On March 20, 2003, the Iraq war began when the United States military, along with troops from the United Kingdom, invaded the country of Iraq. Prior to the invasion, the governments of the United States and the United Kingdom believed there was a possibility of Iraq possessing weapons of mass destruction. Both nations believed there national security was threatened.

            In 2002, the United Nations Security Council passed a resolution calling for the officials in Iraq to cooperate with U.N. weapon inspectors to verify that it was not in possession of weapons of mass destruction and cruise missiles. The United Nations Monitoring, Verification and Inspection Commission was given access by Iraq under provisions of the U.N. resolution but found no evidence of weapons of mass destruction. Additional months of inspection to conclusively verify Iraq's compliance with the U.N. disarmament requirements were not undertaken. Iraq's declarations with regards to weapons of mass destruction could not be verified at the time, but unresolved tasks concerning Iraq's disarmament could be completed within months.

            The invasion of Iraq led to an occupation and the eventual capture of President Saddam Hussein, who was later tried in an Iraqi court of law and executed by the new Iraqi government. Violence against coalition forces and among various sectarian groups soon led to the Iraqi insurgency, strife between many Sunni and Shia Iraqi groups, and the emergence of a new faction of al-Qaeda in Iraq.

            In June 2008, U.S. Department of Defense officials claimed security and economic indicators began to show signs of improvement in what they hailed as significant and fragile gains. As public opinion favoring troop withdrawals increased and as Iraqi forces began to take responsibility for security, member nations of the coalition withdrew their forces. In late 2008, the U.S. and Iraqi governments approved a Status of Forces Agreement effective through January 1, 2012. This agreement establishes the rights and privileges of foreign personnel present in a host country in support of the larger security arrangement. The Iraqi Parliament also ratified a Strategic Framework Agreement with the U.S., aimed at ensuring cooperation in constitutional rights, threat deterrence, education, energy development, and other areas.

            In late February 2009, newly elected U.S. President Barack Obama announced an 18-month withdrawal window for combat forces, with approximately 50,000 troops remaining in the country to advise and train Iraqi security forces and to provide intelligence and surveillance. In a speech at the Oval Office on August 31, 2010 Obama declared that the American combat mission in Iraq has ended. Operation Iraqi Freedom is over, and the Iraqi people now have lead responsibility for the security of their country. Beginning September 1, 2010, the American operational name for its involvement in Iraq changed from Operation Iraqi Freedom to Operation New Dawn. The remaining 50,000 U.S. troops are now designated as advise and assist brigades assigned to non-combat operations while retaining the ability to revert to combat operations as necessary. According to the Associated Press, combat in Iraq is not over, and U.S. troops remain involved in combat operations alongside Iraqi forces, although U.S. officials say the American combat mission has formally ended.