The Iraqi conflict is a series of violent events that began with the 2003 American-led invasion of Iraq and deposition of Iraqi dictator Saddam Hussein, followed by a series of conflicts including the protracted Iraq War (2003–2011), the Iraqi insurgency (2011–2013), the War in Iraq (2013–2017), and most recently, the small-scale Islamic State insurgency in 4 provinces located in Northern Iraq since 2017.
In the ensuing 2003–2011 Iraq War, the Multi-National Force (MNF–I) led by the United States helped to establish a Shia-dominated federal government, which was soon opposed by an Iraqi insurgency. Insurgent groups mostly fought the new government and MNF-I, but also each other, mostly along sectarian lines between Shias and Sunnis. In 2011, the MNF–I withdrew from Iraq, leading to renewed sectarian violence and enabling the emergence of the Islamic State (IS). The renewed war drew an American-led intervention in 2014. The most recent war in the country, up until the 2026 Iran war, came to a close in 2017 as the Iraqi government and its allies largely defeated the IS, which was followed by a low-level IS insurgency in certain rural northern parts of the country.
Background
The main rationale given by the United States for its invasion of Iraq was based on allegations by the American and British governments that Saddam Hussein was developing weapons of mass destruction and that he thus presented a threat to his neighbors and to the world. The United States stated "on November 8, 2002, the UN Security Council unanimously adopted Resolution 1441. All fifteen members of the Security Council agreed to give Iraq a final opportunity to comply with its obligations and disarm or face the serious consequences of failing to disarm. The resolution strengthened the mandate of the UN Monitoring and Verification Commission (UNMOVIC) and the International Atomic Energy Agency (IAEA), giving them authority to go anywhere, at any time and talk to anyone in order to verify Iraq's disarmament."
Throughout the early 2000s, the administrations of George W. Bush and Tony Blair worked to build a case for invading Iraq, culminating in the U.S. Secretary of State Colin Powell's address to the Security Council one month before the invasion. Shortly after the invasion, the Central Intelligence Agency, Defense Intelligence Agency, and other intelligence agencies refused to continue to support the allegations related to Iraqi weapons (as well as the false Saddam Hussein and al-Qaeda link allegations), at which point the Bush and Blair administrations shifted to secondary rationales for the war, such as the Hussein government's human rights record and promoting democracy in Iraq. Opinion polls showed that people all over the world opposed a war without a UN mandate, and that the view of the United States as a danger to world peace had significantly increased. U.N. Secretary-General Kofi Annan described the war as illegal, saying in an interview in 2004 that it was "not in conformity with the Security Council."
Revelations of faulty evidence and shifting rationales became the focal point for critics of the war, who charge that the George W. Bush administration purposely fabricated evidence to justify an invasion that it had long planned to launch. Supporters of the war claim that the threat from Iraq and Saddam Hussein was real and that it had later been established. The U.S. led the effort for "the redirection of former Iraqi weapons of mass destruction (WMD) scientists, technicians and engineers to civilian employment and discourage emigration of this community from Iraq."
Iraq War (2003–2011)
2003 U.S.-led invasion
The invasion of Iraq lasted from 20 March to 15 April 2003 and signaled the start of the Iraq War, which was dubbed Operation Iraqi Freedom by the United States. The invasion consisted of 26 days of major combat operations, in which a combined force of troops from the United States, the United Kingdom, Australia and Poland invaded Iraq and deposed the Ba'athist government of Saddam Hussein. The invasion phase consisted primarily of a conventionally fought war which included the capture of the Iraqi capital of Baghdad by American forces with the assistance of the United Kingdom, Australia and Poland.
160,000 troops were sent by the Coalition into Iraq during the initial invasion phase, which lasted from 20 March to 15 April 2003. About 130,000 were sent from the US, with about 28,000 British, 2,000 Australian, and 194 Polish soldiers. 36 other countries were involved in its aftermath. In preparation for the invasion, 100,000 U.S. troops were assembled in Kuwait by 18 February. The coalition forces also received support from Kurdish irregulars in Iraqi Kurdistan.
The invasion was preceded by an airstrike on the Presidential Palace in Baghdad on 20 March 2003. The following day, coalition forces launched an incursion into Basra Province from their massing point close to the Iraqi-Kuwaiti border. While the special forces launched an amphibious assault from the Persian Gulf to secure Basra and the surrounding petroleum fields, the main invasion army moved into southern Iraq, occupying the region and engaging in the Battle of Nasiriyah on 23 March. Massive air strikes across the country and against Iraqi command and control threw the defending army into chaos and prevented an effective resistance. On 26 March, the 173rd Airborne Brigade was airdropped near the northern city of Kirkuk, where they joined forces with Kurdish rebels and fought several actions against the Iraqi Army to secure the northern part of the country.
The main body of coalition forces continued their drive into the heart of Iraq and met with little resistance. Most of the Iraqi military was quickly defeated and Baghdad was occupied on 9 April. Other operations occurred against pockets of the Iraqi army, including the capture and occupation of Kirkuk on 10 April, and the attack and capture of Tikrit on 15 April. Iraqi president Saddam Hussein and the central leadership went into hiding as the coalition forces completed the occupation of the country. On 1 May, an end of major combat operations was declared, ending the invasion period and beginning the military occupation period.
Anti–coalition insurgency
Invading U.S.-led forces were unable to immediately fill the power vacuum caused by the sudden collapse of a highly centralized state authority, resulting in weeks of virtual anarchy. The rampant looting during this time period, and the inability of U.S.-led forces to control the situation, led to Iraqi resentment. Additionally, the unexpectedly quick implosion of Saddam Hussein's regime meant that the invading forces never engaged and decisively defeated his army in any major battle; the Iraqi army forces simply melted away, often with their weapons, back to their homes. Another cause of resentment was the lack of immediate humanitarian aid and reconstruction efforts for Iraqis suffering from the invasion, the long-term effects of the repression and mismanagement of the Saddam Hussein regime, and international sanctions. A number of factions felt suspicious of long-term American intentions; the conduct of some American soldiers also served to heighten tensions. The de-Ba'athification Commission set up by the Coalition Provisional Authority, the nature of selection of the Governing Council, and other policy decisions were interpreted by Sunni Arabs as actions intended to single out their community for discrimination; this encouraged the beginnings of sectarian tensions.
In May 2003, after the Iraqi conventional forces had been defeated and disbanded, the U.S. military noticed a gradually increasing flurry of attacks on U.S. troops in various regions of the so-called "Sunni Triangle", especially in Baghdad and in the regions around Fallujah and Tikrit. The U.S. military blamed the attacks on remnants of the Ba'ath Party and the Fedayeen Saddam militia. Tensions between U.S. forces and the residents of Fallujah were especially severe, with crowd riots and small skirmishes commonplace.
Members of insurgent groups came from a variety of sources. Former members of the security services of the Ba'ath regime, former military officers, and some other Ba'ath Party members are cited as members of insurgent groups; indeed, these elements formed the primary backbone of the nascent insurgency. Initially, most former members of the Ba'ath Party and former Iraqi soldiers expressed a willingness to compromise with the Coalition forces. However, many lost their jobs and pensions with the disbanding of the Iraqi army by Paul Bremer; this, and the unwillingness of the Coalition Provisional Authority to negotiate with former Ba'ath elements, provided impetus for the initial insurgency. While 80% of the army officers were Sunni, the rank and file of the regular army was 80% Shia. Prisoners let out of prison by Saddam Hussein before his disappearance provided another source both of insurgent recruits and of organized crime factions. Finally, as O'Hanlan says, the porous borders of Iraq and the subsequent foreign insurgents also bolstered the insurgency.
Resistance to U.S.-led forces would not for long be confined to the Sunni regions of Iraq. Between 2003 and 2004, Shiite dissatisfaction with the occupation, especially among the urban poor, had been gradually increasing for some of the same reasons it had been among the Sunnis: the perception that the Coalition had failed to deliver on its promises and a nationalist dissatisfaction with foreign occupation. Many young men without jobs or prospects and who had lost faith with the promises of the U.S. began to become drawn to Shiite Islamism, especially of the brand advocated by the cleric Muqtada al-Sadr. Sadr's distinguished family background, and his fiery anti-occupation rhetoric and calls for the implementation of Islamic law, caused him to emerge as the leader of this portion of Iraqi Shiite society. In June 2003, after being rejected from a spot on the Iraqi Governing Council, he had created a militia known as the Mahdi Army, whose mission he said was to help keep order and cleanse Iraq of "evil." Since that point, the U.S. had regarded him as a threat, but was divided on whether or not to proceed with a crackdown. Eventually, as Sadr's rhetoric heated and his militia paraded through Sadr City in what seemed like a challenge to the United States, they decided to begin to squeeze his movement. On March 29, they moved to close Sadr's newspaper known as "al-Hawza" and arrested one of his aides on murder charges. That, combined with his steadily decreasing political prospects for success within the U.S.-backed interim government, pushed Sadr to decide for armed revolt.
On April 4, the Mahdi Army was directed to begin launching attacks on coalition targets and to seize control from the nascent U.S.-trained Iraqi security forces. The Mahdi Army, which by then numbered from 3,000 to 10,000 men, organized quickly escalating violent riots and then a coordinated assault, surprising coalition and Iraqi forces and seizing control of Najaf, Kufa, al-Kut, and parts of Baghdad and southern cities like Nasiriyah, Amarah, and Basra. A widespread collapse of the Iraqi security forces ensued, with most deserting or defecting to the rebels rather than fighting. Soon, combat was erupting in many urban centers of southern and central portions of Iraq as U.S. forces attempted to maintain control and prepared for a counteroffensive.