How far was Stalin responsible for the start of the Cold War by 1949?

1- Analyse and evaluate arguments that would corroborate this statement:Stalin's desire for security and a 'buffer zone' in Eastern Europe, leading to his implementation of communists governments in the Eastern Bloc. This clashed with Western 'Wilsonian Liberalism' and a desire for open democracies in these countries, however the USSR/Russia had been attacked three times from the West in that century and it could be argued the US didn't understand this fundamental desire for security, especially given Stalin raised his desire for security as early as 1943 in Tehran.1946 Bolshoi Speech=belligerent and suggested peace between East and West not possible.Stalin's violation of the Potsdam agreement for open elections in Eastern Europe and the fact that the Red Army had not left the countries it liberated from Nazism.2- Analyse and evaluate counter arguments- eg. that the West was responsibleTruman, The Truman Doctrine, 1947, and his 'Iron Fist' policy was openly confrontational towards communism- however he only sought containment and not outright conflict.Marshall Aid, 1948, was seen by Stalin as 'dollar imperialism' and appeared to divide Europe into two campsSecrecy over the atomic bomb and refusal to let the USSR join in the occupation of Japan, as had previously been agreed.Churchill's bellicose speech at Fulton, Missouri3- Conclusion- weigh up evidence and give an opinion as to which argument is more valid and convincing.