The origins of the war in Iraq have been linked back to the Sept. 11 terrorist attacks that killed 3,000 Americans in 2001. The Islamic militant group Al-Qaeda took credit for the attacks under its proclaimed holy war against the United States. The group is believed to have affiliates throughout the Middle East and Africa. Osama bin Laden was Al-Qaeda's top commander. The Sept. 11 attacks intensified U.S. surveillance of Al-Qaeda.