WASHINGTON — Secret Service officers made a critical discovery this spring after locating Ayman al-Zawahri, the leader of al Qaeda, in Kabul, Afghanistan: He liked to read alone on the balcony of his safe house early in the morning.
Analysts are looking for this kind of life pattern intelligence, any habit the CIA can exploit. In al-Zawahri’s case, his long visits to the balcony gave the agency an opportunity for a clean missile strike that could avoid collateral damage.
The hunt for al-Zawahri, one of the world’s most wanted terrorists, stretches back to before the 9/11 attacks. The CIA continued to search for him as he rose to the top of al-Qaeda after the death of Osama bin Laden and after the Taliban took over Afghanistan last year. And one mistake, the hiring of a double agent, led to one of the bloodiest days in the agency’s history.
Immediately after the United States withdrew from Kabul, the CIA intensified its efforts to find al-Zawahri, convinced that he would try to return to Afghanistan. Senior officials had told the White House that they could maintain and establish intelligence networks inside the country from afar and that the United States would not be blind to terrorist threats there. For the agency, finding al-Zawahri would be a key test of that claim.
This article is based on interviews with current and former US and other officials, independent analysts who have studied the decades-long hunt and others briefed on the events leading up to the weekend strike. Most spoke on condition of anonymity because of the sensitive intelligence used to find al-Zawahri.
For years al-Zawahri was believed to be hiding in the border region of Pakistan, where many Qaeda and Taliban leaders fled after the US invasion of Afghanistan in late 2001. He was wanted in connection with the 1998 embassy bombings in Tanzania and Kenya. and the CIA had tracked a network of people that intelligence officials thought were supporting him.
Scrutiny of that network has intensified with the US withdrawal from Afghanistan last year and the belief by some intelligence officials that senior al Qaeda leaders will be tempted to return.
The hunch turned out to be correct. The agency found that al-Zawahri’s family had returned to a safe house in Kabul. Although the family tried to ensure they were not tracked and to keep al-Zawahri’s location a secret, intelligence soon learned that he too had returned to Afghanistan.
“There was a renewed effort to figure out where he was,” said Mick Mulroy, a former CIA officer. “The only good thing that could come from pulling out of Afghanistan is that some high-level terrorist figures would then think it’s safe for them to be there.”
The safe house was owned by an aide to senior officials in the Haqqani network, a hard-line and violent wing of the Taliban government, and was located in an area controlled by the group. Senior Taliban leaders occasionally met at the home, but U.S. officials do not know how many knew the Haqqani were hiding al-Zawahri.
If some senior Taliban officials were unaware that the Haqqani had allowed al-Zawahri to return, his killing could drive a wedge between the groups, independent analysts and others briefed on the matter said.
It is not clear why Al-Zawahri returned to Afghanistan. He had long made recruitment and promotional videos and it might have been easier to produce them in Kabul. He may also have had better access to medical care.
Regardless of the reason, his ties to leaders of the Haqqani network led US intelligence officials to the safe house.
“The Haqqanis have a very long-standing relationship with al-Qaeda going back to the mujahideen era,” said Dan Hoffman, a former CIA officer. “They provide al Qaeda with a lot of tactical support that they need.”
Once the safe house was located, the CIA followed the book he wrote during the hunt for bin Laden. The agency built a model of the site and tried to learn everything about it.
Analysts eventually identified a figure who remained on the balcony reading, but never left the house, as al-Zawahri.
American officials quickly decided to target him, but the location of the house posed problems. It was in the Sherpur neighborhood of Kabul, an urban area with houses in close proximity. A missile armed with high explosive could damage nearby houses. And any kind of incursion by Special Operations forces would be prohibitively dangerous, limiting the options for the US government to launch a strike.
The search for al-Zawahri was of enormous importance to the agency. After the US invasion of Afghanistan, the CIA base in Khost province became home to a targeting team dedicated to tracking both bin Laden and al-Zawahri. It was one of the leads the CIA developed to locate al-Zawahri that proved disastrous for the agency’s officers at that base, Camp Chapman.
CIA officers recruited Humam Khalil Abu Mulal al-Balawi, a Jordanian doctor and al-Qaeda propagandist, who they hoped would lead them to al-Zawahri. He provided US officials with information about al-Zawahri’s health, convincing them that his intelligence was real. But he was actually a double agent and on December 30, 2009, he showed up at Camp Chapman wearing a suicide vest. When it exploded, seven agents were killed.
For many, the Khost attack intensified efforts to find al-Zawahri. “To honor their legacy, you continue with the mission,” Mr. Hoffman said.
In 2012 and 2013, the CIA focused its hunt on Pakistan’s North Waziristan region. CIA analysts were confident they had found the small village where al-Zawahri was hiding. But intelligence agencies were unable to find his home in the town of about a dozen homes, making a raid or drone strike impossible.
However, the US manhunt forced al-Zawahri to remain in Pakistan’s tribal areas, possibly limiting the effectiveness of his leadership within al-Qaeda.
“Every time something related to bin Laden or Zawahri came up on the Intel channels, everyone stopped to step in and help,” said Lisa Maddox, a former CIA analyst. “It was the CIA’s promise to the public: to bring them to justice.”
On April 1, top intelligence officials briefed national security officials at the White House about the safe house and how they had tracked al-Zawahri. After the meeting, the CIA and other intelligence agencies worked to learn more about what they called al-Zawahri’s pattern of life.
One key idea was that he was never seen leaving the house and only seemed to get fresh air by standing on an upstairs balcony. He remained on the balcony for long periods, which gave the CIA a good opportunity to target him.
Al-Zawahri continued to work in the safe house, producing videos to be distributed to the al-Qaeda network.
A senior administration official, who spoke on condition of anonymity to discuss the sensitive decisions that led to the strike, said the information presented to the White House had been repeatedly vetted, including by a team of independent analysts tasked with identifying all those who remained in the safe house.
As options for a strike were developed, intelligence officials considered what kind of missile could be fired at al-Zawahri without causing much damage to the safe house or the neighborhood around it. They finally settled on a form of Hellfire missile designed to kill a single person.
William J. Burns, the CIA director, and other intelligence officials briefed President Biden on July 1, this time on the safe house model, the senior official said.
In that meeting, Mr. Biden asked about the possibility of collateral damage, prompting Burns to walk him through the steps of how the officers found al-Zawahri and corroborated his information and their plans to kill him.
Mr. Biden ordered a series of analyzes to try to predict the impact of the blow on the Taliban, the region and American efforts to move Afghans to the United States, the senior official said. The president also asked about the potential risks to Mark R. Frerichs, an American hostage held by the Haqqanis.
In June and July, officials met several times in the Situation Room to discuss the information and consider possible consequences.
The CIA’s plans called for it to use its own drones. Because it used its own assets, few Pentagon officials were included in the planning for the strike, and many senior military officials learned about it only shortly before the White House announcement, one official said.
On July 25, Mr. Biden, satisfied with the plan, authorized the CIA to carry out the airstrike when the opportunity presented itself. On Sunday morning in Kabul, he did. A drone flown by the CIA found al-Zawahri on his balcony. Agency officials fired the missile, ending a manhunt that lasted more than two decades.
Thomas Gibbons-Neff, Adam Goldman and Michael Crowley contributed to the report.