The pagers began beeping just after 3:30 Tuesday afternoon in Lebanon, alerting Hezbollah operatives to a message from their leadership in a chorus of chimes, melodies, and buzzes.

But it wasn’t the militants’ leaders. The pages had been sent by Hezbollah’s archenemy, and within seconds the alerts were followed by the sounds of explosions and cries of pain and panic in streets, shops and homes across Lebanon.

Powered by just a few ounces of an explosive compound concealed within the devices, the blasts sent grown men flying off motorcycles and slamming into walls, according to witnesses and video footage. People out shopping fell to the ground, writhing in agony, smoke snaking from their pockets.

Mohammed Awada, 52, and his son were driving by one man whose pager exploded, he said. “My son went crazy and started to scream when he saw the man’s hand flying away from him,” he said.

By the end of the day, at least a dozen people were dead and more than 2,700 were wounded, many of them maimed. And the following day, 20 more people were killed and hundreds wounded when walkie-talkies in Lebanon also began mysteriously exploding. Some of the dead and wounded were Hezbollah members, but others were not; four of the dead were children.

Israel has neither confirmed nor denied any role in the explosions, but 12 current and former defense and intelligence officials who were briefed on the attack say the Israelis were behind it, describing the operation as complex and long in the making. They spoke to The New York Times on the condition of anonymity, given the sensitivity of the subject.

The booby-trapped pagers and walkie-talkies were the latest salvo in the decades-long conflict between Israel and Hezbollah, which is based across the border in Lebanon. The tensions escalated after the war began in the Gaza Strip.

Iranian-backed groups including Hezbollah have long been vulnerable to Israeli attacks using sophisticated technologies. In 2020, for example, Israel assassinated Iran’s top nuclear scientist using an AI-assisted robot controlled remotely via satellite. Israel has also used hacking to stymie Iranian nuclear development.

In Lebanon, as Israel picked off senior Hezbollah commandos with targeted assassinations, their leader came to a conclusion: If Israel was going high-tech, Hezbollah would go low. It was clear, a distressed Hezbollah chief, Hassan Nasrallah, said, that Israel was using cellphone networks to pinpoint the locations of his operatives.

“You ask me where is the agent,” Nasrallah told his followers in a publicly televised address in February. “I tell you that the phone in your hands, in your wife’s hands, and in your children’s hands is the agent.”

Then he issued a plea.

“Bury it,” Nasrallah said. “Put it in an iron box and lock it.”

He had been pushing for years for Hezbollah to invest instead in pagers, which for all their limited capabilities could receive data without giving away a user’s location or other compromising information, according to U.S. intelligence assessments.

Israeli intelligence officials saw an opportunity.

Even before Nasrallah decided to expand pager usage, Israel had put into motion a plan to establish a shell company that would pose as an international pager producer.

By all appearances, BAC Consulting was a Hungary-based company that was under contract to produce the devices on behalf of a Taiwanese company, Gold Apollo. In fact, it was part of an Israeli front, according to three intelligence officers briefed on the operation. They said at least two other shell companies were created as well to mask the real identities of the people creating the pagers: Israeli intelligence officers.

BAC did take on ordinary clients, for which it produced a range of ordinary pagers. But the only client that really mattered was Hezbollah, and its pagers were far from ordinary. Produced separately, they contained batteries laced with the explosive PETN, according to the three intelligence officers.

The pagers began shipping to Lebanon in the summer of 2022 in small numbers, but production was quickly ramped up after Nasrallah denounced cellphones.

Some of Nasrallah’s fears were spurred by reports from allies that Israel had acquired new means to hack into phones, activating microphones and cameras remotely to spy on their owners. According to three intelligence officials, Israel had invested millions in developing the technology, and word spread among Hezbollah and its allies that no cellphone communication — even encrypted messaging apps — was safe anymore.

Not only did Nasrallah ban cellphones from meetings of Hezbollah operatives, he ordered that the details of Hezbollah movements and plans never be communicated over cellphones, said three intelligence officials. Hezbollah officers, he ordered, had to carry pagers at all times, and in the event of war, pagers would be used to tell fighters where to go.

Over the summer, shipments of the pagers to Lebanon increased, with thousands arriving in the country and being distributed among Hezbollah officers and their allies, according to two American intelligence officials.

To Hezbollah, they were a defensive measure, but in Israel, intelligence officers referred to the pagers as “buttons” that could be pushed when the time seemed ripe.

That moment, it appears, came this week.

Speaking to his security Cabinet on Sunday, Prime Minister Benjamin Netanyahu said he would do whatever was necessary to enable more than 70,000 Israelis driven away by the fighting with Hezbollah to return home, according to reports in Israeli news outlets. Those residents, he said, could not return without “a fundamental change in the security situation in the north,” according to a statement from the prime minister’s office.

On Tuesday, the order was given to activate the pagers.

To set off the explosions, according to three intelligence and defense officials, Israel triggered the pagers to beep and sent a message to them in Arabic that appeared as if it had come from Hezbollah’s senior leadership.

Seconds later, Lebanon was in chaos.

With so many people wounded, ambulances crawled through the streets, and hospitals were soon overwhelmed. Hezbollah said at least eight of its fighters were killed, but noncombatants were also drawn into the fray.

In southern Lebanon, in the village of Saraain, one young girl, Fatima Abdullah, had just come home from her first day of fourth grade when she heard her father’s pager begin to beep, her aunt said. She picked up the device to bring it to him and was holding it when it exploded, killing her. Fatima was 9.

On Wednesday, as thousands gathered in Beirut’s southern suburbs to attend an outdoor funeral for two people killed in the blasts, chaos erupted anew: There was another explosion.

Amid the acrid smoke, panicked mourners stampeded for the streets, seeking shelter in the lobbies of nearby buildings. Many were afraid that their phone, or the phone of a person standing next to them in the crowd, was about to explode.

“Turn off your phone!” some shouted. “Take out the battery!” Soon a voice on a loudspeaker at the funeral urged everyone to do this.

For the Lebanese, the second wave of explosions was confirmation of the lesson from the day before: They now live in a world in which the most common of communication devices can be transformed into instruments of death.

One woman, Um Ibrahim, stopped a reporter in the middle of the confusion and begged to use a cellphone to call her children. Her hands shaking, she dialed a number and then screamed a directive:

“Turn off your phones now!”

The New York Times Services