It was an innocuous email, one of millions sent every day by spouses with updates on the situation at home. But this one was of particular interest to the National Security Agency, and contained clues that put the sender's husband in the cross hairs of a CIA drone.
Days later, Hassan Ghul — an associate of Osama bin Laden who provided a critical piece of intelligence that helped the CIA find the al-Qaida leader — was killed by a drone strike in Pakistan's tribal belt.
The U.S. government has never publicly acknowledged killing Ghul. But documents provided to the Washington Post by former NSA contractor Edward Snowden confirm his demise in October 2012 and reveal the agency's extensive involvement in the targeted killing program that has served as a centerpiece of President Barack Obama's counterterrorism strategy.
An al-Qaida operative who had a knack for surfacing at dramatic moments in the post-Sept. 11 story line, Ghul was an emissary to Iraq for the terrorist group at the height of that war. He was captured in 2004 and helped expose bin Laden's courier network before spending two years at a secret CIA prison. Then, in 2006, the United States delivered him to his native Pakistan, where he was released and returned to the al-Qaida fold.
But beyond filling in gaps about Ghul, the documents provide the most detailed account of the collaboration between the CIA and the NSA in the drone campaign.
The NSA is "focused on discovering and developing intelligence about valid foreign intelligence targets," an NSA spokeswoman said in a statement provided to the Washington Post on Wednesday, adding that the agency's operations "protect the nation and its interests from threats such as terrorism and the proliferation of weapons of mass destruction."
In the search for targets, the NSA has draped a surveillance blanket over dozens of square miles of northwest Pakistan. In Ghul's case, the agency deployed an arsenal of cyberespionage tools, secretly seizing control of laptops, siphoning audio files and other messages, and tracking radio transmissions to determine where Ghul might "bed down."
The email from Ghul's wife "about her current living conditions" contained enough detail to confirm the coordinates of that household, according to a document summarizing the mission. "This information enabled a capture/kill operation against an individual believed to be Hassan Ghul on October 1," it said.
The file is part of a collection of records in the Snowden trove that make clear that the drone campaign relies heavily on the NSA's ability to vacuum up enormous quantities of emails, phone calls and other fragments of signals intelligence.
To handle the expanding workload, the NSA created a secret unit known as the Counter-Terrorism Mission Aligned Cell to concentrate the agency's vast resources on hard-to-find terrorism targets. The unit spent a year tracking Ghul and his courier network, tunneling into an array of systems and devices, before he was killed. Without those penetrations, the document concluded, "this opportunity would not have been possible."