Question

Which Soviet action during the early years of the Cold War almost led to a direct war between it and the United States?
A. The Soviets made a secret treaty with Hitler
B. Soviet spies stole America’s atomic secrets.
C. The Soviets blockaded Berlin.
D. Communists seized control of China.

Answer 1

I'd go with (C). It was one of the earliest incidents of the Cold War.

Berlin was in East Germany (held by the Soviets) but under treaty, the city was also divided into East and West. The Soviets decided to close the land route through East Germany to West Berlin in order to make them the only source of food, water, etc.. to that side of the city giving them indirect control over it. They were within their rights to do so -- the agreement between the Soviets and the West didn't really flesh out road and rail rights leaving it vague enough for the Soviets to take advantage of.

The Allies, on the other hand, organized an effective airlift that supplied the city by air and since the Soviets didn't want to shoot down US and allied planes, had no choice but to let them land and feed West Berlin. Eventually, the blockade was lifted after seeing how ineffective it was in intimidating West Berlin or their allied friends.