"When Marwan spoke, the highest leaders in Israel within a matter of hours got the transcripts of what he spoke. Golda Meir read them, Moshe Dayan read them. The army chief of staff read them. And this is how they formed their opinions," author Howard Blum explained.
"We were very, very sensitive and aware about early warning of an enemy attack on Israel. From the first day, this was rule number one," Levran told Kroft.
"And you relied on Marwan to give it to you?" Kroft asked.
"Of course," Levran said.
According to the Egyptians, it was Israel's reliance on Marwan to warn them of an impending attack that allowed their army and the Syrians to amass hundreds of thousands of troops on Israel's borders in the fall of 1973, under the guise of a training exercise. In fact, the Yom Kippur War was about to begin, and the Israelis had heard nothing from Marwan.
"Who was Ashraf Marwan working for?" Kroft asked Dr. Abdel Monem Said, one of Egypt's top national security experts.
"He was officially working for the president of Egypt. But also, he was working for the security establishment of Egypt as well," Said told Kroft.
Dr. Said said it was all part of the plan.
Said told Kroft Marwan didn't work for the Israelis. "Not whatsoever," he said.
Egyptian officials refused to talk to 60 Minutes about Marwan on camera because the information is still secret.
But a number of people directed us to Said for the Egyptian side of the story, which is that Israel's greatest spy was actually a double agent.
"Top Israelis told us 'Marwan gave us the best information we have ever gotten from anyone,'" Kroft told Said.
"How you build the confidence in one of the best intelligence services in the world? You give them best information that serve your purpose," he replied.
The Egyptians' purpose was to recapture the Suez Canal and all or part of the 23,000 square miles of the Sinai Peninsula occupied by the Israelis. To do it, they needed to deceive their enemy at a crucial moment, and according to Dr. Said, Marwan was the key element in that deception.
"The Israeli know that there was Egyptians and Syrians on the ground mobilizing their forces. These forces were already in the front. They are taking offensive positions," Said explained. "It's a classic case in the books. You got all the information, but you make the wrong interpretation. And the only variable that is different was Ashraf Marwan."
"We were subjugated to this source, and we put aside information from the observation posts we were dependent on him to give us the last verdict. The last confirmation," Aharon Levran told Kroft.
Marwan finally provided that confirmation at a late-night meeting in London with the head of Mossad, just 12 hours before the fighting began. The Syrians and the Egyptians would attack on two fronts, he said, at 6 p.m. the following day, the holiest day on the Jewish year. The Israelis were totally unprepared. Most of their soldiers were already home with their families.