The Cold War started operating on the ground level with the announcement of the Truman Doctrine in March 1947.
The immediate purpose was to help the non-communist governments in Greece that Bulgaria, Albania and other communist countries wanted to out.
In the Truman Doctrine it was clearly stated that the USA would help every independent country to maintain its independence from all external influence.
In reality the Truman Doctrine emphasized as follows: (1) American intervention into the free countries if they were threatened by ‘totalitarian regimes’.
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(2) the assistance promised by the USA to the weaker powers were in fact an attempt to bring them closer to the USA.
(3) The Truman Doctrine also was a reply to the formation of the Soviet Bloc forming a security ring round the Soviet Union.
The Truman Doctrine that was announced by the American President was criticized by the Soviet Union and her allies.