I don't think that the Soviets are the primary culprit in the Cold War, as the Containment narrative asserts. I think during the Stalin period the United States portrayed more aggressive tendencies towards the USSR than the other way around. Following the territories assimilated into either the USSR proper or its sphere of influence, their expansion was rather limited. The entire idea of Soviet expansionism was for the most part a propaganda campaign.

Look at the Berlin Blockade, one of the first acts of the Cold War. This was a response to the Marshall Plan and perceived Western separatist policies in American-controlled West Berlin. Upon discovering that the Plan would require economic cooperation, Stalin rejected it and actively attempted to subvert it from the Paris talks (this is confirmed by the diary of French president Vincent Auriol, and it is common knowledge that Molotov completely rejected it). The Soviets viewed the Marshall Plan as an attempt by the Americans to gain influence and perhaps even control over countries accepting payment. Andrei Vyshinsky openly stated this in a speech to the UN General Assembly in September 1947:

The so-called Truman Doctrine and the Marshall Plan are particularly glaring examples of the manner in which the principles of the United Nations are violated, of the way in which the organization is ignored.

As the experience of the past few months has shown, the proclamation of this doctrine meant that the United States government has moved towards a direct renunciation of the principles of international collaboration and concerted action by the great powers and towards attempts to impose its will on other independent states, while at the same time obviously using the economic resources distributed as relief to individual needy nations as an instrument of political pressure. This is clearly proved by the measures taken by the United States government with regard to Greece and Turkey which ignore and bypass the United Nations as well as by the measures proposed under the so-called Marshall Plan in Europe. This policy conflicts sharply with the principle expressed by the General Assembly in its resolution of 11 December 1946, which declares that relief supplies to other countries 'should (...) at no time be used as a political weapon.'

As is now clear, the Marshall Plan constitutes in essence merely a variant of the Truman Doctrine adapted to the conditions of postwar Europe. In bringing forward this plan, the United States government apparently counted on the cooperation of governments of the United Kingdom and France to confront the European countries in need of relief with the necessity of renouncing their inalieable right to dispose of their economic resources and to plan their national economy in their own way. The United States also counted on making all these countries directly dependent on the interests of American monopolies, which are striving to avert the approaching depression by an accelerated export of commodities and capital to Europe (...)

It is becoming more and more evident to everyone that the implementation of the Marshall Plan will mean placing European countries under the economic and political control of the United States and direct interference by the latter in the internal affairs of those countries.

Moreover, this plan is an attempt to split Europe into two camps and, with the help of the United Kingdom and France, to complete the formation of a bloc of several European countries hostile to the interests of the democratic countries of Eastern Europe and most particularly to the interests of the Soviet Union.

An important feature of this plan is the attempt to confront the countries of Eastern Europe with a bloc of Western European states including Western Germany. The intention is to make use of Western Germany and German heavy industry (the Ruhr) as one of the most important economic bases for American expansion in Europe, in disregard of the national interests of the countries which suffered from German aggression. The "measures taken by the United States government with regard to Greece and Turkey" that he is referring to is the famous Truman Doctrine, announced in a speech on March 12, 1947, prior to the Berlin Blockade and foreshadowing the events to come. It is commonly cited as the start of the Cold War.

It is clear that the Soviets perceived the Marshall Plan as aggressive American expansionism into Western Europe. What this means is that the Berlin Blockade was the result of a build up on both sides, and not an act of Soviet aggression against West-German and American victims, as is commonly perceived.

In March 1948 Truman unknowingly summed up the position of both sides when he said that "The situation in the world today is not primarily the result of the natural difficulties which follow a great war. It is chiefly due to the fact that one nation has not only refused to cooperate in the establishment of a just and honorable peace but—even worse—has actively sought to prevent it."

The Marshall Plan ("Economic Cooperation Act") was signed into law on April 3, 1948, which is around the time that the events surrounding the Berlin Blockade started. The Blockade itself officially commenced shortly thereafter.