TBH, we could write an entire Shmoop-ography of Joseph Stalin and probably wouldn't get to cover everything about him. But in the context of our little story about Harry and his doctrine, we need to consider the not-so-fun facts about the totalitarian leader/ ruthless dictator of the Soviet Union.
Everyone in Washington—and we mean everyone, from FDR to Truman to Clifford—liked "Uncle Joe" Stalin and thought we would get along with him splendidly after the war.
Unfortunately, things didn't exactly work out that way.
By 1947, Stalin had:
The whole thing was like the Batman v Superman movie: everyone got all excited looking at the preview, but once the Western powers sat down and saw the entire picture, they wanted out as soon as possible.
In the context of Truman's speech, Stalin is "an aggressor" and leader of a "totalitarian regime."
Hogwarts House: 100% Slytherin—need we say more?