The Islamic State of Iraq and the Levant (ISIL ), also known as the Islamic State of Iraq and Syria (ISIS ), officially known as the Islamic State (IS) and also known by its Arabic-language acronym Daesh (Arabic: داعش, romanized: Dāʿish, IPA: [ˈdaːʕɪʃ]), is a terrorist militant group and a former unrecognised proto-state that follows a fundamentalist, Salafi jihadist doctrine of Sunni Islam. ISIL gained global prominence in early 2014 when it drove Iraqi government forces out of key cities in its Western Iraq offensive, followed by its capture of Mosul and the Sinjar massacre.
The group has been designated a terrorist organisation by the United Nations as well as by many international organisations and individual countries. ISIL is widely known for its videos of beheadings and other types of executions of both soldiers and civilians, including journalists and aid workers, and its destruction of cultural heritage sites. The United Nations holds ISIL responsible for committing human rights abuses, crimes against peace, genocide, war crimes, and crimes against humanity. ISIL also committed ethnic cleansing on a historic and unprecedented scale in northern Iraq.
ISIL originated as Jama'at al-Tawhid wal-Jihad in 1999, which pledged allegiance to al-Qaeda and participated in the Iraqi insurgency following the 2003 invasion of Iraq by Western forces at the behest of the United States. In June 2014, the group proclaimed itself a worldwide caliphate and began referring to itself as the Islamic State (الدولة الإسلامية ad-Dawlah al-Islāmiyah; IS). As a caliphate, it claimed religious, political, and military authority over all Muslims worldwide. Its adoption of the name Islamic State and its idea of a caliphate have been widely criticised, with the United Nations, various governments, and mainstream Muslim groups vehemently rejecting its statehood.
In Syria, the group conducted ground attacks on both government forces and opposition factions, and by December 2015, it held a large area extending from western Iraq to eastern Syria, containing an estimated 8 to 12 million people, where it enforced its interpretation of sharia law. ISIL is believed to be operational in 18 countries across the world, including Afghanistan and Pakistan, with "aspiring branches" in Mali, Egypt, Somalia, Bangladesh, Indonesia, and the Philippines. In 2015, ISIL was estimated to have an annual budget of more than US$1 billion and a force of more than 30,000 fighters.
In mid-2014, an international coalition led by the United States intervened against ISIL in Syria and Iraq with a massive airstrike campaign, in addition to supplying advisors, weapons, training, and supplies to ISIL's enemies in the Iraqi Security Forces and Syrian Democratic Forces. This campaign reinvigorated the latter two forces and dealt a huge blow to the nascent Islamist proto-state, killing tens of thousands of ISIL troops and dealing significant damage to their financial and military infrastructure. This was soon followed by a smaller-scale Russian intervention exclusively in Syria, in which ISIL lost thousands more fighters to airstrikes and other Russian military activities and had its financial base even further degraded. In July 2017, the group lost control of its largest city, Mosul, to the Iraqi army, followed by the loss of its de facto political capital of Raqqa to the Syrian Democratic Forces. Following these major defeats, ISIL continued to lose territory to the various states and other military forces allied against it, until it controlled no meaningful territory by November 2017. US military officials and simultaneous military analyses reported in December 2017 that the group retained a mere 2 percent of the territory they had previously held. On 10 December 2017, Iraq's Prime Minister, Haider al-Abadi, said that Iraqi forces had driven the last remnants of the Islamic State from the country, three years after the militant group captured about a third of Iraq's territory. By 23 March 2019, ISIL lost one of their last significant territories in the Middle East in the Deir ez-Zor campaign, surrendering their "tent city" and pockets in Al-Baghuz Fawqani to the Syrian Democratic Forces at the end of the Battle of Baghuz Fawqani.
Abu Bakr al-Baghdadi, the leader of ISIL since 2013, later killed himself by detonating a suicide vest during a raid into the rebel-held Idlib province of Syria conducted by U.S. special forces on 27 October 2019. On 31 October, ISIL media announced Abu Ibrahim al Hashimi al-Qurayshi to be Baghdadi's successor.