Canadians helped uncover Israel's secret nuclear weapons program, newly discovered papers from the mid-1960s have revealed, with a key role being played by a Department of National Defence intelligence analyst who was a churchgoing Mennonite committed to peace.

It was only in 1986, when a disgruntled Israeli technician named Mordechai Vanunu contacted the Sunday Times, that the public heard first-hand that Israel had been working on a nuclear arsenal for decades at a factory near the city of Dimona.

But as early as the 1960s, when the secret program was still at an experimental stage, Canadian intelligence officers discovered that Israel was buying at least 80 tonnes of uranium yellowcake from Argentina, and then helped Britain and the United States make sense of the discovery, declassified documents show.

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The latest revelations, based on little-known U.S. and British diplomatic files, were uncovered by two scholars, William Burr, an analyst at the Washington-based National Security Archive, and Avner Cohen, a professor at the Monterey Institute of International Studies.

The documents reveal that a DND analyst in Ottawa was remarkably prescient in predicting how Israel was developing a nuclear military capacity. They also shine a light on the inner working of Canadian security forces during the Cold War and expose the tensions between the two North American allies as the Canadians struggled to persuade the Americans to share information and treat them as equals, Dr. Cohen said in an interview.

Construction at the Dimona facility, in the Negev desert, began after Israel and France signed a nuclear co-operation agreement in 1957.

The documents unearthed by Dr. Burr and Dr. Cohen show that by 1960, American officials had discovered that what Israel previously described as a textile plant and later a metallurgical plant in Dimona was instead a nuclear reactor. The Americans however had no conclusive evidence that it was used for a military aim.

Israel has never admitted to this day that it has a nuclear arsenal, strategically leaving the matter ambiguous. In their dealings with western powers in the early 1960s, Israeli officials said their nuclear project was a peaceful endeavour but made sure they would be taken seriously by suggesting that they could quickly move their program to military ends, Dr. Cohen said.

According to a March 1964 memo to White House advisor McGeorge Bundy, during a state visit to Canada in May 1961, Israel's Prime Minister, David Ben Gurion, told his Canadian counterpart, John Diefenbaker, that Israel "might" have to develop a nuclear weapon if its defensive capability were to become heavily outweighed. Ben Gurion conveyed a similar message to U.S. President John Kennedy.

By early 1964, according to cables from the U.S. embassy in Paris, the French stopped shipping uranium to Israel. Worried that a bomb would be manufactured, the French wanted Israel to purchase nuclear fuel solely from them so Paris could retain "some control over [the] situation" in Dimona -- but the Israelis balked.

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Around the same time in Ottawa, DND intelligence analyst Jake Koop wrote a paper arguing that Israel likely had a military nuclear capacity.

Then 40, Mr. Koop was a Mennonite, a pacifist Christian denomination. Many Mennonites were conscientious objectors during the Second World War but Mr. Koop chose to enlist in the Canadian army and served in Holland and Germany. He told his family that he prayed he wouldn't have to kill anyone and was grateful his prayers were answered, his daughter Barbara recalled in an interview.

In 1951, Mr. Koop joined DND, analyzing issues relating to nuclear weapons proliferation for the Defence Research Board. At the same time, he was a charter member and deacon of the Ottawa Mennonite Church.

He was convinced that working for DND, especially on scientific matters, could contribute to arms control and disarmament, a friend, Bill Janzen, said in an interview. "He was strongly committed to peace ... His career path was certainly unusual for a Mennonite, being active at a high level at DND."

In his report, submitted in March 1964, Mr. Koop underlined that Israel had two distinct nuclear programs: a small civilian research unit, and a larger, secretive one that likely was a first step in developing weapons.

Mr. Koop predicted that Israel could conduct an initial nuclear test by 1966 and could develop a "limited nuclear weapons capability" of six to 10 low-yield bombs by the end of 1968. His forecast wasn't far off. Israel built its first nuclear devices shortly before the 1967 Six-Day War, Dr. Cohen said.

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Sometime around the period Mr. Koop penned his report, Canadian intelligence learned that the Israelis had found a new source of nuclear material to replace the French restrictions.

This is revealed in an April 1964, letter from Alan Goodison, a Foreign Office analyst in London, to the embassies in Buenos Aires, Cairo, Paris, Washington and Tel Aviv.

"Canadian Intelligence authorities have informed the Defence Intelligence Staff that the Argentine Republic and Israel have signed an agreement for the sale of the entire Argentine production of uranium concentrate to Israel. This involves the transfer of 80-100 tons over 33 months. This means that Israel now has virtually unlimited supplies of uranium free of safeguards," Mr. Goodison wrote.

He added: "Their anxiety to obtain such a large quantity of safeguard-free uranium suggests that they have sinister motives. Although the evidence is all circumstantial it is beginning to be overwhelming."

He said the Canadians were reluctant to share their discovery with the U.S. because the Americans had refused them information on their recent inspection of Dimona. "I have suggested to the Canadian High Commissioner here that this is perhaps short-sighted."

The letter does not identify the Canadian intelligence outfit. Wesley Wark, a professor at the University of Ottawa's Graduate School of Public and International Affairs, said the material likely came from the now defunct Joint Intelligence Bureau.

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Created after the Second World War, the JIB was an independent unit that was nominally attached to DND. Dr. Wark said it was run for many years by a former British intelligence officer, Ivor Bowen, and worked very closely with its UK counterpart, which was headed by Mr. Bowen's former boss, Kenneth Strong.

"During the 1960s, the JIB developed an economic intelligence function and it was likely in that capacity that this very secretive outfit acquired information about the purchase of Argentinian uranium," Dr. Wark said.

In June 1964, an officer at the British embassy in Buenos Aires, wrote to London, saying that E.R. Bellemare, the chargé d'affaires at the Canadian embassy, "confirms that the information supplied by the Canadian intelligence authorities did not originate in Buenos Aires. He is, however, in fairly close touch with the Argentine National Atomic Energy Commission which has volunteered information to him that the Commission has recently made sales of uranium concentrate both to Israel and West Germany."

By the end of June, the Canadians had agreed to pass their tip to the Americans. The CIA and the Deparment of State sent a joint query to U.S. missions in Tel Aviv and Buenos Aires, asking for more information about the sale.

In September, the U.S. embassy in Buenos Aires got a confirmation from an Argentine official of an 80-tonne yellowcake deal with Israel. The Americans then tried to query Israel further but only got evasive answers, Dr. Cohen said.

Later that fall, the military attaché at the Canadian embassy in Tel Aviv gave a copy of Mr. Koop's analysis to British diplomats. The report was sent in a locked box to London. An accompanying note from a counselor at the British Embassy in Tel Aviv praised Mr. Koop's work as a "a model of what these things should be."

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The copy was shown to R.C. Treweeks, a British defence analyst, who replied in December that the Canadian paper "is, in my opinion, extremely well organized, makes the most of the basic material available and, as far as we can see, leaves none outstanding."

Mr. Koop died on July 2, 2009. His family marked the fourth year of his death with a photo and a notice in the obituary page of the Ottawa Citizen. But until a Globe and Mail reporter contacted them earlier this month, they were not aware of his much-praised work on Israel's nuclear weapons program.