A year before the 1967 Six Day War, a Jewish-American scientist reportedly gave Israel groundbreaking technology that facilitated eavesdropping on secret communications between the surrounding Arab nations, ultimately leading to a decisive victory.

Just before he died last July, nuclear scientist Zalman Shapiro told a reporter from Pittsburgh’s Tribune-Review that he gave Israel advanced batteries that could be used for long-distance surveillance.

Shapiro’s company, Nuclear Materials and Equipment Corp. (NUMEC), used radioactive strontium 90 to create batteries with an extremely long life for the US military. The batteries, called radioisotope thermoelectric generators, could operate at extreme temperatures and even underwater, using the heat generated by the radioactive decay of the strontium (or other radioactive materials) to generate electricity.

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Shapiro said that in 1966 the then-head of the Mossad, Meir Amit, contacted him to ask if he could supply the batteries to be used in spy stations on the Egyptian border.

“He smelled a rat with regard to Egypt and what they planned to do,” Shapiro told the Tribune-Review, and only the nuclear batteries were powerful enough to get the information that Israel desperately needed.

Shapiro said the batteries were used to listen in on radio transmissions from across the border.

“The batteries had to be strong enough to convey the information and had to have a range to pick up what the Egyptians were saying to their allies,” he said.

Shapiro said that his company also sent at least one engineer to Israel to ensure the batteries were working properly.

Zalman Shapiro, nuclear scientist who founded NUMEC in Apollo, died Saturday at age 96. https://t.co/LhaSCsBXd6 pic.twitter.com/yF5YzaaiE1 — ValleyNewsDispatch (@VNDNews) July 19, 2016

Shapiro told the Tribune-Review that he had supplied Israel with batteries for other top-secret projects, but would not provide details, saying the information was still classified.

Oscar Gray, NUMEC’s former vice president, told the Tribune-Review that he suspected the batteries were being used for spying, but the Israelis claimed they needed the batteries for weather-monitoring devices. They said “it was to power long-usage monitors out in the desert for rainfall,” he recalled.

After the war, Israel went back to Shapiro for a different kind of battery. A senior Mossad official at the time, Rafi Eitan, visited NUMEC in Pennsylvania in 1968, saying he needed batteries for wiretapping devices.

“With the batteries, I could listen to you in my living room for two years,” Eitan told the Tribune-Review. “At that time, in the 1960s, when I did visit the plant, there were very few who could produce (the batteries) in the world.”

Shapiro’s admission that he gave Eitan nuclear batteries revives a decades-old rumor that Shapiro gave Israel the uranium it used to start its secret nuclear program.

It was alleged that some 90 kilograms (200 pounds) of enriched uranium disappeared from NUMEC and ended up in Israel. Both the Atomic Energy Commission and the FBI investigated the missing nuclear fuel, but no charges were ever filed.

A former Pentagon official said in 1986 that there was “no conceivable reason for Eitan to have gone (to the Apollo plant in 1968) but for the nuclear material.”

Gray rejected the claim that NUMEC ever sent uranium to Israel.

“What you got are a couple of guys from the CIA and FBI who knew very little about the subject, very little about it,” he said. “They got excited because it looked like there was a big mystery here, and Shapiro was a big supporter of Israel.”