At the time President Kennedy was gunned down, the CIA could not possibly have been unfamiliar with the alleged assassin, ex-Marine Lee Harvey Oswald. Unless it was comatose, Oswald must have been a person of interest to the Agency long before the assassination. In 1957–58, Oswald had been stationed as a radar operator at the Atsugi Naval Air Base in Japan, where there was a major CIA station and from which the Agency’s U2 spy planes flew high-altitude missions over the Soviet Union; in 1959, the CIA knew, Oswald had defected to the Soviet Union, announced he had secrets to turn over to the Soviets, and attempted to renounce his American citizenship. In late September/early October 1963, six weeks before JFK’s murder, Oswald had been under CIA surveillance when he visited Soviet and Cuban diplomatic facilities in Mexico City multiple times, supposedly to arrange a return to the Soviet Union (or to visit Cuba, or both).
For years, critics have accused the CIA of suppressing information relevant to the assassination of President Kennedy. The Agency, they allege, even withheld pertinent information from both the Warren Commission (which investigated the assassination in 1963–64) and the U.S. House of Representatives Assassinations Committee (which reinvestigated the assassination in 1976–79).
These critics, we now know, were right.
Wilkes, Donald E. Jr., "The CIA and the JFK Assassination, Pt. 1" (2015). Popular Media. 235.