"U.S. mistakes in the invasion of Iraq led to the current insurgency and sectarian fighting, former U.S. Secretary of State Colin Powell says. "We made some serious mistakes in the immediate aftermath of the fall of Baghdad," Powell told the National School Board Association's annual conference in Chicago. "We didn't have enough troops on the ground. We didn't impose our will. And as a result, an insurgency got started, and ... it got out of control.""