In Yalta conference of 1943, the four D’s (disarmament, demilitarization, de-nazification and division) for Germany was decided and thus, Germany was divided into four zones. At Potsdam though, in the Potsdam conference of 1945 the agreement at Yalta proved to be hard to be enforced and finally the countries decided that they would carry out the de-nazification of Germany in their own ways in their respective zones of occupation. As agreed at Potsdam, Germany was then divided into four zones and so was Berlin. Thus the whole country of Germany and its capital was divided between four countries, that is, France, Britain, Soviet Union and USA; thus making Germany the focus during the early cold war period.
The Czech coup of 1948 convinced the west that they must resist Stalin, which gave rise to the policy of containment of communism by the USA. The west forces and the West Berliners had to rely on receiving food and supplies from the western countries delivered along road, rail and air corridors. However, in March 1948, Stalin started putting a stranglehold on western interests in West Berlin, through transport restrictions. Stalin began the total blockade of Berlin on June 1948. The road, railways and canals linking West Berlin to the western sector of Germany were all closed. This helped to accentuate the difference between the personalities of Stalin and Truman. The supply of electricity from east to West Berlin was also cut. This is regarded as the first crisis of the cold war and direct military confrontation became a possibility but the west rather opted to supply Berlin from air; which is the Berlin Air-lift. This made clear that the agreement between the US and USSR would be very difficult if not impossible. The failure of the blockade led to the division of Germany as the west moved quickly to form the Federal Republic of Germany (FDR) and in response, the soviets set up the German Democratic Republic (GDR) in the Soviet occupation zone. Thus, Germany was divided into two countries in the year 1949 and the four-power control of Berlin continued. The need for a US defence commitment was emphasized by the Berlin Airlift and Czech coup, which resulted in the formation of NATO (North Atlantic Treaty Organisation) in 1949 between USA, Canada and the Brussels pact powers, that is, Norway, Denmark, Iceland, Italy and Portugal. Afterwards, in 1954, West Germany was admitted into NATO, which conformed the Soviet fear and the Soviet Union denounced the formation of Warsaw Pact. This caused the division of Europe into two power blocs. Thus, the concentration of activities in Germany and their impact in the development of cold war made it clearly the focus at that time.
The division of Germany into East Germany (GDR) and west (FDR) had many consequences as economic and political differences existed in the two Germanys. The west had received the Marshall aid whereas the east had not, thus the East Germans wanted to move towards to the west. Besides that, east was authoritarian and a Stalinist state whereas west was not. As a result of these differences, any attempt to reunite Germany seemed futile. After the Berlin blockage, Berlin remained divided under joint American-British-French-Soviet occupation and the economic and political inequalities of the two Germanys could easily be seen in the difference between east and West Berlin. West Berlin appeared to be dynamic example of capitalism. Thus, people of the east wanted to move to the west. This exodus of young and skilled East Germans-which was encouraged by the west –meant that between 1945 and 1961 about one-sixth of the whole German population took the opportunity to move towards the west via West Berlin. Thus, the massive exodus of people also made Germany the focus of the early stages of hostility in the cold war.
In 1958, Khrushchev proposed a peace treaty that would recognize the existence of two Germanys. This demand for demilitarization of Berlin and withdrawal of western troops gave rise to the Berlin crisis of 1958.the tension was growing in Berlin and the number of refugees entering west increased. Thus, in August 1961, barbed wire was erected between east and West Berlin which later on took the form known as the Berlin Wall, this stood as a symbol for the division of Germany and also for the conflicting ideas of differencing ideologies, communism and capitalism.
Therefore, Germany was the focus of the cold war hostility between 1945 and 1961 as it was the representation of power and the concentration of activities. It was also he hub of conflict between differing ideologies, communism and capitalism and personalities, Stalin and Truman (and later, Eisenhower and Khrushchev; Kennedy and Khrushchev). Berlin blockade and later that division of Germany followed by the creation of Berlin Wall made Germany the peak of ideological differences at this period. Thus, I believe, Germany was the focus of cold war hostility during 1945 to 1961 considering the huge amount of the concentration of activities and conflict in that time period.