Why did President Kennedy take action against Soviet bases in Cuba in 1962?

President John F. Kennedy took action against Soviet bases in Cuba in 1962 because the Soviets had secretly placed nuclear missiles on that island.  Kennedy felt that the US could not tolerate the presence of these missiles and so he felt that he had to take action when he found out about them.  This episode is known as the Cuban Missile Crisis.

In 1962, the United States was able to hit the most important parts of the Soviet Union with nuclear missiles while the Soviets were not able to hit any part of the US except for Alaska.  This was because the US had allies in Europe, not far from Russia, where they could site nuclear weapons while the Soviets had not had any such allies near to the lower 48 states of the US until Cuba became communist in 1959.  Therefore, the Soviets felt that they were at a great disadvantage.  They tried to make up for this in 1962 by placing missiles in Cuba.

When Kennedy found out about the missiles (from pictures taken by spy planes flying over Cuba), he felt that the US could not allow them.  He felt that nuclear weapons in Cuba that could hit the US constituted a grave danger to the US, one that he could not accept.  (In other words, he and his advisors felt it was acceptable for the US to be able to attack the Soviets, but not for the Soviets to be able to attack the US.)  Because of this, he ordered a naval blockade of ships coming to Cuba so they could be inspected to be sure they were not carrying more missiles or other things needed for the missile bases. This was a dangerous move, but luckily the Soviets were willing to back down and remove the missiles in exchange for a public promise by the US not to invade Cuba and a secret agreement that the US would remove its own nuclear weapons from Turkey.  This was the only action that Kennedy actually took against the bases.  He did not attack them directly or anything like that as he did not want to start a war.  The Cuban Missile Crisis is seen as one of the most dangerous incidents in the Cold War since it could have led to a war between the US and the USSR.