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.

• Just and necessary war viewpoint - Holds that removing Saddam Hussein was a justified act of preventive security and humanitarian liberation, regardless of the WMD intelligence failure, and that the war removed a destabilizing dictator and created an opportunity for Iraqi self-governance. iraq-war-necessary-war-viewpoint
• Illegal or unjustified war viewpoint - Holds that the invasion lacked clear United Nations Security Council authorization and violated international law, and that it was launched on a flawed or manipulated factual basis. iraq-war-illegal-war-viewpoint
• Strategic blunder viewpoint - Holds that regardless of legality or initial intent, the war was a serious miscalculation that destabilized the region, weakened U.S. strategic position, and produced costs disproportionate to any benefit. iraq-war-strategic-blunder-viewpoint
• Geopolitical or economic motive viewpoint - Holds that stated justifications (WMD, terrorism, human rights) were secondary to underlying motives such as control of oil resources, regional military positioning, or completion of unfinished business from the Gulf War. iraq-war-geopolitical-motive-viewpoint
• Iraqi self-determination viewpoint - Centers Iraqi voices and experiences, holding that the war's legitimacy should be assessed primarily by its effects on Iraqi sovereignty, civilian welfare, and political agency rather than by the strategic interests of intervening powers. iraq-war-self-determination-viewpoint

• The Bush administration's use of prewar intelligence, including the claim of Iraqi attempts to acquire uranium and the broader case presented to the UN Security Council, remains disputed regarding the degree of deliberate misrepresentation versus genuine error. iraq-war-prewar-intelligence-controversy
• The conduct of U.S. and coalition forces and contractors, including detainee treatment at Abu Ghraib prison, generated sustained legal and political controversy. iraq-war-abu-ghraib-controversy
• The decision to disband the Iraqi Army and pursue de-Ba'athification under the Coalition Provisional Authority is disputed as a contributing cause of the subsequent insurgency. iraq-war-debaathification-controversy

• History: iraq-war-history
• Debate: iraq-war-casualty-figures-debate
• Debate: iraq-war-legality-debate
• Viewpoint Debate: iraq-war-necessary-war-illegal-war-viewpoint-debate
• Consensus: iraq-war-wmd-intelligence-consensus
• Controversy: iraq-war-abu-ghraib-controversy
• Related Main Topic: September 11th Attacks
• Related Main Topic: United States of America - 21st Century History
• Related Main Topic: United States of America - History
• Related Main Topic: War On Terror

1. U.S. Senate Select Committee on Intelligence, *Report on the U.S. Intelligence Community's Prewar Intelligence Assessments on Iraq* (Washington, DC: U.S. Government Printing Office, 2004).
2. The Iraq Inquiry [Chilcot Report], *Report of the Iraq Inquiry* (London: House of Commons, 2016).
3. Iraq Survey Group, *Comprehensive Report of the Special Advisor to the Director of Central Intelligence on Iraq's WMD* (Washington, DC: Central Intelligence Agency, 2004).
4. Burnham, Gilbert, Riyadh Lafta, Shannon Doocy, and Les Roberts. “Mortality after the 2003 Invasion of Iraq: A Cross-Sectional Cluster Sample Survey.” *The Lancet* 368, no. 9545 (2006): 1421-1428.
5. Iraq Body Count, *Iraq Body Count Database* (London: Iraq Body Count, ongoing).
6. Ricks, Thomas E. *Fiasco: The American Military Adventure in Iraq*. New York: Penguin Press, 2006.