Operation Inherent Resolve (OIR) is the United States military's operational name for the international war against the Islamic State, including both a campaign in Iraq and a campaign in Syria, with a closely related campaign in Libya. Through 18 September 2018, the U.S. Army's III Armored Corps was responsible for Combined Joint Task Force – Operation Inherent Resolve (CJTF—OIR) and were replaced by the XVIII Airborne Corps. The campaign is primarily waged by American and British forces in support of local allies, most prominently the Iraqi security forces and Syrian Democratic Forces (SDF). Combat ground troops, mostly special forces, infantry, and artillery have also been deployed, especially in Iraq. Of the airstrikes, 70% have been conducted by the military of the United States, 20% by the United Kingdom and the remaining 10% being carried out by France, Turkey, Canada, the Netherlands, Denmark, Belgium, Saudi Arabia, the United Arab Emirates, Australia and Jordan.

The Islamic State (IS), also known as the Islamic State of Iraq and the Levant (ISIL), the Islamic State of Iraq and Syria (ISIS) and by its Arabic acronym Daesh, is a transnational Salafi jihadist group and a former unrecognised quasi-state. Its origins were in the Jai'sh al-Taifa al-Mansurah organization founded by Abu Omar al-Baghdadi in 2004, which fought alongside al-Qaeda during the Iraqi insurgency. The group gained global prominence in 2014, when its militants successfully captured large territories in northwestern Iraq and eastern Syria, taking advantage of the ongoing Syrian civil war. By the end of 2015, it ruled an area with an estimated population of twelve million people, where it enforced its extremist interpretation of Islamic law, managed an annual budget exceeding US$1 billion, and commanded more than 30,000 fighters.