During the CIA-orchestrated invasion of Cuba by anti-Castro exiles in April 1961, the president made a last-minute decision to keep U.S. bomber aircraft on the ground. Apparently, JFK was concerned that U.S. fingerprints on the operation might be too obvious [source: Lawrence].
With the lack of airpower, the coup failed, and many in the exile community blamed Kennedy. Even though he continued a clandestine CIA effort to eliminate Castro, it wasn't enough to satisfy the scores of armed militants who were eager to try another invasion. They grew even angrier after federal authorities shut down many of their training camps and confiscated weaponry in the spring of 1963.
In October, just seven weeks before JFK's killing, one anti-Castro militant warned, "We're going to give him the works when he gets in Dallas," according to a tape of the meeting in Dallas. In the wake of the assassination, an informant told the FBI that on the day before JFK was shot, another anti-Castro activist who was seeking to buy arms illegally boasted that his wealthy backers would put up the money "as soon as we take care of Kennedy" [source: HSCA].
Nevertheless, the Congressional probers who reopened the investigation of JFK's assassination concluded that the anti-Castro militants were more vociferous than menacing, and probably hadn't been involved [source: HSCA].