The next post covers the Cold War Era and as such has some overlap over the last two posts. I wasn't sure if I wanted to do it that way, but that's how the museum is arranged, so here goes.
There is some discussion about when the Cold War actually began. Some people could make the argument that it began in Feburary 1945 when the Yalta Conference was held. It was decided that Europe would be split into two parts. One part under the influence of the Soviet Union, the other under the influence of the Western allies. Stalin was intensely distrustful of the United States and Britain (and vice versa I would imagine) and thought that the western invasion of Europe was delayed to weaken his forces. The decision to split Europe led to the Communist Eastern Europe and the non-Communist Western Europe.
Other people may make the argument that it began at the Potsdam Conference which was held later in the year. This was held after the death of Roosevelt, so it was Truman, Stalin and Churchill at first. Churchill was ousted and he was replaced by Atlee. Since Stalin were the more experienced leader, it is said that many concessions were made by the inexperienced western leaders. The Potsdam conference solidified the Soviet hold on Eastern Europe.
Some people may even make the conclusion that the Cold War didn't start until 1949, when the Soviets detonated their first atomic bomb. This sort of restored a balance between the two powers.