Many states began to intervene against the Islamic State (IS), in both the Syrian civil war and the War in Iraq (2013–2017), in response to its rapid territorial gains from its 2014 invasion of Iraq, widely condemned executions, human rights abuses and the fear of further spillovers of the Syrian civil war. In later years, there were also minor interventions by some states against IS-affiliated groups in Nigeria and Libya. All these efforts significantly degraded the Islamic State's capabilities by around 2019–2020. While moderate fighting continues in Syria, as of 2026, IS has been contained to a small area and force capability.
In mid-June 2014, Iran, according to American and British information, started flying drones over Iraq, and Iranian soldiers were in Iraq fighting IS. Simultaneously, the US ordered a small number of troops to Iraq and started flying crewed aircraft over Iraq. In July 2014, Iran sent Sukhoi Su-25 aircraft to Iraq, and Hezbollah purportedly sent trainers and advisers to Iraq in order to help Shia militias to monitor IS's movements. In August 2014, the US and Iran separately began a campaign of airstrikes on IS targets in Iraq. Since then, fourteen countries in a US-led coalition have also executed airstrikes on IS in Iraq and in Syria. Starting from September 2014, the US began closely co-operating with Saudi Arabia and Jordan to wage a co-ordinated aerial bombing campaign against IS targets across Iraq and Syria.
In September 2015, Russian forces launched their military intervention in Syria to support their ally, Bashar al-Assad, in the fight against the Islamic State. Although Moscow officially portrayed its intervention as an anti-IS campaign and publicly declared support for the "patriotic Syrian opposition", the vast majority of its bombings were focused on destroying bases of the Syrian opposition militias of the Free Syrian Army (FSA) and Southern Front. On the other hand, the United States and its Western allies have been opposed to the former Ba'athist regime for its purported state-sponsorship of terrorism, violent repression of the Syrian revolution and extensive use of chemical weapons. The US-led coalition trained, equipped and supported secular Free Syrian and Kurdish militias opposed to the Assad government during its anti-IS campaign. In the months following the beginning of both air campaigns, IS began to lose ground in both Iraq and Syria. Civilian deaths from airstrikes began to mount in 2015 and 2016. In mid-2016, the US and Russia planned to begin coordinating their airstrikes; however, this coordination did not materialize.
As of December 2017, IS was estimated to control no territory in Iraq, and 5% of Syrian territory, after prolonged actions. On 9 December 2017, Iraq declared victory in the fight against ISIL and stated that the War in Iraq was over. On 23 March 2019, IS was defeated territorially in Syria after losing the Battle of Baghuz Fawqani, after which the group was forced into an insurgency. IS's leader, Abu Bakr al-Baghdadi, died during a US special operations raid in northern Syria in October 2019 and was succeeded by Abu Ibrahim al-Hashimi al-Qurashi. In August 2020, over 10,000 IS fighters were estimated to remain in Syria and Iraq, mainly as sleeper cells.
International coalitions against the Islamic State
On the margins of the 4/5 September 2014 NATO summit in Wales, on 5 September 2014, U.S. Secretary of State John Kerry invited Ministers of Australia, Canada, Denmark, France, Germany, Italy, Turkey and the United Kingdom, for a separate meeting
in which he pressed them to support the fight against ISIL militarily and financially. Those nine countries agreed to do so by supporting anti-ISIL forces in Iraq and Syria with supplies and air support, according to a statement that day from Kerry and U.S. Secretary of Defense Hagel. In September 2014, Jordanian and Saudi Air Forces began their co-ordination with United States to wage a joint aerial bombing campaign against IS bases in its territories across Iraq and Syria.
On 17 October 2014, the Department of Defense formally established Combined Joint Task Force – Operation Inherent Resolve (CJTF-OIR)—"in order to formalize ongoing military actions against the rising threat posed by ISIS in Iraq and Syria."
On 3 December 2014, at the NATO headquarters in Brussels, diplomats and foreign ministers from 59 countries gathered to plot a way forward against the threat of ISIL. U.S. Secretary of State John Kerry told the gathering, that "defeating the ideology, the funding, the recruitment" of Daesh (ISIL) must be the primary focus of their discussion, more important than airstrikes and other military action.
The countries represented on 3 December were: the nine countries of the above-mentioned 5 September coalition in Wales (see above); the extra 18 countries of the 15 September France-led coalition in Paris (see below) except for China and Russia; and 33 additional countries: Albania, Austria, Bosnia-Herzegovina, Bulgaria, Croatia, Cyprus, Estonia, Finland, Georgia, Greece, Hungary, Israel, Iceland, Ireland, Kosovo, Latvia, Lithuania, Luxembourg, Macedonia, Moldova, Montenegro, Morocco, New Zealand, Portugal, South Korea, Romania, Serbia, Singapore, Slovakia, Slovenia, Somalia, Sweden, Taiwan and Ukraine.
They styled themselves as the Global Coalition to Counter the Islamic State of Iraq and the Levant (ISIL), and agreed to a strategy that included:
cutting off ISIL's financing and funding;
supporting military operations.
On 15 September 2014, at the 'International Conference on Peace and Security in Iraq' hosted by the French President François Hollande in Paris, 26 countries were represented: the countries of a US-led coalition that on 5 September in Wales (see above) had agreed on a coalition against ISIL except Australia and Poland, and furthermore Bahrain, Egypt, Iraq, Jordan, Kuwait, Lebanon, Oman, Qatar, Saudi Arabia, United Arab Emirates, Belgium, China, Czech Republic, Japan, the Netherlands, Norway, Russia and Spain. They committed themselves to supporting the Iraqi government with military assistance in its fight against ISIL, and they reaffirmed their commitment to UNSC Resolution 2170 of 15 August (condemning all trade with ISIL and urging to prevent all financial donations and all payments of ransoms to ISIL), so reported the French government.
In retaliation for the November 2015 Paris attacks, the French Air Force significantly intensified airstrikes against ISIL targets in Syria, hitting among other targets the Syrian city of Raqqa, the de facto capital of ISIL. The French Navy deployed the aircraft carrier Charles de Gaulle with eighteen Rafale, eight Mirage 2000, two E-2 Hawkeye and 4 helicopters. The aircraft carrier travelled with the frigate Chevalier Paul and HMS Kent.
At the end of September 2015, Russia, Iraq, Iran and Syria set up a 'joint information center' in Baghdad to gather, process and analyse intelligence regarding ISIL and operations near the Syria-Iraq border. On 30 September 2015, Russia began its air campaign on the side and in support of the Syrian government.
Russia was also reported to have reached agreements on co-ordination of operations in Syria with Jordan and Israel.
On 14 March 2016, Russian President Vladimir Putin announced a partial withdrawal from Syrian territory, citing the success of the ongoing ceasefire and greater security of the Syrian government.