Final answer:
The main reason the Soviets placed missiles in Cuba was to deter another American-supported invasion and protect their ally, as well as to balance the military situation against the US.
Step-by-step explanation:
Main Reason for Placement of Soviet Missiles in Cuba
The main reason for the Soviet Union placing missiles in Cuba was to deter another American-supported invasion of the island. This strategy was part of a defensive move to protect their ally, Cuba, under Fidel Castro, from further US attempts to overthrow the communist government, as exemplified by the Bay of Pigs invasion.
The Soviet Union, led by Nikita Khrushchev, sought to bolster Cuba's defenses and enhance their geopolitical influence in the Western Hemisphere. In doing so, the USSR would send a message to the US and other countries in Latin America that the Soviets were capable of protecting their allies against American aggression. This was also a strategic move to counteract the presence of US missiles in Turkey and to prevent Cuba from becoming vulnerable to future US military actions.
By placing nuclear missiles in Cuba, the Soviet Union also created a deterrent that balanced the military scales, with Soviet nuclear capabilities now within striking distance of the United States. The presence of Soviet missiles in Cuba was a direct challenge to US policy and marked a significant escalation in the Cold War, leading to the Cuban Missile Crisis. However, Khrushchev’s actions were primarily aimed at safeguarding the Soviet Union's ally rather than initiating an unprovoked attack on South America or the United States itself.