The meeting was so secret that only the attendees, a handful of top Iranian government officials and military commanders, knew the time and location.

It was June 16, the fourth day of Iran's war with Israel, and Iran's Supreme National Security Council gathered for an emergency meeting in a bunker 30 metres below a mountain slope in the western part of Tehran. For days, a relentless Israeli bombing campaign had destroyed military, government and nuclear sites around Iran, and had decimated the top echelon of Iran's military commanders and nuclear scientists.

The officials, who included President Masoud Pezeshkian, the heads of the judiciary and the intelligence ministry and senior military commanders, arrived in separate cars. None of them carried mobile phones, knowing that Israeli intelligence could track them.

Despite all the precautions, Israeli jets dropped six bombs on top of the bunker soon after the meeting began, targeting the two entrance and exit doors. Remarkably, nobody in the bunker was killed. When the leaders later made their way out of the bunker, they found the bodies of a few guards, killed by the blasts.

The attack threw Iran's intelligence apparatus into a tailspin, and soon enough Iranian officials discovered a devastating security lapse: The Israelis had been led to the meeting by hacking the phones of bodyguards who had accompanied the Iranian leaders to the site and waited outside.

According to Iranian and Israeli officials, Iranian security guards' careless use of mobile phones over several years — including posting on social media — played a central role in allowing Israeli military intelligence to hunt Iranian nuclear scientists and military commanders and the Israeli Air Force to swoop in and kill them with missiles and bombs during the first week of the June war.

"We know senior officials and commanders did not carry phones, but their interlocutors, security guards and drivers had phones; they did not take precautions seriously, and this is how most of them were traced," said Sasan Karimi, who previously served as the deputy vice president for strategy in Iran's current government and is now a political analyst and lecturer at Tehran University.

The security breakdowns with the bodyguards are just one component of what Iranian officials acknowledge has been a long-running and often successful effort by Israel to use spies and operatives placed around the country as well as technology against Iran, sometimes with devastating effect. Following the most recent conflict, Iran remains focused on hunting down operatives that it fears remain present in the country and the government.

Israel had been tracking senior Iranian nuclear scientists since the end of 2022 and had weighed killing them as early as last October but held off to avoid a clash with the Biden administration, Israeli officials said.

From the end of last year until June, what the Israelis called a "decapitation team" reviewed the files of all the scientists in the Iranian nuclear project known to Israel, to decide which they would recommend to kill. The first list contained 400 names. That was reduced to 100, mainly based on material from an Iranian nuclear archive that the Mossad, the Israeli intelligence agency, had stolen from Iran in 2018. In the end, Iran said the Israelis focused on and killed 13 scientists.

At the same time, Israel was building its capacity to target and kill senior Iranian military officials under a programme called "Operation Red Wedding". General Hajizadeh, the head of the Revolutionary Guards' air force, assembled his leadership team, accompanied by their security units, at the very start of the war to monitor intelligence about possible Israeli strikes. Israeli warplanes swooped in and carried out a pinpoint strike on the bunker where General Hajizadeh had taken refuge, killing him and other top commanders.

From the Israeli side, Iran's growing awareness of the threat to senior figures came to be seen as an opportunity. Fearing more assassinations on the ground of the sort that Israel had pulled off successfully in the past, the supreme Iranian leader, Ayatollah Ali Khamenei, ordered extensive security measures including large contingents of bodyguards and warned against the use of mobile phones and messaging apps like WhatsApp, which is commonly used in Iran. Those bodyguards, Israel discovered, were not only carrying cellphones but even posting from them on social media.

"Using so many bodyguards is a weakness that we imposed on them, and we were able to take advantage of that," one Israeli defence official said.

Iranian officials had long suspected that Israel was tracking the movements of senior military commanders and nuclear scientists through their mobile phones. Last year, after Israel detonated bombs hidden inside thousands of pagers carried by Hezbollah operatives in Lebanon, Iran banned many of its officials in particularly sensitive jobs from using smartphones, social media and messaging apps.

In 2021, according to three Israeli security officials, the focus turned to what Israeli officials called "the weapon group" — a cadre of Iranian scientists who the Israelis believed met regularly to work on building a device to trigger the enriched uranium and cause a nuclear explosion. This is one of the most technologically difficult parts of a nuclear project.

It was this group of scientists that became the focus of what Israel called Operation Narnia, the military plan to kill off scientists during the war's early days this spring.

By the time of the June 16 national security meeting of top Iranian officials, Israel had already killed a number of high-profile figures associated with the nuclear programme, including Tehranchi and Fereydoun Abbasi, another nuclear scientist, both killed just days earlier. The cellphones of their bodyguards helped Israel target all of them.

The ability to track the bodyguards also helped lead the Israelis to the June 16 meeting. The attendees, in addition to Pezeshkian, the Iranian President, included the speaker of Parliament, Gen. Mohammad Baqer Ghalibaf, and the head of the judiciary, Gholam-Hossein Mohseni-Ejei. Also on hand were the ministers of the interior, defence and intelligence and military commanders, some brand-new to their jobs after their bosses had been killed in previous strikes.

The attack destroyed the room, which soon filled with debris, smoke and dust, and the power was cut, according to accounts that emerged afterward. Pezeshkian found a narrow opening through the debris, where a sliver of light and oxygen was coming through, he has said publicly.

Three senior officials said the President dug through the debris with his bare hands, eventually making enough of a space for everyone to crawl out one by one. Pezeshkian had a minor leg injury from a shrapnel wound and the minister of interior was taken to the hospital for respiratory distress, officials said.

"There was only one hole, and we saw there was air coming and we said, we won't suffocate. Life hinges on one second," Pezeshkian said recently, recounting the attack in a meeting with senior clerics, according to a video published in Iranian media. He said if Israel had succeeded in killing the country's top officials it would have created chaos in the country.

"People," he said, "would have lost hope".

New York Times News Service