Soviet soldiers with a 76-mm divisional ZIS-3 anti-tank gun firing on a street of Budapest, Hungary (the modern location of the place - Üllői út a Kinizsi utca felé nézve); January, 1945.
ZiS was a factory designation and stood for Zavod Imeni Stalina ("factory named after Stalin").

Anti-tank gun in city

A column of Hungarian soldiers captured by Red Army units near Lake Balaton, Hungary. Photo taken in the town of Balatonalmádi, also in Hungary; April, 1945. 

Into uncertain fate...

A Soviet 52-k gun and crew engaged in battle on a street of Budapest, Hungary; January 1945.  
The 85 mm gun M1939 (52-K) was a Soviet anti-aircraft gun. In emergencies, as here, they were utilized as powerful anti-tank weapons. 