In his 2002 State of the Union address, the president outlined the danger from countries seeking weapons of mass destruction (WMDs) whether biological, chemical, or nuclear; he named three states as an "axis of evil" — North Korea, Iraq, and Iran. The Bush Doctrine took shape over the next several months. It stated that the United States had the right to preemptively use military force against nations that were a threat to us and were seeking WMDs. It became increasingly clear that the first target of preemption was to be Iraq. The administration argued that Iraq had biological and chemical weapons and was developing a nuclear program; there were possible links between Iraq's leader Saddam Hussein, September 11, and al Qaeda; overthrowing Hussein's regime and establishing a democratic Iraq could serve as a model for the entire region. In October 2002, Congress gave the president the authority to take military action against Iraq. While insisting on the return of weapons inspectors and threatening "serious action" for noncompliance, the United Nations Security Council refused to support a use of force resolution. The Unites States, along with Great Britain and a small contingent of troops from other nations, invaded Iraq in March 2003. Within a few months, Operation Iraqi Freedom captured Baghdad and other major cities, and Saddam Hussein's government was overthrown; Bush declared the end of major combat operations on May 1, 2003. But peace was to prove harder to win than the war.
Contrary to American expectations, Iraqis quickly saw coalition forces as occupiers rather than liberators. As the opposition grew, insurgent attacks became more deadly; car bombings, kidnappings, and "improvised explosive devices" (IEDs) took a high toll of civilian and military lives. The slow pace of reconstruction under the Coalition Provisional Authority, appointed by the United States to administer the country and incidents such as the mistreatment of detainees at Abu Ghraib prison, added to the problems. The Provisional Authority's decisions to disband the Iraqi army and abolish the Baath Party were likely counterproductive. The fact that no WMDs were found after the invasion and the recognition by the 9/11 Commission that Saddam Hussein did not have any connection with the attacks underminded the administration's justification for the war. Progress was also slow on the political front, but there were notable successes. An Iraqi Governing Council was in place by July 2003, and sovereignty was turned over to the interim government in June 2004. The country's first democratic election for the national assembly was held on January 30, 2005; a majority of the seats went to Shiites because many Sunnis boycotted the election. By the end of the year, voters approved a constitution with a federal system and elected members for parliament. Despite these positive developments, the insurgency intensified. Foreign fighters associated with al Qaeda in Iraq and growing sectarian violence between Shiites and Sunnis brought American casualties to over 3,000, while tens of thousands of Iraqis were killed. Many Americans were convinced that the administration had mismanaged the conflict and there were calls in and out of Congress to withdraw the troops.