One of the most significant moments of the presidency of John F. Kennedy, who died 50 years ago today, began when the United States discovered Soviet nuclear missiles on Cuba. The Cuban missile crisis ended peacefully -- the Soviet Union withdrew the warheads in exchange for Kennedy pulling its own missiles from Turkey -- but came awfully close to sparking World War III, a threat that forever changed Americans' perceptions of the Cold War.

Historians have long debated how the crisis started, escalated and ended. One aspect of that debate getting a lot of attention on today's anniversary is Kennedy's role. Was it his fault that the world almost ended in nuclear annihilation in the fall of 1962? Here are the cases for, against, half-for-half-against and my own take.

The case that it was Kennedy's fault

The argument, explained nicely by colleague Dylan Matthews here, is that Kennedy provoked the Soviet Union into putting the missiles in Cuba and then overreacted when he found them. He had sponsored a failed militia invasion of Cuba with the Bay of Pigs debacle, leading Soviet Premier Nikita Khrushchev to fear a fuller U.S. invasion. Kennedy had also put medium-range nuclear weapons in Turkey -- so-called "first-strike weapons" because they were close enough to Moscow to be used to start a war.

Khrushchev, in this view, placed the missiles in Cuba only in response to Kennedy's provocations. The Soviet leader felt compelled to re-balance the playing field with his own potential first-strike weapons; he also wanted to prevent an American invasion of Cuba. Kennedy, Matthews argues, should have understood this and seen the warheads as a reasonable and defensive reaction rather than a provocative step toward war. But Kennedy took it as an implicit act of aggression and responded with the threat of severe escalation, which is how the world almost ended.

The case that it wasn't Kennedy's fault

Everyone pretty much concedes that the Bay of Pigs was a catastrophe. But it also virtually guaranteed that the United States, badly embarrassed by the incident, would not attempt a similar stunt again, much less the full military invasion that Khrushchev feared. His miscalculation led him to install the nuclear weapons on Cuba -- so did his mistaken belief that Americans would shrug off the warheads as a tit-for-tat response to the U.S. missiles in Turkey. Americans, Kennedy included, actually found it pretty terrifying. The fact that Khrushchev had installed them in total secret deepened fears that these weapons were meant not to protect Havana, but to launch a surprise first-strike against Washington.

In this view, the mere chance that the Soviet Union would or could use the Cuba-based missiles to initiate a nuclear war against the United States made them unacceptable. Kennedy responded by publicly raising the pressure with an embargo against Cuba but also quietly offering Moscow concessions should it back down; historian Graham Allison argues that this increased the immediate risk of war but also created the opportunity for the ultimate, peaceful resolution.

The case that it was and wasn't Kennedy's fault

Both Kennedy and Khrushchev profoundly misunderstood one another's goals and intentions, leading the United States and the Soviet Union to misread the situation and almost walk into a war neither of them wanted. As I wrote last year on the crisis's 50th anniversary, each leader failed to understand the degree to which his counterpart simply saw a different world.

At the time, Kennedy and Washington in general were obsessed with the perceived "missile gap" with the Soviet Union, an arms race they saw as all-important. They worried that, should any one side get too far ahead of the other, that "winning" side would be tempted to use its advantage to start and "win" a nuclear war before the other could catch up. So, when Khrushchev put missiles in Cuba, they assumed he was attempting to leap ahead of the United States in the placement of strategic nuclear weapons -- a possible prelude to war.

Kennedy was wrong, but Khrushchev was making a similar mistake. He saw the Cold War as driven not primarily by the arms race, an American obsession, but by a grand ideological struggle. Western capitalist imperialism, he believed, sought ever-outward expansion. Kennedy would try again for Cuba before pushing on to the rest of Latin America. American aggression could be deterred only with defensive nuclear weapons. Without U.S. meddling, Khrushchev believed, Soviet-style communism would flow naturally from Cuba to the rest of the region.

They were both very wrong, not just about the forces driving the world but about one another's motivations. Each assumed that the other must naturally share his assumptions and his understanding of the world. Which brings me to...

The case that it was the Cold War's fault

The Cold War had many, many causes, but this mutual misunderstanding was certainly one of them, and not just during the Cuban missile crisis or even Kennedy's tenure. American and Soviet leaders had been misreading one another's intentions, overstating one another's strengths and playing down  one another's weaknesses for years before Kennedy took office and would continue to do so for decades after. Those mistakes consistently led both countries to escalate both defensively and offensively and to shape their foreign policies around one another.

Ironically, it was Ronald Reagan, the American president we most remember as an anti-Soviet hard-liner, who along with Soviet leader Mikhail Gorbachev would finally break down those mental barriers and attempt to erase the nuclear threat once and for all. Right up until the collapse of the Berlin Wall, much of the White House -- including future CIA director and defense secretary Robert M. Gates -- opposed those talks, warning that Gorbachev was a wolf in sheep's clothing. They were wrong, just as Kennedy had been wrong about Khrushchev's intentions during the Cuban missile crisis and just as Khrushchev had been wrong about Kennedy's intentions toward Cuba. But that was the Cold War -- completely insane.