The CIA began training the exiles in Costa Rica and other Central American countries under the administration of President Dwight D. Eisenhower, even before he broke off diplomatic relations with Cuba in January 1961. Eisenhower's successor, John F. Kennedy, approved the actual invasion.
The invasion started on April 15 when B-26 planes with Cuban markings bombed 4 airfields in Cuba. The media wires began to report that a military uprising had begun in Cuba, and that defecting pilots were bombing Cuban military installations and fleeing to Miami.
On April 17 1961 about 1,500 exiles armed with US weapons landed on the southern coast of Cuba at the Bay of Pigs. They hoped to find support from the local population, intending to cross the island to Havana, but it became quickly evident in the first hours of fighting that the exiles were not going to receive such support and were likely to lose. President Kennedy decided against giving the faltering invasion US air support (though 4 US pilots were allegedly killed or captured in Cuba during the invasion) as it was obvious that nothing short of US ground troops would save the operation and Kennedy was unwilling to commit to this. By the time fighting ended on April 19, ninety exiles were dead and the rest were captured.
The 1,189 captured exiles were tried and sentenced to 30 years in prison. After 20 months of negotiation with the United States, Cuba released the exiles in exchange for $53 million in food and medicine.
The failed Bay of Pigs invasion severely embarrassed the Kennedy administration, and made Castro wary of future US incursions into Cuba.
The CIA wrote a detailed internal report which lays blame for the failure squarely on internal incompetence.
The incident later featured as an example for the "groupthink" phenomenon. Groupthink says that a group of excellent thinkers is prone to radically wrong decision making because everyone in the group is so enthusiastic about being amongst powerful and knowledgeable men that they neglect to check basic assumptions, to push opposing views, or to consider that they may be just plain wrong. Among the grave errors committed in the Cuba crisis are:
Many military leaders almost certainly expected the invasion to fail but thought that this failure would force Kennedy to send in marines to save the CIA trained exiles. Kennedy, however, did not want a full scale war and abandoned the exiles.
The failed invasions led directly to the Cuban Missile Crisis two years later.