As Al Qaeda's operations chief, Abu Zubaydah was one of Usama bin Laden's top lieutenants and possibly the third-ranking figure in Al Qaeda.
Zubaydah was captured on March 28, 2002 — six months after the Sept. 11 terror attacks on New York and Washington, D.C. — during a joint U.S.-Pakistani raid on an Al Qaeda hideout in the industrial city of Faisalabad, during which he was shot and wounded.
He is believed to have masterminded the failed millennium bombing plots in Los Angeles and Jordan, and has been linked to failed plots on the U.S. embassies in Paris and Sarajevo.
Zubaydah, a Saudi-born Palestinian, is suspected of being an Al Qaeda financier said to be a link between bin Laden and many of Al Qaeda's operational cells.
The 38-year-old ran the Khalden camp in Afghanistan, where U.S. intelligence officials believe many of the Sept. 11 hijackers trained. Bin Laden's senior field commander is thought to have been Al Qaeda's chief coordinator of cells around the globe.
After the Sept. 11 attacks, Zubaydah led an effort to reorganize Al Qaeda in Pakistan. Financial transfers and intercepted communications suggested he was directing attempts to conduct new terrorist attacks against U.S. interests.
Zubaydah has been linked by intelligence and police officials to at least five Al Qaeda terrorist plots, including Sept. 11. In 2000, a Jordanian military court found him guilty in absentia of conspiracy to carry out terrorist attacks, and he was sentenced to death.
Vince Cannistraro, a former senior CIA counterterrorism chief, commenting after Zubaydah's capture, called him a "choke point" between bin Laden's will and actual terror attacks, adding that where bin Laden and deputy Ayman al-Zawahiri would set policy, Zubaydah would implement it.
U.S. officials after his capture said when the inner circle would order the bombing of an embassy, Zubaydah would select the embassy, cell and method of attack.
Intelligence officials said only bin Laden, Zawahiri and Mohammed Atef ranked higher than Zubaydah.
Despite his prominence, the FBI never named Zubaydah as a "most-wanted" terrorist.
After his capture, Zubaydah provided intelligence officials with leads to Ramzi bin al-Shibh, who also was captured in Pakistan. Bin al-Shibh was part of the Hamburg, Germany, cell of Al Qaeda where Sept. 11 hijacker Mohammed Atta was stationed.
The information from Zubaydah and bin al-Shibh led to the capture in the spring of 2003 of Khalid Sheik Mohammed, the confessed architect of the Sept. 11 attacks, according to U.S. officials.
Zubaydah also provided significant information on two operatives, including Jose Padilla, who planned to detonate a dirty bomb in the Washington, D.C., area, the officials noted.