"Iraq's chemical, biological, and nuclear weapons programs, together with Iraqi long-range missile development and support for terrorism, are the primary justifications put forward for military action. On March 17, 2003 President Bush issued an ultimatum demanding that Saddam Hussein and his sons depart from Iraq within 48 hours. On March 19, offensive operations began with air strikes against Iraqi leadership positions. By April 15, after 27 days of operations, coalition forces were in relative control of all major Iraqi cities. Iraqi political and military leadership had disintegrated. The major challenge to coalition forces is now the restoration of civil order and the provision of basic services to the urban population. As the U.S. ground offensive approached Baghdad, DOD civilian leadership came under criticism for not permitting the deployment of sufficient U.S. ground forces to maintain the offensive, protect lines of supply, and secure rear areas where sporadic Iraqi resistance continues. With the fall of Baghdad, Mosul, and Kirkuk, this criticism muted. There was no use of chemical or biological (CB) weapons, and no CB weapons stockpiles have been found, though two mobile labs believed to be biological agent production facilities have been discovered."
CRS Report for Congress, RL31701