This question is wide open to interpretation and discussion. I am not entirely certain that you will obtain much in way of consensus. I think that there are some important events, but in the end, I think that you are going to have to assess for yourself what you consider to be the most important events that end up shaping the Cold War and how they fit on your timeline. Certainly, I think that one significant event was the end of World War II and the different conceptions of the world that the Soviet Union and the Americans held towards the world. Along with this would be the construction of the Eastern Bloc, a move that physically ended up creating a line of demarcation as to where the sides in the Cold War would be established. Churchill's "Iron Curtain" speech would have to be significant in that it gave the vocabulary to all people in understanding the Cold War conflict. I think that these events are important because they end up establishing the paradigm of the Cold War. I think that the Korean War could be seen as significant because it demonstrated the first real moment that American containment was seen as the driving force behind all foreign policy, showing to what ends America would go to stop Communism. Along these lines, I would also add the Cuban Missile Crisis as another significant event in the Cold War, for it helped to show how both nations featured both a strong disdain for the other side, but also helped to show how individual leaders in both nations were heavily influenced by their hard-line constituencies from a domestic point of view.
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