Born in Saudi Arabia, Abu Zubaydah has been close to al-Qaida since the group’s early years, helping to operate a popular terrorist training camp near the border between Afghanistan and Pakistan in the early 1990s. He became an associate of Ibn al-Shaykh al-Libi, and served as a chief recruiter for al-Qaida.

According to a BBC news profile of Zubaydah, before his capture “few photographs of him were in existence, [and] he had used at least 37 aliases and was considered a master of disguise.”

In the late 1990s, Abu Zubaydah played a lead role in one of the 2000 millennium attack plots, and a possible tangential role in a second. There were plans to bomb a fully booked Radisson hotel in Amman, Jordan, and three other sites. This targeted tourists from the United States and Israel. But on November 30, 1999, Jordanian intelligence intercepted a call between Abu Zubaydah and Khadr Abu Hoshar, a Palestinian militant, and determined that an attack was imminent. Jordanian police arrested 22 conspirators and foiled the attack. Abu Zubaydah was sentenced to death in absentia by a Jordanian court for his role. There is also evidence that Abu Zubaydah approved the Los Angeles airport bomb plot in 2000. This plot was also foiled.

In March of 2001, Condoleezza Rice was informed by the CIA that Zubaydah was planning a major operation in the near future. This was one of the first of many reports in the Spring of 2001 that increased the threat level and indicated that an attack was coming. Many of these reports mentioned Zubaydah by name. The attack finally came in the form of the September 11, 2001 attacks.

The U.S. government believes he became al-Qaeda’s top military strategist following the death of Muhammad Atef in November 2001. A later plot to bomb the U.S. embassy in Paris failed.

American intelligence officials alleged, in October 2001, that six Arab men, living in Bosnia, had been plotting to bomb the U.S. Embassy in Sarajevo, because they believed one of these men had made calls to a phone number in Afghanistan that had once been used by Zubaydah. These six men, dubbed the Algerian Six, were kidnapped following their acquittal by the Bosnian Supreme Court, and ended up in Guantanamo. American intelligence officials quietly dropped the allegation that there had been a plot to bomb the embassy from the factors favoring their continued detention.

Middle East sources have told the Associated Press Abu Zubaydah developed a unique talent in mortars and other heavy weaponry that attracted the attention of bin Laden. He was apparently named bin Laden’s second deputy in 1995, responsible for screening recruits and devising terrorist plans. Where bin Laden and deputy Ayman al-Zawahri would set policy, Abu Zubaydah would implement it. U.S. officials said when the inner circle would order the bombing of an embassy, Abu Zubaydah would select the embassy, cell and method of attack. Ahmed Ressam, convicted April 2001 of smuggling, terrorist conspiracy and other charges in the Los Angeles millennium plot, described Abu Zubaydah’s role as a recruiter during court testimony. “He is the person in charge of the camps. He receives young men from all countries. He accepts you or rejects you. And he takes care of the expenses for the camps. He makes arrangements for you when you travel coming in or leaving,” Ressam said. Prospective recruits in Pakistan would meet Abu Zubaydah, who would assign them to camps. When they finished training, he placed them in cells overseas. Zubaydah is also believed to have been a field commander for the October 2000 bombing of the USS Cole in Yemen, in which 17 U.S. sailors were killed, and intelligence and police officials have linked him to at least five al Qaeda plots. Middle East sources said Abu Zubaydah helped set up the terrorist cell in Jordan charged with carrying out the millennium plot to attack American and Israeli targets.