A number of factors are believed to of lead to the Cuban Missile Crisis in October 1962. Cuba used to be run by Batista, who was an American sympathiser and he allowed the US to have a navy base there. There were also a lot of US run and owned shops on Cuba. Then Fidel Castro lead a rebellion against Batista and won. Castro broke relations with the US and gave all the US run businesses to Cubans. The US encouraged Cuban exiles to rebel against Castro but after being beaten at the bay of Pigs they failed. Krushchev, the communist leader of the USSR (now Russia) armed Castro with nuclear weapons which were discovered by an American plane. President Kennedytried appeasing Krushchev, but after this failed he ordered a blockade of Cuba.
There was no clear cause. but many little events