BT-42

The BT-42 was a Finnish assault gun, constructed during the Continuation War. It was constructed from captured Soviet BT-7 light tanks and British 4.5-inch howitzers (114 mm-calibre light howitzer, model 1908) from 1918, which had been donated during the Winter War. Eighteen  vehicles were constructed, yet only 1 survives to this day, housed at the Parola Tank Museum.

Development and use
As the Second World War progressed, the Red Army 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 1937 tank. They constructed a new turret fitted with 76 K/02 gun sights and armed it with British-made 114.3 mm howitzers that had been supplied by the British during the Winter War (Q.F. 4,5 inch howitzer Mark II, also known as 114 Psv.H/18 in Finland). 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.

The BT-42 ended up ultimately failing at the original goal to have some sort of domestic armour production to combat the Soviet one this being realised when the tank became utterly ineffective in tank-tank combat and later replaced with the German lend leased Stug IIIs.

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. Nine BT-42s were deployed in the defence of Vyborg. In one encounter, a Finnish BT-42 hit a Soviet T-34 eighteen times, failing even to immobilize the enemy vehicle. During this battle a BT-42 was destroyed by a T-34 tank shell. Seven of the BT-42 tanks were also lost due to mechanical failures, resulting in eight of the nine deployed being destroyed. At the time Finnish armoured 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 made it possible for the Finns to replace their losses with more effective vehicles. The BT-42 was retired soon after the Vyborg battles, replaced in their role with German-made StuG IIIs. Finland also used captured T-34s, as well as receiving more of these vehicles from Germany's stock of captured enemy kits.