Fidel Castro and other Cuban dissidents invaded Cuba in 1956 and ousted the corrupt and oppressive dictator, Fulgencio Batista, and the Mafia (U.S.). It took the revolutionaries three years of guerrila warfare, but eventually Batista fled with the Cuban treasury (as usual with such dictatorships).
The U.S. Government took umbrage at Castro's revolution. We supported Batista because Batista guaranteed U.S. owned companies in Cuba, such as Coca Cola, various casinos, Diamond Sugar... Castro made no such guarantees. Batista's government and various other Cuban elite fledmostly to Miami. Castro nationalized the U.S. companies.
The wealthy and politically powerful Cuban exiles and the U.S. companies that lost properties, not to mention organized crime, pressured the U.S. Government into supporting invasion of Cuba by a task force of exiles. The CIA trained and supplied the Brigade 2506 but the invasion failed within hours of landing and the U.S. Government's plausible deniability was blown.
Khrushchev wrote President Kennedy that the USSR would "render the Cuban government all necessary help to repel an armed attack on Cuba". JFK backed off and never forgave the CIA for the botched and embarrassing covert action. The Miami exiles never forgave Kennedy and may have taken its revenge in Dallas.
Fidel is old and sick. The Miami exiles are excitedthe end is near. They're expecting to return to Cuba? To regain their estates and businesses? Do they really think the Cuban government depends on Fidel? Film at 11.