Do you think the USSR and Eastern Europe were free from the tendencies of capitalism to create imperialist war? The only post-WWII wars in Eastern Europe were skirmishes by capitalist-funded nationalists (quasi-fascists) and the civil war in Yugoslavia exacerbated by NATO to balkanize the country. The wars that the USSR supported were all pre-existing national liberation movements against imperialist colonizers, and they nearly always entered after imperialists had thrown massive resources into oppression. For example, Vietnam.