Throughout the spring and summer of 1963, the leaders of the United States and Israel – President John F. Kennedy and Prime Ministers David Ben-Gurion and Levi Eshkol – were engaged in a high-stakes battle of wills over Israel’s nuclear program. The tensions were invisible to the publics of both countries, and only a few senior officials, on both sides of the ocean, were aware of the severity of the situation

In Israel, those in the know saw the situation as a real crisis, as a former high-level science adviser, Prof. Yuval Ne’eman, told one of us (Avner Cohen) 25 years ago. Ne’eman recalled that Eshkol, Ben-Gurion’s successor, and his associates saw Kennedy as presenting Israel with a real ultimatum. There was even one senior Israeli official, Ne’eman told me, the former Israel Air Force commander Maj. Gen. (res.) Dan Tolkowsky, who seriously entertained the fear that Kennedy might send U.S. airborne troops to Dimona, the home of Israel’s nuclear complex.

What was at stake was the future of Israel’s nuclear program. Kennedy, with an exceptionally strong commitment to nuclear nonproliferation, was determined to do all he could to prevent Israel from producing nuclear weapons. Ben-Gurion (and later Eshkol) were equally determined to complete the Dimona project. For them, nuclear capability was an indispensable insurance policy against existential threats to Israel. The exchange between the American president and the two prime ministers illustrates both Kennedy’s tenacity and the Israeli leaders’ recalcitrance.

Earlier this week, we published – on the website of the National Security Archive – a collection of nearly 50 American documents from U.S. archives that illuminate for the first time the full scope of this secret American-Israeli confrontation. The collection includes not only the entire exchange of messages between the leaders – Kennedy, Ben-Gurion and Eshkol – but also many related American documents, some of which were declassified and became available only in recent months.

These include a full report of the U.S. inspectors who visited Dimona in 1964; memos in which senior White House officials deliberated how to deal with the prime minister; and intelligence assessments that had analyzed whether Israel’s nuclear reactor was, as the Israelis insisted, really meant for peaceful use.

One senior Israeli official feared Kennedy might send U.S. airborne troops to Dimona, the home of Israel’s nuclear complex.

Kennedy, Nonproliferation and Israel

More than any other country, it was his dealings with Israel that impressed upon President Kennedy both the complexity and the difficulty of halting nuclear proliferation.

In the fall of 1960, not long after Kennedy’s election, the outgoing Eisenhower administration first became aware of the Dimona reactor that Israel and France had begun building in secret during 1958. The CIA issued a Special National Intelligence Estimate (SNIE) that determined that “plutonium production for weapons is at least one major purpose of this effort.” Furthermore, the estimate predicted that if the Arab world believed that Israel was acquiring a nuclear-weapons capability, it would cause “consternation,” and blame would be directed toward the U.S. and France for their presumed support of the project.

At a White House briefing on January 19, 1961, the eve of his inauguration, Kennedy inquired which countries were seeking the bomb. “Israel and India,” outgoing Secretary of State Christian Herter told him, adding that the then-newly discovered Dimona reactor would be able to produce 90 kilograms of weapons-grade plutonium by 1963, enough for 10 to 15 nuclear weapons. Herter urged Kennedy to press hard for inspections of Dimona before Israel introduced such weapons into the Middle East.

Although Kennedy had a variety of tough issues to address from the outset – ranging from the CIA’s plans for an invasion of Cuba to a crisis over Laos – within days of taking office he began urging Ben-Gurion to accept a U.S. visit to Dimona, insisting that a visit was a condition for good diplomatic relations. In responding, Ben-Gurion dragged his feet, citing a cabinet crisis that had to be resolved.

By April 1961 – by which time Ben-Gurion, who had resigned as prime minister on January 31, in protest of his colleagues’ conduct regarding the Lavon affair, was heading a caretaker government – Israeli Ambassador to Washington Avraham Harman told the administration that Israel had agreed to a tour of Dimona by U.S. officials. On May 20, two Atomic Energy Commission scientists, U. M. Staebler and J. W. Croach, Jr., visited the site. Its management team explained that the technological rationale for the project was to gain experience in building and operating nuclear reactors that could be used in the future for peaceful power generation.

From U.S. documents, we know that the AEC team was “satisfied that nothing was concealed from them and that the reactor is of the scope and peaceful character previously described.” This visit laid the foundations for a meeting between Ben-Gurion and Kennedy in New York, on May 31, 1961.

The rationale Ben-Gurion presented to Kennedy during that meeting, held at the Waldorf Astoria Hotel, was consistent with what the Dimona management team had told the American scientists: The nuclear project was peaceful in nature; it was about energy and development. However, the Israeli leader's narrative also left a little wiggle room for a future reversal. His caveat amounted to a few words: “for the time being, the only purposes are for peace. … But we will see what will happen in the Middle East. It does not depend on us” (italics added).

Open gallery view Kennedy and Ben-Gurion. Their meeting in May 1961 helped to clear the air but did not remove lingering American doubts and suspicions about Israel’s nuclear intentions. Credit: DPA / AFP

The ‘spontaneous’ second visit

The meeting with Ben-Gurion helped to clear the air for some time, but it did not remove lingering American doubts and suspicions about Israel’s nuclear intentions. Starting in June 1962, the Americans began trying to arrange a second visit to Dimona, but failed to make headway. It wasn’t until September 26, 1962, after frequent requests over several months, that such a visit finally took place.

Until recently, little was known from American documents about that second Dimona visit except that U.S. Ambassador to Israel Walworth Barbour referred to it as “unduly restricted to no more than 45 minutes.” Recently declassified documents shed new light on the visit. The key document is a memo, written on December 27, 1962, by the deputy director of the Bureau of Near Eastern Affairs, Rodger Davies, to Assistant Secretary Philip Talbot, detailing the story of the second visit.

After the two AEC visiting scientists – Thomas Haycock and Ulysses Staebler – had inspected the small, U.S.-supplied reactor at Nahal Sorek, they were unexpectedly offered a sightseeing tour at the Dead Sea. Later, as they were being driven back to their hotel, their host told them that they were near the Dimona reactor and that a meeting with the director could be arranged. The director was not there, but they met and were briefed by the principal engineer, who gave them a 40-minute tour of the facility. The report’s final sentence states that “the inspectors were not certain whether they were guests of their scientist-hosts or on an inspection. Although they have not had time to see the entire installation, and although there were some buildings they did not enter, they were able to confirm the research nature of the installation.”

Within days of taking office, Kennedy began urging Ben-Gurion to accept a U.S. visit to Dimona, insisting it was a condition for good ties.

The highly unconventional nature of the visit stirred suspicion in Washington, especially in the intelligence community. During one interagency meeting, a senior intelligence expert, probably Deputy Director of Intelligence Ray Cline, was quoted as saying that “the immediate objectives of the visit may have been satisfied, [but] certain basic intelligence requirements were not.” It was also observed that “there were certain inconsistencies between the first and second inspection reports.”

Whatever the doubts about the ultimate intelligence value gleaned from the second visit, the State Department passed on its conclusions to other countries. A few weeks after the second visit, just as the Cuban Missile Crisis of October 1962 was unfolding, the State Department began to quietly inform selected governments that Dimona was a peaceful nuclear project.

Early 1963: Renewed U.S. interest

In early 1963, however, concerns over Dimona resurfaced. By late January, Kennedy had received a new National Intelligence Estimate, entitled “The Arab-Israeli Problem,” that highlighted the weapons potential of the Dimona reactor. On Israel’s nuclear potential, the NIE concluded that the facility would become operational later that year and that by the following year, 1964, “if operated at its maximum capacity for the production of weapon-grade plutonium, the reactor could produce sufficient plutonium for one or two weapons a year.”

To produce plutonium, Israel would need a facility to separate it from spent reactor fuel, and the NIE acknowledged that at the time U.S. intelligence had “no evidence to confirm or deny the existence of a separation facility.” The NIE noted that the Israelis had made contradictory statements about a reprocessing plant, including statements in 1961 (during the Ben-Gurion-Kennedy meeting) that they planned to build a pilot one, and in 1962 (apparently during the second Dimona visit) that they had no such plans. As our collection indicates, the Israelis told the U.S. inspectors in January 1964 that they had delayed constructing a pilot plant for reprocessing.

Reacting to the intelligence estimate, NSC official Robert Komer suggested that Israel “will attempt to produce a weapon sometime in the next several years and could have a very limited capability by 67-68.” In retrospect, and based on earlier publications on this subject, we can say that that assessment turned out to be on target. Komer informed the president that “we are planning a better look [at Dimona] in the next month or so.”

Open gallery view The reactor at Nahal Sorek. After two visiting Atomic Energy Commission scientists had inspected this small, U.S.-supplied facility, they were unexpectedly offered a sightseeing tour – that ended with a stop at Dimona. Credit: Alon Ron

By early February, American officials were characterizing the second visit to Dimona as a “fiasco” and urged fresh thinking within the AEC, State Department, and probably the White House about how the United States could effectively and systematically monitor the reactor. One conclusion was that an effective inspection regime would demand biannual visits. The reason for the proposed frequency was purely technical: To trace extraction of weapons-grade plutonium, there must be two visits annually, because production reactors operate on a much shorter schedule than research reactors.

Weeks later, in early March, Kent Sherman, director of the Office of National Estimates, which prepared the NIEs, signed an intelligence estimate detailing the grave consequences of Israeli nuclearization. “Israel’s policy toward its neighbors would become more rather than less tough… it would … seek to exploit the psychological advantages of its nuclear capability to intimidate the Arabs and to prevent them from making trouble on the frontiers.” Furthermore, in dealing with the United States, Israel “would use all means in its command to persuade [it] to acquiesce in and even to support, its possession of nuclear capability.”

On March 25, 1963, President Kennedy and CIA Director John A. McCone discussed the Israeli nuclear program. According to McCone, Kennedy raised the “question of Israel acquiring nuclear capability,” and McCone provided Kennedy with Kent’s estimate of the anticipated negative consequences of Israeli nuclearization. According to McCone, Kennedy then instructed National Security Adviser McGeorge Bundy to guide Secretary of State Dean Rusk, in collaboration with the CIA director and the AEC chairman, to submit a proposal “as to how some form of international or bilateral U.S. safeguards could be instituted to protect against the contingency mentioned.” That also meant that the “next informal inspection of the Israeli reactor complex [must] …be undertaken promptly and... be as thorough as possible.”

Within days, this presidential request was translated into diplomatic action. On April 2, Ambassador Barbour met Prime Minister Ben-Gurion and presented the American request for his “assent to semi-annual visits to Dimona [among themselves American referred to them as ‘inspection visits’] perhaps in May and November, with full access to all parts and instruments in the facility, by qualified U.S. scientists.” Ben-Gurion, apparently taken by surprise, responded by saying the issue would have to be postponed until after Passover, which that year ended on April 15. To highlight the point further, two days later, Assistant Secretary Talbot summoned Israeli Ambassador Harman to the State Department and presented him with a diplomatic démarche on the inspections. This message to Ben-Gurion was the first salvo in what would become the toughest American-Israeli confrontation over the Israeli nuclear program.

The Kennedy-Ben-Gurion exchange

Kennedy threatened that failure to present 'reliable information' on Dimona would 'seriously jeopardize' Washington’s 'commitment to and support of Israel.'

Ben-Gurion was expected to respond to the U.S. request on Dimona at his next meeting with Ambassador Barbour, following Passover. The Israeli premier was not ready – politically or psychologically – to confront a determined U.S. president. Nor, however, could he accept semi-annual visits, which would have been a death blow to Dimona. In a sense, Ben-Gurion found himself trapped by his original “peaceful purpose” pledge that aimed at preventing a confrontation with the United States.

Ben-Gurion decided to try to avoid confrontation and evade the nuclear issue by attempting to persuade Kennedy to think about Israel’s overall security predicament. The prime minister needed to change the subject of the conversation from Kennedy’s specific demand for American twice-a-year visits to Dimona into a broader and urgent discussion about Israel’s overall strategic situation. But how could he do that? How could he evade Kennedy’s demand?

Ben-Gurion soon had an opportunity to change the subject. On April 17, 1963, Egypt, Syria and Iraq signed the Arab Federation Proclamation, calling for a military union to bring about “the liberation of Palestine.” Such rhetoric was not new at the time and it is not clear whether Ben-Gurion genuinely saw the proclamation as an existential threat to Israel. Nevertheless, it gave him a golden opportunity to argue that Israel was facing just that, and hence – by tacit implication – that Israel was justified in its efforts to generate an “insurance policy.”

On April 26, more than three weeks after the original U.S. demand concerning Dimona, Ben-Gurion responded to Kennedy with a seven-page letter that focused on broad issues of Israeli security and regional stability. Claiming that Israel faced an unprecedented threat, Ben-Gurion invoked the specter of “another Holocaust,” and insisted that Israel’s security should be protected by joint external security guarantees, to be extended by the U.S. and the Soviet Union. Why did Ben-Gurion make this fantastic and unrealistic proposal at this time? He was probably trying to provide the U.S. with a tacit rationale for the real purpose of Dimona, without explicitly stating it and without directly countering or rejecting Kennedy’s demands.

Kennedy, however, was determined not to let Ben-Gurion change the subject. On May 4, he replied to the prime minister, assuring him that while “we are watching closely current developments in the Arab world,” the Israeli leader’s alarm over the Arab Federation Proclamation was overstated. As to Ben-Gurion’s proposal for a joint superpower declaration, Kennedy dismissed both its practicality and its political wisdom. Kennedy was much less worried about an “early Arab attack” than he was by “a successful development of advanced offensive systems which, as you say, could not be dealt with by presently available means.”

Open gallery view The Dimona reactor.

In tandem with the letter, Ambassador Barbour met with Ben-Gurion to further clarify the American request for semi-annual visits to Dimona. Although records of this meeting remain classified, Kennedy and his advisers suspected that Ben-Gurion was initiating a process of bargaining over the Dimona visits – that is, by linking the visits to other possible Israeli goals, such as obtaining a security guarantee. Barbour was instructed to remind the Israeli leader that he and other senior officials had already approved inspections unconditionally.

Kennedy’s dismissive reply did not deter Ben-Gurion. In another lengthy and highly emotional reply to Kennedy’s May 4 letter, Ben-Gurion continued his earlier effort to change the conversation while also indirectly explaining the true purpose of Dimona. When senior Foreign Ministry official Gideon Rafael saw the draft, he advised against sending it, arguing that the letter “looks sick” (holani, in the original Hebrew), and that “the prime minister must not speak about something that seems sick.” Ben-Gurion usually rejected editorial advice and, true to form, he insisted on maintaining both its tone and length.

On the surface, the letter seems to ignore Dimona entirely, as if the prime minister had either overlooked or entirely dismissed Kennedy’s letter and the recent U.S. requests for visits. Instead, in a tone of an old statesman who had seen it all, Ben-Gurion wrote of his impressions of Egyptian president Gamal Abdel Nasser and his pan-Arabism, drawing an analogy between the Egyptian, together with other contemporary Arab leaders, and Hitler: “Knowing them I am convinced that they are capable of following the Nazi example. Nasser is in fact adopting the National-Socialist ideology of the Nazis. For many years the civilized world did not take seriously Hitler’s statement that one of his aims was the worldwide extermination of the Jewish people. I have no doubt that a similar thing might happen to Jews in Israel if Nasser succeeded in defeating our army.”

Acknowledging Kennedy’s view that a joint U.S.-Soviet security guarantee was politically impossible, Ben-Gurion now suggested a sweeping, bilateral U.S-Israel security agreement that would include the following: a supply of U.S. arms equivalent to what the Arabs were receiving from the Soviet Union, the transformation of Jordan’s West Bank into a demilitarized zone, and “a plan of general disarmament between Israel and the Arab states under a system of mutual and international inspection and control.”

This was a laundry list of unrealistic ideas and proposals. Again, Ben-Gurion may have meant to convey to Kennedy his rationale for the Dimona project, while avoiding expressing it explicitly. By reminding Kennedy that another Holocaust was possible and suggesting (indirectly) that Israel could not feasibly obtain a credible external security guarantee, he was effectively signaling to the president why Israel wanted a nuclear deterrent in the first place.

Ben-Gurion wasn't ready – politically or psychologically – to confront a determined Kennedy. Nor could he accept semi-annual visits, which would have been a death blow to Dimona.

In his monumental new biography of Israel’s first prime minister, “Ben-Gurion: A State at Any Cost,” due out in English this summer, Israeli historian Tom Segev reads this letter as if Ben-Gurion was actually considering giving up Dimona in return for some sort of security guarantee. We do not believe that Ben-Gurion ever seriously entertained giving up the nuclear project. Yes, Ben-Gurion was pushing for security guarantees, but realistically he must have known that goal was not in the cards, so long as Israel neighbors did not recognize her. From Kennedy’s perspective, providing Israel with security guarantees would have been a clear sign of favoritism toward, and would have undermined U.S. relations with the Arab states.

Kennedy, however, would not budge on Dimona, and the disagreements became a “pain in the neck” for him, as Robert Komer later wrote. The confrontation with Israel escalated when the State Department transmitted Kennedy’s latest letter to the Tel Aviv embassy on June 15 for immediate delivery to Ben-Gurion by Ambassador Barbour. In the letter Kennedy fleshed out his insistence on biannual visits with a set of detailed technical conditions. The letter was akin to an ultimatum: If the U.S. government could not obtain “reliable information” on the state of the Dimona project, Washington’s “commitment to and support of Israel” could be “seriously jeopardized.”

But the letter was never presented to Ben-Gurion. The telegram with Kennedy’s letter arrived in Tel Aviv on Saturday, June 15, the day before Ben-Gurion’s announcement of his resignation, a decision that stunned his country and the world. Ben-Gurion never explained, in writing or orally, what led him to resign, beyond citing “personal reasons.” He denied that his move was related to any specific policy issues, but the question of the extent to which Kennedy’s Dimona pressure played a role remains open to speculation to the present day.

Eshkol’s first crisis

On July 5, less than 10 days after Levi Eshkol succeeded Ben-Gurion as prime minister, Ambassador Barbour delivered to him a first letter from President Kennedy addressing him as Israel’s new leader. The letter was virtually a copy of the undelivered letter of June 15 to Ben-Gurion, with just a few congratulatory lines added at the top. Not since President Dwight Eisenhower’s message to Ben-Gurion, during the Suez crisis in November 1956, demanding an immediate Israeli withdrawal from the peninsula, had an American president been so direct in his demand with an Israeli prime minister. As Yuval Ne’eman witnessed it, it was immediately apparent to Eshkol and his advisers that Kennedy’s demands were akin to an ultimatum, and thus constituted a crisis in the making.

A stunned Eshkol, in his first and interim response, on July 17, requested more time to study the subject and for consultations. Eshkol confided to Ambassador Barbour his “surprise” over Kennedy’s statement that the U.S. commitment to and support of Israel could be “seriously jeopardized.” The premier noted that while he hoped that U.S-Israeli friendship would grow under his watch, “Israel would do what it had to do for its national security and to safeguard its sovereign rights.” Barbour, apparently wanting to mitigate the bluntness of the letter, assured Eshkol that Kennedy’s statement was “factual”: Critics of strong U.S.-Israel relations might complicate the diplomatic relationship if Dimona was left uninspected.

Later in the discussion, we learn from the newly declassified documents, Eshkol asked a blunt question that Ben-Gurion had never dared to ask: How would Washington react to an Israeli proposal to “consult in advance” with the United States, “in the event that, sometime in the distant future,” Middle Eastern developments made it necessary to “embark on a nuclear weapons program?” Barbour, of course, was not authorized to answer such a hypothetical question, so he restated the U.S. view that the “introduction” of nuclear weapons into the Middle East would be “especially grave.” No doubt, Barbour understood the significance of Eshkol’s question: He was hinting, openly but tentatively, that there were conceivable circumstances under which Israel might “embark on a nuclear weapons program.”

Open gallery view President Johnson greets Levi Eshkol, 1968. The president never pressed the Israeli leader hard for biannual U.S. visits to Dimona, the way Kennedy did with Ben-Gurion. Credit: Lynn Pelham/The LIFE Picture Collection/Getty Images

On August 19, after six weeks of consultations that generated at least eight different drafts, Eshkol handed Barbour his written reply to Kennedy’s demands. It began by reiterating Ben-Gurion’s past assurances that Dimona’s purpose was peaceful. As to Kennedy’s request, Eshkol wrote that given the special relationship between the two countries, he had decided to allow regular visits of U.S. representatives to the Dimona site. On the specific issue of the schedule, Eshkol suggested – as Ben-Gurion had in his last letter to Kennedy – that late 1963 would be the time for the first visit: By then, he wrote, “the French group will have handed the reactor over to us and it will be undertaking general tests and measurements of its physical parameters at zero power.”

Eshkol was explicit that the first American visit should be held before the start-up stage, but was vague on the proposed frequency of visits. Eshkol disregarded Kennedy’s demand for biannual tours, while avoiding a frontal challenge to Kennedy’s request. “Having considered this request, I believe we shall be able to reach agreement on the future schedule of visits,” Eshkol wrote. In sum, the prime minister split the difference: To end the confrontation, he assented to “regular visits” by U.S. scientists, but he did not accept the idea of the prompt visit that Kennedy wanted and avoided making an explicit commitment to biannual inspections. Kennedy’s appreciative reply did not mention these divergences, but assumed a basic agreement on “regular visits.”

The ambiguities of Eshkol’s reply were understood in Washington, but played down. In a detailed memo that the acting secretary of state, George Ball, wrote to Kennedy, the overall assessment was positive: Eshkol’s reply, “although not entirely what we wanted, probably represents the most we can hope.” Eshkol’s vagueness about Kennedy’s most important demand, twice-yearly visits to Dimona, was well recognized, but “we prefer to give him [Eshkol] the benefit of the doubt, relying on our interpretation, the prime minister’s oral statement that future agreement ‘will give no trouble.’” It turned out that Kennedy’s insistence of biannual visits was never accepted, although it remained on the U.S. agenda.

In the wake of Eshkol’s letter, the first of the long-sought regular inspection visits to Dimona took place in mid-January 1964, two months after Kennedy’s assassination. The Israelis told the American visitors that the reactor had gone critical only a few weeks earlier, but that claim was not accurate. Israel acknowledged years later that the Dimona reactor became operational in mid-1963, as the Kennedy administration had originally assumed.

Both the U.S. and the Israelis kept the visit secret, with leaks to the press effectively contained for over a year. The inspection took place over the course of a single day instead of the two days sought by the inspectors. The shorter time line meant that some buildings and parts of buildings were not seen, although the inspectors reported that the visit was “as comprehensive and thorough as the time permitted.” Their findings raised no suspicions of weapons-related activities, but it was “the impression of the team that the Dimona site and the equipment located there represented an ambitious project for a country of Israel’s capabilities.”

The issue of Israel’s possible reprocessing of spent fuel for plutonium continued to bedevil U.S. intelligence throughout the 1960s. No one was sure whether Israel already had a secret reprocessing site or had yet to build one.

Looking back

In retrospect, however, the 1963 exchange of letters between Kennedy and Ben-Gurion and Eshkol was the climax of the battle the U.S. leader waged against the Israeli nuclear project throughout his presidency. For Kennedy, the stakes were higher than the status of Israel’s nuclear program. At issue was the fate of his effort to halt global nuclear proliferation. Israel was the first such case the Kennedy administration had to face in which it had some political leverage. If Kennedy failed to halt Israel’s nuclear aspirations, how could he stop others, such as India?

For Ben-Gurion, Dimona was the most precious project he was involved in during his last decade in office. The establishment of the Negev Nuclear Research Center was the result of the prime minister’s deepest anxieties about Israel’s future, the fears of an old man that he attempted to share with Kennedy in his letter of late April 1963. The Dimona project was probably also the most divisive, challenging and ambitious endeavor that he had dared to tackle as Israel’s leader. Rightly or wrongly, Dimona, in Ben-Gurion’s eyes, was necessary to ensure that another Holocaust could never happen to Israel. If Kennedy had prevailed in his demand for biannual inspections, that goal might never have been obtained. For Ben-Gurion, abandoning Dimona would have cast a huge shadow on his legacy.

From a contemporary perspective, it is difficult, maybe impossible, to understand just how vulnerable and uncertain the future of the Dimona project was during the spring and summer of 1963. Had the United States been truly determined to suspend its “commitment to and support of Israel’s well-being” if Ben-Gurion did not comply with Kennedy’s demands – Israel probably would not have been able to complete the Dimona project as planned. The crisis was also a crisis of mutual confidence: Both sides were highly committed to their goals, but neither wanted to rupture the bilateral relationship. We will never know how unwavering President Kennedy would have been on the issue of Dimona, had he lived to serve his full term (or even two terms) as president. His resolve was never fully tested, although we can see that he was quite determined.

It turned out that Kennedy’s insistence on biannual visits to Dimona was not implemented. U.S. government officials remained interested in such a schedule, and President Lyndon B. Johnson did raise the issue with Eshkol, but he never pressed hard on the subject the way that Kennedy had.

In the end, the confrontation between President Kennedy and two Israeli prime ministers resulted in a series of six American inspections of the Dimona nuclear complex, once a year between 1964 and 1969. They were never conducted under the strict conditions Kennedy laid out in his letters. While Kennedy’s successor remained committed to the cause of nuclear nonproliferation and supported American inspection visits at Dimona, he was much less concerned about holding the Israelis to Kennedy’s terms. In retrospect, this change of attitude may have saved the Israeli nuclear program.

Avner Cohen is a professor of nonproliferation studies at the Middlebury Institute of International Studies at Monterey (California), and the author of “Israel and the Bomb.”

William Burr is a senior analyst at the National Security Archive, George Washington University, where he directs the Archive’s Nuclear Documentation Project and edits its web page The Nuclear Vault.