In April 1961... the Soviet Union were worried that the United States of America would invade communist ruled Cuba and overthrow the Cuban President Fidel Castro.... Nikita Khrushchev, the leader of Soviet Union, decided to convert Cuba into a Russian base. In 1962, placed nuclear missiles... Three weeks after the Soviet Union had placed the nuclear weapons in Cuba, the Americans became aware of it. They became reluctant to do anything that might lead to full scale war between the two countries... A clash seemed imminent in what came to be known as "Cuban Missile Crisis". The prospects of this clash made the whole world nervous.
Why was the Soviet Union worried about America invading Cuba?

Explanation

The Soviet Union was worried about America invading Cuba that the US would overthrew Cuban President Fidel Castro to capture power in Cuba.