From the article:
Soviet Red Army tank units often had a battery of these self-propelled guns attached for added firepower against enemy infantry and guns. The 76mm gun of the BT-7A artillery tank provided the ideal firepower for this work. This modification of the BT-7 fast tank mounted a short 76mm howitzer that fired a powerful high-explosive round. While the other BT fast tanks would deal with the enemy tanks, the BT-7A artillery tank would knock out anti-tank guns and defending infantry.