As the Second World War progressed, the Soviets were fielding better and better tanks. The Finnish Army, on the other hand, had to make do with a large number of captured tanks, which were for the most part lightly armored and armed. The Finns decided to redesign the BT-7 Model 1937tank. They constructed a new turret and armed it with British-made 114.3 mm howitzers that had been supplied by the British during the Winter War. Eighteen BT-42 were built and these were pressed into service in 1943. These converted vehicles quickly became very unpopular with their crews. The weaknesses could mainly be attributed to the new turret, which apart from giving the tank a high-profile also added significant weight to the vehicle, stressing the suspension and the engine. The BT-42 was used for the first time in 1943, at the Svir River, where it was used against enemy pillboxes. The design worked reasonably well against soft targets but was completely unsuitable for anti-tank warfare. To counter this, the Finns copied a German-designed HEAT round for the gun and it was initially thought that it would be effective against the sloped armour of the T-34. However, problems arose with the copied HEAT shells fuses, which apparently did not arm themselves correctly after firing, due to the different muzzle velocity and round spin rate of the 4.5 inch howitzer compared to the original German guns. The BT-42s were used again during the major Soviet offensive in 1944. They were deployed in the defence of Vyborg. In one encounter, a Finnish BT-42 hit a Soviet T-34 18 times, failing even to immobilize the enemy vehicle, as this vehicle's fuses failed to work correctly. Eight of the 18 BT-42s in action made no significant contribution to the fighting. At the time Finnish armored units were still composed mostly of older designs such as the Vickers 6-Ton, T-26 and T-28 tanks, and all of these suffered losses. Emergency supplies of Panzer IV tanks and StuG III self-propelled assault guns from Germany, as well as captured T-34s, made it possible for the Finns to replace its losses with more effective vehicles. The BT-42 was retired soon after the Vyborg battles, replaced in their intended role by German-made StuG IIIs.
