 Soviet 50-mm company mortar, model 1940 during the battles in Stalingrad; December 18, 1942.

Light Infantry Mortar

Red Army soldiers on the march with horse-drawn 76-mm ZiS-3 divisional cannons. Presumably, the picture was taken during the Balaton operation in Hungary; March 1945.
The ZiS was a factory designation, that stood for "Zavod Imeni Stalina" (Plant named after Stalin), the honorific title of Artillery Factory No. 92, which first constructed this gun.

Relying on animal power

Soviet 82-mm mortar team is firing round after round at German Forces in Stalingrad; October 20, 1942.