Occupation of Iraq (2003–2011)

The occupation of Iraq (2003–2011) began on 20 March 2003, when the United States invaded with a military coalition to overthrow Iraqi president Saddam Hussein and his Arab Socialist Ba'ath Party, and continued until 18 December 2011, when the final batch of American troops left the country. While the United States, the United Kingdom, and Australia were the largest contributors to the coalition, 29 other countries, such as Japan, were involved in the Iraq War in a lesser capacity. Additionally, several private military contractors took part in enforcing the occupation.

It was a period of violence and political turmoil, and saw strong foreign influence exerted on Iraqi politics. In April 2003, the fall of Saddam's government was formally marked by the establishment of the Coalition Provisional Authority, which later appointed and granted limited powers to the Iraq Interim Governing Council. In June 2004, the Iraqi Interim Government was established, ending the international armed conflict that had existed between Iraq (that is, Ba'athist Iraq) and the United States. Following the January 2005 Iraqi parliamentary election, this administration was replaced by the Iraqi Transitional Government. A year later, the Al Maliki I Government took office.

Efforts to rebuild post-Saddam Iraq were slowed when the American-led military coalition and the new Iraqi government became locked in a grueling conflict with a stronger-than-expected militant Iraqi insurgency, leading to difficult living conditions for the country's population throughout the period.

A military occupation was established and run by the Coalition Provisional Authority (CPA), which later appointed and granted limited powers to an Iraq Interim Governing Council. Troops for the invasion came primarily from the United States, the United Kingdom, and Australia, but 29 other nations also provided some troops, and there were varying levels of assistance from Japan and other allied countries. Tens of thousands of private security personnel provided protection of infrastructure, facilities and personnel.

Coalition and allied Iraqi forces fought a stronger-than-expected militant Iraqi insurgency, and so the reconstruction of Iraq was slow. In mid-2004, the direct rule of the CPA was ended and a new "sovereign and independent" Interim Government of Iraq assumed the full responsibility and authority of the state. The CPA and the Governing Council were disbanded on 28 June 2004, and a new transitional constitution came into effect.

Sovereignty was transferred to a Governing Council Iraqi interim government led by Iyad Allawi as Iraq's first post-Saddam prime minister; this government was not allowed to make new laws without the approval of the CPA. The Iraqi Interim Government was replaced as a result of the elections which took place in January 2005. A period of negotiations by the elected Iraqi National Assembly followed, which culminated on 6 April 2005 with the selection of, among others, Prime Minister Ibrahim al-Jaafari and President Jalal Talabani. Prime Minister al-Jaafari led the majority party of the United Iraqi Alliance (UIA), a coalition of the al-Dawa and SCIRI (Supreme Council for the Islamic Revolution in Iraq) parties. Both parties are backed by Tehran, and were banned by Saddam Hussein.

An international armed conflict (IAC) between the United States and Iraq in the Iraq War began when the US-led Coalition invaded Iraq on 19 March 2003. IAC continued after the invasion when the Coalition Provisional Authority (CPA) was established on 21 April to temporarily administer the domestic affairs of Iraq. Therefore, hostilities during the invasion and occupation of Iraq fell under the laws of war applicable to IAC, including the 1949 Geneva Conventions, to which the US and Iraq are parties to, and the 1907 Hague Convention IV - The Laws and Customs of War on Land, which is commonly accepted as customary international humanitarian law binding on non-signatories engaged in an IAC. According to Article 42 under Section III of the Hague Convention IV - The Laws and Customs of War on Land, "[t]erritory is considered occupied when it is actually placed under the authority of the hostile army."

There may be situations where the former occupier will maintain a military presence in the country, with the agreement of the legitimate government under a security arrangement (e.g., US military presence in Japan and Germany). The legality of such agreement and the legitimacy of the national authorities signing it are subject to international recognition, whereby members of the international community re-establish diplomatic and political relations with the national government.