The BT-42, officially known as "15 tonnin rynnäkkötykkipanssarivaunu BT-42 (15-ton assault gun tank BT-42)", was a modified variant of the Soviet BT-7 light tanks which were captured by Finland during the Winter War and Continuation War; due to the lack of firepower of the 37/45 mm gun on original BT tanks and the dire need for tanks to defend against Soviet forces, some of these BT tanks were then upgraded with a British-aided 4.5 inch howitzer and new turret that housed this very gun. These tanks were then deployed to the battle against Soviet forces; only one of these 18 tanks eventually survived the war and the subsequent scrapping of the surviving tanks.

The BT-42, introduced in Update "Fire and Ice", is perhaps one of the most iconic light tanks in Finnish service as well as being a "meme" tank among players due to its screen time in a Japanese animation film. This captured BT-7 modified with a huge QF 4.5 inch howitzer will strike fear into enemies with its fearsome firepower while still retaining the iconic fast and nimble playstyle of a BT light tank.