I'm going to say something controversial (at least here), but this is my observation/analysis of history. Russians, in general (and this includes the Soviets) DO NOT LIKE WAR. They avoid it if at all possible, until you attack/provoke them (then they turn into a monster). The USSR allied with Germany when it looked like that would allow them to avoid being in the war. Not ideologically pretty, but fairly rational. Hitler turning on the USSR was one of the critical mistakes leading to his defeat (which the USA is quick to take full credit for, even though Russia sacrificed millions of people for it).
Throughout pretty much all of (relatively) modern history, this pattern has held, and most of the Cold War Soviet "expansionism" was explicitly provoked (see Z. Brzezinski's successful plan to provoke the USSR into invading Afghanistan). For goodness' sake, the Tu-95 "Bear", the "most feared" Soviet/Russian long-range bomber first flew in 1952, and had its combat debut in Syria in November 2015! This is not the pattern of a warmongering, expansionist people.
Non-aggression Pact between USSR and Germany was anything but alliance. The very name of the pact clearly hints it.