The soviets as an entity are a ghost of just how piss poor the Russians transitioned as an state in the late 19th/early 20th century that springboarded off the first world war.
What film was the first I don't have a clue, but as early as the 1937 Peter The Great (technically not medieval but almost), you had crowds of filthy oppressed peasants. And that slav cynicism was already in western movies by the 50s by looking at the seventh seal.
