Israel’s nuclear posture is unique. Some countries with “advanced nuclear capabilities,” such as India and China, have publicly adopted “No First Use” postures. Israel has adopted a declaratory policy that it will not be the first to “introduce” nuclear weapons into the Middle East. This posture has been met with widespread and willing suspension of disbelief, as it serves many useful purposes. How did the “NFI” posture come about? And has its meaning evolved over time?

Avner Cohen has produced the most complete account we now have of Israel’s NFI posture in his fine book, Israel and the Bomb. The key junctures of NFI, as chronicled by Cohen are as follows:

1. A meeting between President Kennedy and Deputy Minister of Defense Shimon Peres on April 2, 1963. Kennedy pressed Peres hard to offer assurances that would support the President’s nonproliferation agenda. According to U.S. notes of the meeting, Peres said the following:

“I can tell you most clearly that we will not introduce nuclear weapons to the region, and certainly we will not be the first.” The meeting with Kennedy was called on short notice, and Peres apparently improvised this answer, much to the discomfort of other Israeli leaders. When asked to recollect about this exchange in 1991, Peres said, “I did not want to lie to the President, but I could not answer his question straight, either. So I came up with what has become Israel’s policy for years to come.”

2. A Memorandum of Understanding reached on March 10, 1965 between Prime Minister Levi Eshkol and NSC official Robert Komer and U.S. Ambassador to Israel Walworth Barbour. In this MOU, the U.S. “reaffirmed its concern for the maintenance of Israel’s security” and to the “independence and integrity” of Israel. In return, “the Government of Israel has reaffirmed that Israel will not be the first to introduce nuclear weapons into the Arab-Israel area.”

3. An address to the Knesset by Eshkol on May 18, 1966, in which the Prime Minister stated, “I have said before and I repeat that Israel has no atomic weapons and will not be the first to introduce them into our region.”

Cohen’s careful account of this nuclear history includes very few attempts by U.S. officials to clarify the meaning of Israel’s NFI pledge. The principle exception occurred in the Johnson administration, which negotiated and championed the NPT. Paul Warnke, then a high-ranking Pentagon official, was under instructions from Secretary of Defense Clark Clifford and Secretary of State Dean Rusk to try to add definition and constraints to Israel’s NFI pledge. Warnke met several times with Israeli Ambassador Yitzhak Rabin in November 1968, where these two men engaged in an oblique, yet crucial discussion about the meaning of Israel’s NFI pledge. Whatever leverage Warnke had was in the form of F-4s, which Israel desperately wanted. Rabin, who was without instructions, spoke extemporaneously. He suggested that the NFI pledge be characterized in terms of not testing nuclear weapons and not publicly declaring their possession. Warnke sought to expand Rabin’s offerings to include “physical possession.” (The State Department held out the vain hope in the Johnson administration that Israel could sign the NPT under its NFI pledge.) Rabin rejected physical possession as a constituent element of Israel’s NFI pledge. U.S. notes of the November 12, 1968 meeting has Warnke summarizing this discussion as follows: “In your view, an unadvertised, untested nuclear device is not a nuclear weapon.” Rabin’s response was, “Yes, that is correct.”

LBJ granted the sale of F-4s to Israel, and Israel did not sign the NPT. End of story? Not quite.

Two signal events have raised further questions about Israel’s NFI pledge. Just prior to the Six Day War in 1967, Israel is reliably reported to have readied a small number of nuclear weapons for operational use, if necessary. Missiles capable of delivering nuclear weapons were also readied for use. This helps to explain Rabin’s refusal to endorse Warnke’s formulations, but it highly qualifies Israel’s NFI pledge.

Then there is Rabin’s unqualified “no test” pledge. On September 22, 1979, U.S. monitoring capabilities registered data suggestive of a low-yield nuclear event in the South Atlantic. One possibility was an Israeli test in collaboration with the Government of South Africa, or some variation thereof. A distinguished panel of U.S. technical experts, led by Jack Ruina, which included Dick Garwin Wolfgang Panofsky, and Luis Alvarez, poured over these data and gave Israel the benefit of the doubt. A new book by Thomas C. Reed and Danny B. Stillman, The Nuclear Express, paints a very different picture. Reed and Stillman’s book contains factual errors and unsupported assertions, but their account of the South Atlantic event cannot be summarily dismissed.

Avner Cohen, who knows more about Israel’s nuclear program than anyone else writing on the subject, treats this matter only inferentially, and with tortured logic:

Politically, the first full-yield nuclear test signifies the transition from secrecy to the public phase. A test provided a clear cut and visible criterion for recognizing when and how the nuclear threshold had been crossed. Nuclear proliferation was thus perceived as an either/or process: as long as a country did not conduct a full-yield test it was still given the benefit of the doubt concerning its nuclear status. Israel made its nuclear pursuit piecemeal and by taking advantage of this conceptualization of the proliferation process.

A great many nuclear weapon tests have been carried out at less than full yield – including the Indian, Pakistani, and North Korean tests. If Israel has participated in such a test well beyond the Middle East, does this accord with its NFI pledge?