On Oct. 22, 1962, Kennedy asked Eisenhower whether he thought Soviet leader Nikita Khrushchev would start a nuclear war if the United States invaded Cuba to take out the missiles.
"Oh, I don't believe that they will," Eisenhower said. "Something may make these people shoot them off. I just don't believe this will."
When the crisis abated without either side having to fire a shot, Kennedy placed calls to all three living former presidents -- Herbert Hoover, Harry Truman and Eisenhower -- to give them relieved updates. Eisenhower warned Kennedy to stay vigilant, again referring to the Soviets as "these people."
"They take any spot in the world. They don't care where it is," he said.
"That's right," Kennedy agreed.
On civil rights, the tapes show a president being pulled into deeper and more decisive action by events far from the Oval Office. He pushes Southern governors to respect federal power, while at the same time counseling African-American leaders for patience in understanding the limits of his authority in forcing cities and states to end segregation and advance voting rights.
In May 1963, on the day The New York Times ran a photograph with police dogs attacking peaceful protesters, Kennedy told leaders of Americans for Democratic Action that even a president can't stop some injustices.
"There is no federal law that we can pass to do anything about that picture in today's Times. Well there isn't," he said. "I mean, what law can you pass to do anything about police power in the community of Birmingham? There is nothing we can do. There is no federal law, is no federal statue, no federal law we can pass."
But Kennedy would be persuaded by a string of violent clashes that more federal intervention was necessary. Civil rights leader A. Philip Randolph told the president to his face that he needs to "lead this crusade" to overcome congressional opposition to a civil rights law, and Kennedy seemed to agree, mapping out the start of a legislative strategy.
The Rev. Martin Luther King Jr. made a personal, emotional appeal to Kennedy in September 1963:
"The Negro community is about to reach a breaking point," King told Kennedy on the tapes. "There is a great deal of frustration and despair and confusion in the Negro community, and there is a feeling of being alone and not being protected. If you walk the street, you aren't safe. If you stay at home, you are not safe, there is a danger of a bomb. If you're in church now, it isn't safe."
Kennedy took on the cause of civil rights even though he knew it "could have cost him the election" in 1964, Caroline Kennedy recalled.
"So it was a very courageous thing to do. And I think it shows," she said. "It shows, also, the kind of behind-the-scenes cooperation with Martin Luther King and the leaders of the movement and then the great sort of relief when they come in after the March on Washington and that's been such an incredible event and such a success. And so everybody is so proud."