The Soviet Union was so afraid of being invaded because the US had nuclear weapons that the USSR did not have at the time, and they considered they were at a clear disadvantage.
So the Russians committed to work hard at developing his nuclear weapons. The Soviet Union detonated its first nuclear bomb on August 29, 1949. This created an important impact on the world scene because now the Soviets could represent a threat to the United States. The Cold Years and the arms race had begun.
The other options of the question were A) They were a small country with a weak military. B) Every country in the world was their enemy. C) The country had been invaded multiple times in their recent history.
