The Jupiter missiles were an exceptionally vexing component of the U.S. nuclear arsenal. Because they sat aboveground, were immobile, and required a long time to prepare for launch, they were extremely vulnerable. Of no value as a deterrent, they appeared to be weapons meant for a disarming first strike—and thus greatly undermined deterrence, because they encouraged a preemptive Soviet strike against them. The Jupiters’ destabilizing effect was widely recognized among defense experts within and outside the U.S. government and even by congressional leaders. For instance, Senator Albert Gore Sr., an ally of the administration, told Secretary of State Dean Rusk that they were a “provocation” in a closed session of the Senate Foreign Relations Committee in February 1961 (more than a year and a half before the missile crisis), adding, “I wonder what our attitude would be” if the Soviets deployed nuclear-armed missiles to Cuba. Senator Claiborne Pell raised an identical argument in a memo passed on to Kennedy in May 1961.

Given America’s powerful nuclear superiority, as well as the deployment of the Jupiter missiles, Moscow suspected that Washington viewed a nuclear first strike as an attractive option. They were right to be suspicious. The archives reveal that in fact the Kennedy administration had strongly considered this option during the Berlin crisis in 1961.

It’s little wonder, then, that, as Stern asserts—drawing on a plethora of scholarship including, most convincingly, the historian Philip Nash’s elegant 1997 study, The Other Missiles of October—Kennedy’s deployment of the Jupiter missiles “was a key reason for Khrushchev’s decision to send nuclear missiles to Cuba.” Khrushchev reportedly made that decision in May 1962, declaring to a confidant that the Americans “have surrounded us with bases on all sides” and that missiles in Cuba would help to counter an “intolerable provocation.” Keeping the deployment secret in order to present the U.S. with a fait accompli, Khrushchev may very well have assumed America’s response would be similar to his reaction to the Jupiter missiles—rhetorical denouncement but no threat or action to thwart the deployment with a military attack, nuclear or otherwise. (In retirement, Khrushchev explained his reasoning to the American journalist Strobe Talbott: Americans “would learn just what it feels like to have enemy missiles pointing at you; we’d be doing nothing more than giving them a little of their own medicine.”)

Khrushchev was also motivated by his entirely justifiable belief that the Kennedy administration wanted to destroy the Castro regime. After all, the administration had launched an invasion of Cuba; had followed that with sabotage, paramilitary assaults, and assassination attempts—the largest clandestine operation in the history of the CIA—and had organized large-scale military exercises in the Caribbean clearly meant to rattle the Soviets and their Cuban client. Those actions, as Stern and other scholars have demonstrated, helped compel the Soviets to install the missiles so as to deter “covert or overt US attacks”—in much the same way that the United States had shielded its allies under a nuclear umbrella to deter Soviet subversion or aggression against them.

Remarkably, given the alarmed and confrontational posture that Washington adopted during the missile crisis, the tapes of the ExComm deliberations, which Stern has minutely assessed, reveal that Kennedy and his advisers understood the nuclear situation in much the same way Khrushchev did. On the first day of the crisis, October 16, when pondering Khrushchev’s motives for sending the missiles to Cuba, Kennedy made what must be one of the most staggeringly absentminded (or sarcastic) observations in the annals of American national-security policy: “Why does he put these in there, though? … It’s just as if we suddenly began to put a major number of MRBMs [medium-range ballistic missiles] in Turkey. Now that’d be goddamned dangerous, I would think.” McGeorge Bundy, the national security adviser, immediately pointed out: “Well we did it, Mr. President.”