Al Qaeda leader Ayman al-Zawahiri was killed in a US strike in Afghanistan over the weekend, the biggest blow to the militant group since its founder Osama bin Laden was killed in 2011.

Zawahiri had been in hiding for years and the operation to locate and kill him was the result of “careful patient and persistent” work by the counter-terrorism and intelligence community, a senior US administration official told reporters.

Speaking on the condition of anonymity, the official provided the following details on the operation:

For several years, the US government had been aware of a network that it assessed supported Zawahiri, and over the past year, following the United States’ withdrawal from Afghanistan, officials had been watching for indications of Al Qaeda’s presence in the country.

This year, officials identified that Zawahiri’s family — his wife, his daughter and her children — had relocated to a safe house in Kabul and subsequently identified Zawahiri at the same location.

Over several months, intelligence officials grew more confident that they had correctly identified Zawahiri at the Kabul safe house and in early April started briefing senior administration officials. National Security Adviser Jake Sullivan subsequently briefed President Joe Biden.

“We were able to build a pattern of life through multiple independent sources of information to inform the operation,” the official said.

Once Zawahiri arrived at the Kabul safe house, officials were not aware of him leaving it and they identified him on its balcony — where he was ultimately struck — on multiple occasions, the official said.

Officials investigated the construction and nature of the safe house and scrutinised its occupants to ensure the United States could confidently conduct an operation to kill Zawahiri without threatening the structural integrity of the building and minimising the risk to civilians and Zawahiri’s family, the official said.

In recent weeks, the president convened meetings with key advisers and cabinet members to scrutinise the intelligence and evaluate the best course of action. On July 1, Biden was briefed on a proposed operation in the White House Situation Room by members of his cabinet including CIA Director William Burns

Biden “asked detailed questions about what we knew and how we knew it” and closely examined a model of the safe house the intelligence community had built and brought to the meeting.

He asked about lighting, weather, construction materials, and other factors that could affect the success of the operation, the official said. The president also requested an analysis of the potential ramifications of a strike in Kabul.

A tight circle of senior inter-agency lawyers examined the intelligence reporting and confirmed that Zawahiri was a lawful target based on his continuing leadership of Al Qaeda.

On July 25, the president convened his key cabinet members and advisers to receive a final briefing and discuss how killing Zawahiri would affect America’s relationship with the Taliban, among other issues, the official said. After soliciting views from others in the room, Biden authorised “a precise tailored air strike” on the condition that it minimises the risk of civilian casualties.

The strike was ultimately carried out at 9:48pm ET on July 30 by a drone firing so-called “hellfire” missiles.

Top security

Zawahiri was moved to a “very safe place” in Kabul a few months after the Taliban took control of Afghanistan in August last year, a senior leader of the group told Reuters on Tuesday on the condition of anonymity.

Sherpoor is a quiet, leafy part of Kabul with large houses, where former Afghan general and ethnic Uzbek strongman Abdul Rashid Dostum had lived, among other local dignitaries. Some houses have swimming pools in their attached gardens.

A woman who lives in the neighbourhood and spoke to Reuters on condition of anonymity said she and her family of nine moved to the safe room of their house when she heard an explosion at the weekend. When she later went to the rooftop, she saw no commotion or chaos and assumed it was some rocket or bomb attack — which is not uncommon in Kabul.

Taliban sources said the group gave the “highest-level security” to Zawahiri in Kabul but he was largely inactive operationally and needed the Taliban’s permission to move.

A Kabul police official described Sherpoor as Kabul’s “most safe and secure neighbourhood” and that the drone strike there was a “great shock”.

He said influential people from the former governments of Hamid Karzai and Ashraf Ghani had built spacious houses in Sherpoor. Senior Taliban leaders and their families now lived there, the official said.