The Iraq War was an armed conflict that began on 20 March 2003 with the invasion of Iraq by a United States-led multinational coalition and continued through varying phases of occupation, insurgency, and civil conflict until the withdrawal of U.S. combat forces in December 2011. The war's name and periodization are themselves contested: some analysts and sources treat the 2003-2011 U.S. military presence as a discrete conflict, while others extend “Iraq War” to include the subsequent rise of the Islamic State and the 2014-2017 campaign against it. This article uses the 2003-2011 period as its primary scope and links related phases below. See iraq-war-naming-periodization-debate for differing views on scope.
The invasion was launched by the United States, United Kingdom, and a coalition of other states, citing Iraqi President Saddam Hussein's alleged possession of weapons of mass destruction (WMD), alleged ties to terrorist organizations, and human rights violations under his government. The invasion led to the rapid collapse of the Ba'athist government and the capture of Saddam Hussein, followed by a multi-year occupation administered initially by the Coalition Provisional Authority. The occupation period saw the rise of a Sunni insurgency, sectarian violence between Sunni and Shia militias, and the emergence of al-Qaeda in Iraq. A U.S. troop increase known as “the surge” began in 2007. Combat operations formally ended in 2010, and the last U.S. troops withdrew in December 2011. Estimates of total deaths, including civilians, combatants, and those who died from war-related causes, vary widely by source and methodology, ranging from roughly 150,000 to over 600,000, depending on the study and timeframe used.
For background on Iraq's modern political history prior to 2003, see iraq-war-history.
Subsequent investigations by U.S., U.K., and other governmental bodies found that Iraq did not possess the stockpiles of chemical, biological, or nuclear weapons alleged before the invasion, and that prewar intelligence assessments overstated the certainty of Iraqi WMD programs. Disagreement persists over whether this resulted from intelligence failure, politicization of intelligence, or both, and over the broader strategic and humanitarian consequences of the war, including its role in regional instability and the rise of the Islamic State. Casualty figures, the war's relationship to subsequent Iraqi sectarian conflict, and its long-term effect on U.S. foreign policy and credibility remain actively debated among historians, political scientists, and policymakers.
There is broad consensus, corroborated by independent academic and arms-control researchers in addition to governmental inquiries-including the U.S. Senate Select Committee on Intelligence, the U.K.'s Iraq Inquiry (Chilcot Report), and the Iraq Survey Group-that Iraq did not possess operational stockpiles of weapons of mass destruction at the time of the 2003 invasion, and that key prewar intelligence assessments were inaccurate. See iraq-war-wmd-intelligence-consensus. No comparable consensus exists regarding whether the war was strategically justified, legally justified, or beneficial on net to U.S. or Iraqi interests; these remain matters of viewpoint and debate.