<P> The entire Soviet delegation rose and walked out . Truman later noted, "For most of Germany, this act merely formalized what had been an obvious fact for some time, namely, that the four - power control machinery had become unworkable . For the city of Berlin, however, this was an indication for a major crisis ." </P> <P> On 25 March 1948, the Soviets issued orders restricting Western military and passenger traffic between the American, British and French occupation zones and Berlin . These new measures began on 1 April along with an announcement that no cargo could leave Berlin by rail without the permission of the Soviet commander . Each train and truck was to be searched by the Soviet authorities . On 2 April, General Clay ordered a halt to all military trains and required that supplies to the military garrison be transported by air, in what was dubbed the "Little Lift". </P> <P> The Soviets eased their restrictions on Allied military trains on 10 April 1948, but continued periodically to interrupt rail and road traffic during the next 75 days, while the United States continued supplying its military forces by using cargo aircraft . Some 20 flights a day continued through June, building up stocks of food against future Soviet actions, so that by the time the blockade began at the end of June, at least 18 days supply per major food type, and in some types, much more, had been stockpiled that provided time to build up the ensuing airlift . </P> <P> At the same time, Soviet military aircraft began to violate West Berlin airspace and would harass, or what the military called "buzz", flights in and out of West Berlin . On 5 April, a Soviet Air Force Yakovlev Yak - 3 fighter collided with a British European Airways Vickers Viking 1B airliner near RAF Gatow airfield, killing all aboard both aircraft . The Gatow air disaster exacerbated tensions between the Soviets and the other allied powers . Internal Soviet reports in April stated that "Our control and restrictive measures have dealt a strong blow to the prestige of the Americans and British in Germany" and that the Americans have "admitted" that the idea of an airlift would be too expensive . </P>

Why was west berlin considered the heart of the cold war