The World War ended in 1945 but with the end of the war the friendship between the capitalists and communists also came to an end .The friends of war period became opponents after the end of the war. The first step in this direction was taken by the Feb speech of Stalin. In this speech he declared that the communism would not remain limited to Eastern Europe only and communist revolution would be organized throughout the world. This declaration of Stalin alarmed the capitalist countries and the suspicion between them got transformed into cold war.
In March 1946 Winston Churchill made a famous speech in USA and asked the capitalist countries to come together in their fight against communism. He proclaimed that war has not ended but it had assumed a different shape and the capitalist countries must be prepared to fight against communism. He also proclaimed the concept of Iron Curtain. During 1946-47 the Soviet Union had successfully captured many parts of Eastern Europe and Communist governments were installed in number of countries such as Romania, Bulgaria, and Czechoslovakia and Yugoslavia. The success of communism in these countries alarmed the western countries even further.
In 1947 American President Harry Truman proclaimed his Truman Doctrine which said that USA would support all the democratic forces against communism throughout the world. This doctrine was applied during Greece Civil War (1948-49) where the supporter of communism and supporters of capitalism were supported by USSR and USA openly. This was the first military campaign of cold war period. It had brought the opposing ideologies to the battlefield against each other. But the scope of war remained limited to Greece only.
In June 1947 Marshall Plan was announced by the US secretary of state, George Marshall. This plan was also European Recovery Program. It was based on the understanding that communism was less likely to thrive in prosperous societies.USA announced a massive aid of 13000 million dollars to Europe for economic recovery. The aid for all the countries of Europe but only the capitalist countries of Western Europe accepted the aid and communist countries of Eastern Europe were not allowed to accept the aid by USSR. The Marshall Plan was immensely successful and it resulted in the economic recovery of Western Europe. It also made the division of Europe inevitable as after the economic recovery the western European countries became prosperous. Due to economic differences, the soviet leadership faced day to day humiliation and decided to stop all kind of communication links between Eastern and Western Europe. It led to the further division of Europe into two parts.
In September 1947 the soviet leadership established Comminform (communist information bureau).The objective of this bureau was to establish the soviet pattern of political government in all the countries. When the Soviet Union and the capitalist countries of West failed to reach on an agreement over the issue of peace treaties, Germany was divided into four parts and one part was given to each major power. The capital of Germany Berlin was located in the area given to USSR. The communist controlled areas remained economically backward and it was being seen in Berlin. To overcome the humiliation the Soviet leadership planned to oust the capitalist forces from western part of Berlin and to achieve that objective the road links between the capitalist controlled Germany and the capitalist controlled Berlin were severed.
The Soviet move gave birth to a serious crisis but the capitalist forces continued to supply the necessary commodities to the part of Berlin controlled by them. The blockade remained for one year and in May 1949, USSR realized the failure of tactics and blockade was removed. The Berlin blockade intensified the cold war and brought the communist and capitalist blocks on the verge of open war. The capitalist countries remained aggressive in their anticommunist policies.
The lessons learned from a Berlin blockade forced the western powers to come together and adopt the system of collective security. This resulted in the formation of NATO in April 1949. After the failure of Berlin blockade the soviet leadership tried to follow the policy of economic development in East Europe as well. USSR announced Molotov plan but it could not succeed as Marshall Plan because the amount of aid given was very less and implementation was far from perfect. In September 1949 USSR emerged as nuclear power and tactical edge enjoyed by the capitalist block was erased.Infact tactical balance was shifted to the side of USSR. This further intensified the cold war.
In October 1949 the communist revolution was successfully completed in China and the emergence of Sino-Russian alliance intensified the cold war further. The Korean War (1950-52) was another manifestation of the intensification of cold war. This war was fought between the communist and capitalist elements actively supported by each block.