Which were the most important causes of the Cold War?

Question: Which were the most important causes of the Cold War!?
Best Answer - Chosen by Asker:

The proximate cause was the Soviet Union's unwillingness to live up to its agreements at Yalta!. However, it does back to that conference, when the naivete of Roosevelt about Stalin's intentions encouraged him to ignore previous agreements!.
These primarily were to hold democratic elections in Poland, Hungary, Czecholslovakia, Bulgaria with Allied supervision!.
Another reason was the USSR's refusal to withdraw and demobilize its forces from Germany/E!. Europe after the war!. It was seen, rightly, that these were now an occupation army!. (However, part of the reason was the primitive Soviet infrastructure-it was easier to keep manpower in the Army instead of trying to ship them back, and find employment for them; the Soviet economy was devastated until 1960 or so!.) Since the US was demobilizing as fast as possible, the UK and France were no help after the war, there was fear that the Red Army would advance at any time and occupy all of Europe!.
Post-Soviet archival research, does give some credence to that fear!. If Stalin thought he could get away with it-he would've done it; but the necessity to rebuild the USSR and fear of US atomic retribution kept him at bay!.Www@QuestionHome@Com

There was really only one cause: the Soviet Union's expansionist ambitions!.Www@QuestionHome@Com

the policies of the two nations involvedWww@QuestionHome@Com

Communist expansion, and the efforts of the U!.S!. to curb it!.Www@QuestionHome@Com