The Yom Kippur War, which began on October 6, 1973 and would become the most intense military clash in the history of the Arab-Israeli conflict, is usually thought of as a surprise attack. Yet for a full week before Egypt and Syria went to war, Israeli Military Intelligence (MI) had detected a dramatic increase in unusual military activity on Israel’s borders along the Golan Heights and the Suez Canal. Growing evidence that war was imminent, however, was dismissed by the director of MI, Maj. Gen. Eli Zeira, who remained convinced that despite indications on the ground, Syria would never attack without Egypt, and Egypt would never attack without the weapons needed to neutralize Israel’s air superiority. As the chief interpreter of intelligence for Israeli decision-makers, he made sure his opinions were shared, emphatically, with Defense Minister Moshe Dayan and Prime Minister Golda Meir.

And then, on Thursday, October 4, the USSR began an emergency airlift to evacuate thousands of Soviet officers and their families from Egypt and Syria. Israeli leaders held a series of emergency meetings in Tel-Aviv the following day—the eve of Yom Kippur—in which Golda Meir expressed her alarm about a possible Arab attack. Zeira, however, stuck to his guns. Believing that prior to any Arab attack they would get clear warnings, the cabinet reached a compromise: The regular army was put on its highest state of alert, but there would be no mobilization of reserves, who constituted 80 percent of the IDF’s ground forces. As the sun headed to the sea and thoughts turned to the coming day of prayer and fasting, Israel’s leaders hoped they had averted disaster.

They had not. Ashraf Marwan, the son-in-law of the late Egyptian leader Gamel Abdel Nasser and aide-de-camp of Egyptian President Anwar Sadat, had secretly provided intelligence to the Mossad since 1970. For some time now, he had been warning the Israelis that Sadat wasn’t bluffing about a massive coordinated attack. But after too many leaks of Sadat’s previous plans, Sadat had kept the precise day and time of the attack almost entirely to himself. Understanding that war was close, Marwan, who was traveling in Paris on Thursday, October 4, signaled to his handler in the Mossad, whom we know only as “Dubi,” demanding an urgent meeting in London with the chief of the Mossad, Zvi Zamir. Zamir took the first flight to London the next morning.

Marwan made his way to London as well. There he learned from a friend who worked for EgyptAir that the airline had received orders to reroute their civilian aircraft to safer locations—orders that were then abruptly rescinded. This was all Marwan needed to hear. From his hotel room he made a few calls to colleagues in Egypt, and by noon on Friday he was certain that the attack plans had finally been set in motion.

The secure arrangement of a meeting with the Mossad chief and Dubi, however, would take some time. The hours ticked away on Friday, October 5, into the night of Yom Kippur.

From The Angel: The Egyptian Spy Who Saved Israel:

It was close to 10 p.m. London time when Dubi and Zamir reached the apartment where the meeting would be held. Mossad agents, who had been in place for several hours, gave the area around the building a final once-over. Dubi and Zamir went in and waited. It was a long wait. Marwan had rarely been late before. Slightly after 11:30 p.m., they finally heard a knock on the door. Dubi opened it, and in walked the Angel.

Handshakes and formalities were exchanged. Dubi took a seat near the large dining table, notebook open and pen in hand. Marwan sat in an armchair by the coffee table, facing Zamir.

This was the first meeting between Marwan and his handlers since the failed attack on the El Al jet in Rome a month earlier. The Israelis wanted to make sure their source hadn’t been compromised, and they wanted him to know they were concerned. This is why Zamir’s first line of questioning was about whether any suspicions had been raised after the Italian forces raided the apartment in Ostia—a raid that clearly was based on advance warning—and whether Sadat had shown any interest in the question of how the Italians knew about the attack. Marwan reassured them that the episode had not caused him any trouble. Sadat probably figured that Marwan had tipped the Italians off; since the terror attack wasn’t in Egypt’s interest anyway, this in itself was unlikely to trouble the president. But nobody suspected he had said anything to the Israelis.

From the abrupt manner in which he deflected Zamir’s questions, however, it was clear that Marwan had something more pressing on his mind.

Marwan was tense. “I have come here,” he announced, “to talk about the war, and nothing else. I came late because I have spent the entire evening at our consulate in Kensington. I’ve been on the phone with Cairo, trying to get the most up-to-date information. He [Sadat] intends to go to war tomorrow.” From the way Marwan expressed himself in what followed, one gets the sense that he thought the Israelis already knew about it. It was a belief held widely by the Egyptians that the Israelis would know about the attack two full days before it was launched. But it is also possible that he was trying to gloss over the fact that—despite presenting himself to the Israelis as the oracle of all knowledge worth knowing in Egypt—here he now was, less than 24 hours before the attack, having learned about it only a few hours earlier.

Zamir was taken by surprise. He had come to the meeting worried because from the latest information he had, especially the Soviet evacuations, he could see that Egypt and Syria were heading for war. But he had not imagined that the attack would be launched in less than 24 hours. And he was also worried that, just as with past warnings, this one, too, would prove a false alarm. So his immediate response was, “On what do you base your assertion?”

For Marwan, who had previously given false alarms of war, both his credibility in the eyes of the Israelis and his image as a central player in Cairo were obviously important. Nor is it clear where he got his information—to whom, in other words, he had made those phone calls throughout the evening. And because his information was based on telephone conversations rather than face-to- face meetings, it is fair to assume that what he heard had been phrased cautiously or even ambiguously. He had not spent the crucial days before the war in Sadat’s presence, so he couldn’t know what the atmosphere was like in the presidential offices, where there were people who already knew the secret. The dissonance between the information he had received, in whose credibility he had no doubt, and his intimate knowledge of Sadat’s psyche—the president had changed his mind many times about the date of attack—had its effect on him. The more Zamir pressed him to give his own independent take on whether war would in fact erupt the next day, the more Marwan grew agitated, at least once raising his voice. “How should I know?” he shouted. “He [Sadat] is crazy. He can march forward, tell everyone else to march forward, and then suddenly march backward.” Marwan was giving voice not only to his frustration at his inability to give a straight answer to the most important question of his career as a spy, but also to his personal aversion toward Sadat, his inclination to disrespect him and see him as unreliable.

Zamir was less worried about Marwan’s inner conflict than about whether or not a war would start the next day. He had been a senior IDF officer in 1959, when a poorly thought-out military exercise involving an unannounced, emergency mass call-up of reserves instilled fear in an entire nation, triggered the call-up of reserves in Egypt and Syria in response, and ratcheted up tensions in the whole region. The affair, known as the Night of the Ducks, brought an end to the military careers of the commander of the IDF’s operations branch, Maj. Gen. Meir Zorea, and the chief of military intelligence, Maj. Gen. Yehoshafat Harkabi. Images of that episode flashed through Zamir’s mind as he spoke with Marwan. The Night of the Ducks, he realized, would look like child’s play compared with a mistaken emergency mobilization for war in the middle of Yom Kippur. He could see the worldwide reaction to the IDF pulling tens of thousands of reserve soldiers out of the synagogues and sending them to the front to await an Arab onslaught that never came. The price would be incalculable. Now was the time, Zamir knew, to press his source as hard as possible, to make sure the warning was well grounded.

Marwan’s discomfort did little to quell Zamir’s concerns. He quickly realized that he’d have to rely on his own experience, which was much greater than Marwan’s, to formulate his own opinion. Zamir didn’t know what had happened in Israel since his departure to London, but he had no reason to think that the reserves had already been called up. He understood that a clear warning that war would be launched the next day would leave the decision makers without any alternatives to a full-blown emergency call-up. And so, despite his being the chief of the Mossad and not the prime minister and her cabinet, he suddenly felt the full weight of the government’s decision on his shoulders. But Zamir was himself a former general, having previously served as the chief of the IDF Southern Command, and he fully understood the implications of trying to fend off an Arab assault without calling up reserves.

By the end of the meeting, he had already made up his mind. He would send back to Israel an unambiguous warning that Egypt and Syria planned on launching a full-scale attack the next day.

This decision would alter the course of the Yom Kippur War.

But he wasn’t finished with Marwan. Next, he grilled him about the war plans. Marwan hadn’t brought any documents with him, but most of the key details of the latest battle plans were burned in his memory and had just been reconfirmed by his contacts in Cairo. Nothing had changed since the last time he’d passed the most recent version of the war plans to his handlers several weeks before. Egyptian infantry divisions would cross the Suez Canal and move farther east up to six miles. He went into some detail about the air and commando raids aimed at blocking IDF reinforcements heading for the front. Marwan also confirmed that the Egyptian air force would send its Tupolev Tu-16 bombers armed with Kelt missiles to strike the IDF headquarters in Tel Aviv. This, too, had appeared in the plans he had previously passed along.

Zamir also asked about the precise hour of attack (H-hour), though he didn’t consider it such a pressing question. In all of the Egyptian battle plans that Israel had seen for years, H-hour was precisely sunset—a time that left just enough daylight to carry out a major air assault on the Sinai, before darkness came to preclude an effective response by the Israeli Air Force. According to Marwan’s report, that would be the plan this time as well. On October 6, 1973, the sun would set at 5:20 p.m. Israel time.

What neither Marwan nor his handlers knew, however, was that two days earlier, the Egyptian war minister had met with the president of Syria and had agreed to launch the attack at 2 p.m., as a compromise between Syrian and Egyptian operational needs.

The meeting lasted more than two hours. Marwan returned to his hotel, with Mossad agents keeping tabs on him. The next day, Saturday, he went back to Egypt. Zamir and Dubi, who had spent the whole meeting writing down every word, went directly to the home of the Mossad’s London station chief, a ten-minute walk. On the way, Zamir wondered aloud what would happen if he sent a warning of immediate war and the war never came. He didn’t need to wait for Dubi’s answer, however. He had already made up his mind.

They reached the apartment of Rafi, the station chief, who was waiting for them. Zamir took a few minutes to carefully craft, longhand, the coded message that he would send to his chief of staff, Freddy Eini, who waited at home in Israel. Also present was Zvi Malhin, who was responsible for security for the meeting with Marwan. When Malhin saw the message Zamir had written, he reminded him of the Night of the Ducks of 1959, as if Zamir needed reminding, and what happened to those responsible. But Malhin, too, was convinced that war was coming: A few hours before war started, he called his wife in the Afeka neighborhood of Tel Aviv, and told her to find a neighbor’s house with a bomb shelter where she could take cover. Their own house didn’t have one.

Zamir called Freddy Eini. By 1973, direct dial had been introduced between London and Israel, and there was no need for an international operator. It was now close to 3 a.m., exactly 24 hours after Eini had called Zamir to tell him that the Angel wanted an urgent meeting in London to talk about chemicals. It was extremely important to Zamir that Eini now understand every word he said, and that he move as quickly as possible to implement what was included in the message. When Eini answered, Zamir first told him, “Put your feet in cold water”—that is, be wide awake, right now. Once Eini had assured him he was fully alert, Zamir dictated to him the message as he had written it down.

It read as follows, in full:

The company, it turns out, intends to sign the contract today before nightfall.

It is the same contract, with the same conditions with which we are familiar.

They know that tomorrow is a holiday.

They think they can land tomorrow before dark.

I spoke with the manager, but he cannot put it off because of his commitment to other managers, and he wants to keep his commitment.

I’ll update you on all the conditions of the contract.

Because they want to win the race, they are very afraid that it will be made public before the signing, for there may be competitors, and then some of the shareholders will think twice.

They have no partners outside the region.

In the Angel’s opinion, the chances of signing are 99.9 percent, but then again, he is like that.

Meanwhile Dubi prepared a communiqué about the meeting. When he was done, he went to the Israeli embassy at Palace Green in central London in order to send it via the code room. According to some accounts, because of Yom Kippur no one was on duty in the code room, and they had to wait for someone to show up. In truth, however, the station chief was there waiting for him, and the report was sent to Mossad headquarters in Tel Aviv during the early morning hours. The communiqué repeated Zamir’s alert that war would commence later that day and added that the source had said that Sadat might change his mind at the last minute. Beyond this, the main message was that the Egyptian war objective was limited only to capturing territory up to six miles east of the Suez Canal, and that at this stage there was no intention to advance to the Mitla and Gidi Passes.

Dubi went back to his apartment. His wife, Ronit, was waiting. She was used to his unpredictable schedule, but his long absence in the middle of the night of Yom Kippur was unusual even for him, and it suggested something serious. She didn’t have to ask many questions. With her, he could be explicit. “It’s war. The bar mitzvah’s off.”

Their son Ofer had come of age, and his bar mitzvah celebration, which was supposed to take place soon after, was one of Israel’s first, if least painful, casualties in the conflict that would begin in just a few hours. Later that morning, utterly exhausted, Dubi finally went to bed.

The Angel: The Egyptian Spy Who Saved Israel by Uri-Bar Joseph © 2016 by Uri Bar Joseph. Excerpted with permission of Harper, an imprint of HarperCollins Publishers.

Uri Bar-Joseph is a professor of political science at the University of Haifa, Israel, and one of the world’s experts on Israeli intelligence, having served for more than 10 years as an active-duty and a reserve-duty intelligence analyst in the IDF (Israeli Defense Force) Intelligence/Research Division. He earned his Ph.D. from Stanford University.