It only took half a century, but we finally have direct evidence of U.S. government leaders cryptically discussing ideas about assassinating Fidel Castro just months before the Cuban Missile Crisis.

Due to congressional investigations in the 1970s, we have long known of (unsuccessful) Central Intelligence Agency plots to kill Castro in the Eisenhower and Kennedy eras. And, based on what various CIA people later testified, it has also been believed that, strangely, John McCone, who headed the CIA for the last two years of the Kennedy presidency, did not want to discuss or even hear about assassination plots.

Earlier this year, I came across a document at the National Archives that seems to confirm this. But what I find most remarkable is that the document even exists. We have never seen any sort of documentation from the actual time of a high-level conversation about the taboo topic.

But there it was in State Department records from a late summer day in 1962: Secretary of State Dean Rusk had met at 11:30 a.m. with McCone, Bobby Kennedy (who told the CIA he wanted to attend), Defense Secretary Robert McNamara, and other advisers to JFK. The meeting was devoted to Castro’s Cuba, where intelligence showed the Russians pouring in men and military equipment. McCone’s notes of the meeting show participants agreeing that strong measures against Castro’s government were needed. But what kind? The notes show that participants couldn’t agree on that.

Only because Rusk’s secretary at the State Department was listening and taking notes when McCone called later that day, do we know much more about what came up in the meeting. Her notes show an upset CIA leader: “M[cCone] said the question came up this a.m. in connection with an individual that should notcome up in m[eetin]gs. M[cCone] does not think we should countenance talking or thinking about that.”

A little context is needed to make sense of the telephone call.

• First, the “individual” who was the overwhelming focus of the meeting was Castro.

•  Second, those meetings in the office and presence of the secretary of state were the policymaking elites of the Kennedy administration.

• Third, the Republican McCone was a tough Cold Warrior. That’s why JFK chose him as CIA head. McCone favored almost anything anyone proposed to deal with Castro, except murder. McCone was said to have been against anyone even raising the topic in his presence. “I could get excommunicated!” the Catholic McCone said.

The notes made as the telephone conversation unfolded show just that sort of abhorrence. In contrast, Secretary of State Rusk was less agitated over the topic, saying “he would not worry about it,” given the reliable people at the meeting. But the CIA director brushed off that assurance: He and Rusk could sit down and “talk privately,” presumably about the forbidden topic, but the “Sec[cretary] should take the posture of not countenancing it.” Without elaboration, the “Sec[retary] agreed.”

The words “Castro” and “assassination” are not there in the telephone conversation notes, but — given the morning meeting’s agenda and McCone’s notes of it — it is very hard to believe that the “individual” referred to in the subsequent phone call was anyone but Castro. The notes seem to be concrete evidence supporting stories from across the decades that McCone did not want others even to raise the idea in his presence of killing Castro.

Of course, the Central Intelligence Agency did try to kill Castro during the Kennedy era. How that could happen when the agency’s leader didn’t want the subject discussed in his presence has been the subject of many an author, but is still debated. I’m just amazed finally to see a contemporaneous record actually showing the forbidden topic being raised and then banished, at least for meetings with the CIA leader there.

And I’m struck by the irony: JFK, RFK, McCone, Rusk — they’re all long gone. Castro, the individual about whom those men obsessed, lives on.

David M. Barrett is a professor of political science at Villanova University and co-author, with Max Holland, of "Blind Over Cuba: The Photo Gap and the Missile Crisis," which is soon to be published.