The orthodox school sees the Cold War as the product of the aggressive and expansionist foreign policies of USSR. This view has been presented by historians such as W. H .McNeill, H. Feis, and A. Schlesinger.
After WW2 a power vacuum was left in a large part of central and Eastern Europe. Stalin took the advantage of this in order to strengthen the Soviet Union and spread communism. In the Yalta conference (Feb 1945), Stalin demanded parts of Poland to be given to USSR. Stalin made a communist government of Poland although there was already a Polish government in UK. This kind of behavior made the West (USA, UK etc) fear that USSR would gain permanent control over Poland. Stalin went even further, in the same year (1945 July~August) Potsdam conference, Stalin wanted parts of Turkey, demanded trusteeship of one of the former Italian colonies in Africa, disabled USA and allies access in areas of Europe occupied by the Red Army, moved the frontier of the USSR westwards and gave Poland lands that the allies didn't agree.
Stalin's actions and his wants made the West think Stalin was trying to make a huge communist empire. This marked a cooling in relations between the two sides.
Between 1945 and 1948 communist regimes were established throughout Eastern Europe (Salami tactics). Albania (1945), Bulgaria (1945), Poland (1947), Hungary (1947), Romania (1945-1947), Czechoslovakia (1948), and East Germany (1949), all these countries went through a different process, but the results were the same. The Red Army retained a presence in much of Eastern Europe during and after this process. A 'communist zone' was created in Europe. This was seen as yet another example of Stalin's expansionist foreign policy. The Berlin blockade could be another example, 24th June 1948; Stalin closed all rail and...