A Red Army mobile 82mm Mortar on a Harley Davidson motorcycle.  It was an ingenious and effective mode of rapid firepower deployment...

Sidecar Mortar!

A battery of Soviet 122mm M-30 howitzers firing at the enemy (=Germans) in Budapest, Hungary; January 2, 1945.

Artillery action in the city

Battery of Soviet 76-mm F-22 (USV) cannons on the Kalinin front; 1942-43.
  The Kalinin Front was a major formation of the Red Army active in the Eastern Front of World War II, named for the city of Kalinin.