On 15 June 2014, United States President Barack Obama ordered United States forces to be dispatched in response to the Northern Iraq offensive (June 2014) of the Islamic State (ISIL), as part of Operation Inherent Resolve. At the invitation of the Iraqi government, American troops went to assess Iraqi forces and the threat posed by ISIL.

In early August 2014, ISIL began its Northern Iraq offensive. On 5 August, the United States started supplying the Kurdish Peshmerga forces with weapons. On 8 August, the United States began airstrikes against ISIL positions in Iraq. Nine other countries also launched airstrikes against ISIL, more or less in concert with Kurdish and Iraqi government ground troops. By December 2017, ISIL had no remaining territory in Iraq, following the 2017 Western Iraq campaign.

In addition to direct military intervention, the American-led coalition provided extensive support to the Iraqi Security Forces (ISF) via training, intelligence, and personnel. The total cost of coalition support to the ISF, excluding direct military operations, was officially announced at ~$3.5 billion by March 2019.CJTF-OIR Official Twitter. 20 March 2019. Accessed 25 March 2019. 189,000 Iraqi soldiers and police officers received training from coalition forces.CJTF-OIR Official Twitter. 15 March 2019. Accessed 25 March 2019.

Despite U.S. objections, the Iraqi parliament demanded U.S. troops to withdraw in January 2020 following the deaths of Iraqi Deputy chief of the Popular Mobilization Units and popular Iranian Quds leader Qasem Soleimeni in a U.S. airstrike. It was also announced that both the U.K and Germany were cutting the size of troops in Iraq as well, In addition to withdrawing some of its troops, the U.K. pledged to completely withdraw from Iraq if asked to do so by the Iraqi government and Germany "temporarily thinned out" its bases in Baghdad and Camp Taji. Canada later joined in with the coalition withdrawal as well by transferring some of its troops stationed in Iraq to Kuwait. French and Australian forces stationed in the country have also objected to a withdrawal as well. The United Nations estimated in August 2020 that over 10,000 ISIL fighters remained in Iraq and Syria.

The coalition officially concluded its combat mission in Iraq in December 2021, but U.S. troops remained in Iraq to advise, train, and assist ISF against the ongoing ISIL insurgency, including providing air support and military aid. Under an agreement concluded in September 2024, the last U.S. troops departed Iraq on September 30, 2026.The US military says its withdrawal of troops from Iraq is complete The Iraqi government declared a 4-day holiday through October 3, designating September 30 as Sovereignty Day. Iraq Announces Four-Day Holiday for Sovereignty Day

Background Previous U.S. involvement In 2003, the United States led a controversial invasion of Iraq, which was based on flawed intelligence that Iraq had weapons of mass destruction and links to al-Qaeda while under Ba'athist rule. By 2007, the number of U.S. forces in Iraq peaked at 170,000 soldiers. In 2011, the U.S. had withdrawn most of its troops from Iraq and later kept 20,000 employees in its embassy and consulates, including dozens of U.S. Marine Embassy Guards and approximately 4,500 private military contractors. Following the withdrawal, the U.S. resumed flying surveillance aircraft in order to collect intelligence about insurgent Islamist fighters targeting the Iraqi government.

Old enemies After the invasion, the previous incarnations of ISIL (Jama'at al-Tawhid wal-Jihad [Jama'at], the Mujahideen Shura Council [MSC], and al-Qaeda in Iraq) interfered with occupation by the U.S.-led coalition. Jama'at and MSC started a campaign of terrorism in response to what resistance commander Abu Mohammed described as an occupation intended to humiliate and enchain the people of Iraq. Attacks by Jama'at and MSC targeted hundreds of Muslim Iraqis, several U.S. soldiers, and included in 2010 a church full of Christians. These attacks are presumed to include the beheadings in 2004 of three American civilians, one British, one South Korean, and one Japanese civilian.

ISIL advances in Northern Iraq

After the December 2011 withdrawal of U.S. troops from Iraq, violent insurgency of mainly Sunni Islamic Islamist fighters targeting the Iraqi government continued in what is called the Iraqi insurgency.

Between 5 and 11 June 2014, Sunni Islamic, jihadist, 'Islamic State of Iraq and the Levant' (ISIL) militants, already successful in the Syrian civil war, conquered the Iraqi cities of Samarra, Mosul and Tikrit, and threatened the Mosul Dam and Kirkuk, where Iraqi Kurdish Peshmerga troops took control from the Iraqi government.

Internet beheading video campaign 2014–2015

On 12 August 2014, ISIL started a campaign of beheading Western and Japanese civilian hostages (announced 12 August, James Foley 19 August, Steven Sotloff 2 September, David Haines 13 September, Hervé Gourdel 24 September, Alan Henning 3 October, Peter Kassig 16 November, Haruna Yukawa sometime January 2015, Kenji Goto 30 January 2015) marketed via the internet.

U.S.-led coalition against ISIL

On 5 September, 15 September and 3 December 2014, different sets of countries came together to discuss concerted action against ISIL. Present at all three meetings were the United States, United Kingdom, France, Germany, Italy, Canada, Turkey, and Denmark.

The coalition of 5 September (10 countries) decided to support anti-ISIL forces in Iraq and Syria.'U.S. Forms Anti-ISIS Coalition at NATO Summit' . Time, 5 September 2014. Retrieved 14 June 2015.

The coalition of 15 September (26 countries) decided to support the Iraqi government militarily."International Conference on Peace and Security in Iraq (Paris, September 15, 2014)" . France Diplomatie (undated). Retrieved 14 June 2015.

The coalition of 3 December 2014 (59 countries) agreed on a many-sided strategy, including cutting off ISIL's financing and funding and exposing ISIL's true nature.'Joint Statement Issued by Partners at the Counter-ISIL Coalition Ministerial Meeting'. United States Department of State, 3 December 2014. Retrieved 16 June 2015.

U.S. naming controversy

Unlike previous U.S. combat operations, no name was initially given to the 2014 military operation in Iraq and Syria by the U.S. government, until mid-October. The fact that the operation was still nameless drew considerable media criticism. U.S. soldiers remained ineligible for Campaign Medals and other service decorations due to the continuing ambiguous nature of the U.S. involvement in Iraq. On 15 October 2014, two months after the first airstrikes by the U.S., the operation was named Inherent Resolve.

Support of the Iraqi government After the United States in June 2014 started to send troops to Iraq to secure American interests and assets and advise the Iraqi forces (see section U.S. surveillance and military advising in Iraq), President Barack Obama end of September planned to send 1,600 troops to Iraq as "advisers" to the Iraqi Army and Kurdish forces. 800 of them would provide security for soldiers and Marines and for property; hundreds would train and advise Iraqi and Kurdish forces how to fight ISIL. 8–9 November Obama doubled the number of American soldiers in Iraq to some 3,100.Obama doubling US troop levels in Iraq. Stars and Stripes, 7 November 2014. Retrieved 18 December 2014.NRC Handelsblad, 11 November 2014. By February 2015, the U.S. had deployed 4,500 troops. In June 2015, the U.S. had deployed an additional 450 troops to Iraq, increasing the U.S. troop presence in Iraq to at least 4,850.

Canadian Prime Minister Harper announced on 4 September 2014 that Canada would deploy "about 100" military advisers to be based in Baghdad assisting the Iraqi Military in the fight against ISIL. These personnel are special operations forces which would work closely with U.S. special forces to "provide advice that will help the government of Iraq and its security forces be more effective against ISIL", but their role was not expected to be direct combat. CBC News reports that about 100 Canadians would be deployed, primarily to help Kurdish forces.

Portugal has worked with neighboring Spain to provide training to the Iraqi Army south of Baghdad.

Building Partner Capacity

The Building Partner Capacity (BPC) program is meant to help the Iraqi government to prepare forces for the counter-attack against ISIL and the regaining of its territory.'Australia to contribute to the Building Partner Capacity mission in Iraq' . Australian government, 14 April 2015. Retrieved 19 August 2015. Australia in April 2015 committed 300 military personnel to the BPC training mission in Iraq. According to the U.S. Department of Defense, by May 2015 a dozen countries had committed themselves to the BPC program: Australia, Belgium, Denmark, France, Germany, Italy, Netherlands, New Zealand, Norway, Spain, United Kingdom and United States.'Counter-ISIL military coalition concludes operational planning conference' . U.S. Central Command News Release, 1 May 2015. Retrieved 19 August 2015.

Denmark sent 120 military personnel to Iraq in November 2014 to train the Iraqi Army. Germany began shipping non-lethal military equipment to the Iraqi government and the Kurdish Region early in the intervention. Italy offered to supply weapons, ammunition, and other aid to local forces in Iraq. The prime minister of Italy Matteo Renzi visited Iraq and the Kurds on 20 August 2014 to consider the response to ISIL. He said that without international involvement it would be a "new Srebrenica". New Zealand announced in November 2014 it would send up to 143 military personnel to help train local Iraqi security forces. 16 of which were to be trainers, the remaining personnel will be deployed to protect the trainers, and help with advisory/intelligence roles. New Zealand also sent up to $14.5m in humanitarian aid. Norway sent 5 headquarters personnel and 120 advisors in October 2014 to help train the Iraqi Army, and has used transport aircraft to deliver supplies to Iraq.'Norway to send 120 soldiers to Iraq to help train army'. Al Arabiya News, 30 October 2014. Retrieved 9 March 2015. Spain provided 300 instructors to train the Iraqi Army and offered to provide weapons to both the Iraqi Army and the Kurdish Peshmerga forces; Spain also stationed a Patriot missile battery and 150 servicemen in Turkey in case of cross-border attacks against its NATO ally.

By May 2015, the program had trained 6,500 Iraqi forces.

Military aid to the Kurds

Spokesman Halgurd Hikmat for the Peshmerga Ministry confirmed that the United States, the United Kingdom, Germany, France, Canada, Italy, and also Finland have agreed to supply weapons and military goods to Kurdish Peshmerga. Erbil-based BASNEWS reported that the Kurdistan Regional Government, in cooperation with the Iraqi and American governments, will open a military air base in Erbil.

On 5 October 2015, CJTF-OIR announced that it had given 50,000 rifles and machine guns, 56 million rounds of small arms ammunition, 677+ mortars, 73,000+ mortar rounds, 5,000+ anti-tank weapons, 56,000+ anti-tank rounds, and 150+ vehicles to the Iraqi Kurdish forces.Operation Inherent Resolve's official Facebook page, U.S. Department of Defense, facebook.com, 5 October 2015 The United States had begun on 5 August 2014, with the direct supply of munitions to the Iraqi Kurdish Peshmerga forces and, with Iraq's agreement, the shipment of Foreign Military Sales (FMS) program weapons to the Kurds, according to Zalmay Khalilzad, the former U.S. ambassador to Iraq and the U.N., in The Washington Post, and the following days the American CIA secretly sent arms to the Kurds. Before 11 August, U.S. and allies had started rushing antitank weapons etc. to Kurdish fighters, and the U.S. intended to provide longer-range weapons.