One of the earliest "hot spots" in the Cold War was in the European city of what

One of the earliest "hot spots" in the Cold War was in the European city of Berlin, Germany. This was due to the Berlin blockade by the Soviet Union in 1948.

Explanation:

The Berlin blockade went from June 23, 1948 to May 12, 1949, during which the western sectors of Berlin were supplied from the air by the Berlin Airlift.

On June 20, 1948, the Western Allies - after unsuccessful consultations with the Soviet Union - carried out a monetary reform in the western occupation zones of Germany (which, according to the original plans, was not to apply to Berlin due to its quadruple status). On 23 June, monetary reform was also carried out in the Soviet occupation zone, and the new eastern mark was to apply to the western sectors of Berlin as well: to achieve the financial and economic tying of the western sectors to the Soviet zone. The Western Allies therefore introduced the Western Mark in their Berlin sectors as well.

On the night of June 23 to 24, the Soviet command in Berlin responded by cutting off electricity supplies to the western sectors and, a few hours later, closing all land and water access roads. Initially, the Allies were not even united in their future policy towards Berlin. Eventually, the American military governor of the city, Lucius D. Clay, gave the order to establish an air bridge (air corridors were not blocked).

Almost a year later, when it was clear that the blockade would not achieve its original purpose of annexing the Western sector to Eastern Germany, the transit connection to Berlin was reopened on May 12, 1949, and traffic began to move back to the roads. The air bridge was officially closed on September 30 of the same year.