been produced, The bulk of this total went to US Army tank destroyer battalions, and in early 1943 there were 106 active battalions. But as the war continued their number gradually decreased when it was realized that the tank destroyer concept as an arm separate from the rest of the American armoured forces was wrong and as it emerged that the best counter to a tank was another tank. But the tank destroyer force remained in being until the war ended, most of the battalions being used in Europe. By the end of the war many of the M 10s and their associated equipments and towed guns were being Above: The American MIO was designed to be the main weapon of the Tank Destroyer Command's mobile units, and mounted a 3-in (76.2-mm) gun in an open-topped turret. The armour protection was relatively thin, as the weight of better armour was sacrificed for all-round performance and speed once in action. used more as assault forces than tank destroyers. The MIO was the primary equipment of these battalions and was used not only by the US Army but by the British (who knew the MIO as the Wolverine) and later by the French and Italian armies. In combat the MIO proved to be less than a complete success, for despite its thin armour it was a large and bulky vehicle and as time went on the gun lost much of its antiarmour effectiveness. But the M 10s were still in use when the war ended. By then the British had re-gunned many of their M 10s with 17-pdr guns and re-named the type Achilles, The MIO had in the meantime been joined by the M10A1, which was the same vehicle but using the chassis of the M4A3 medium tank with its different engine installation and some other changes. The M 10s were used in battalions, each with around 36 M 10s and with strong reconnaissance and antiaircraft elements, By early 1945 most of the tank destroyer battalions were distributed among the more conventional armoured formations, and were then used exactly as other armoured formations and the exclusive tank destroyer concept died. Specification MIO Crew: 5 Weight: 29937 kg (66,000 lb) Powerplant: two General Motors 6- cylmder diesel engines each developing 276,6 kW (375 hp) Dimensions: length overall 6.83 m (22 ft 5 in); width3.05 m (10 ft); height 2.57 m Latein the war theMlO(left) was supplemented by theM36 (right), which useda90-mm (3.54-in) gun, still in an open-topped turret. The M36 was designed as early as 1942 but took a long time to get into production, so that it was late 1944 before the first of them reached Europe. By then they were mainly used as assa ult guns. (8 ft 5 in) Performance: maximum road speed 51 km/h (32 mph); road range 322 km (200 miles); gradient 25°; vertical obstacle 0.46 m (18 in); trench 2.26 m (7 ft 5 in); fording 0.91 m (3 ft)
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