The group expanded into Syria after the outbreak (2011) of civil war, seized significant territory there, and renamed itself (2013) the Islamic State in Iraq and the Levant (ISIL); it was also known as the Islamic State in Iraq and Syria (ISIS). In 2014 it seized significant territory in N and W Iraq, routing poorly led Iraqi forces, securing large quantities of arms, and establishing control over roughly a third of Iraq. The group also broke with Al Qaeda, renamed itself the Islamic State, and proclaimed a caliphate headed by Baghdadi. Within territory it controlled, the group's tactics were especially brutal, including videotaped beheadings, the slaughtering of captured enemy forces and of civilians regarded as infidels, forced conversions and enslavements, and the destruction of mosques, churches, and shrines, archaeological ruins, and artifacts and books it considers un-Islamic. IS also has been accused of using chemical weapons.
A number of Islamic militant groups formerly aligned with Al Qaeda realigned with IS, and IS's successes led to an influx of foreign Muslims into its ranks. Boko Haram and some former Pakistani Taliban in Afghanistan allied themselves with IS in 2015. IS also established a presence in Libya, where they controlled Surt (Sirte; 2015–16). At the same time, the group's successes in Iraq led to air strikes by the United States against IS forces beginning in Aug., 2014, at first in Iraq, but later in Syria as well, and the subsequent creation of an informal international military coalition to defeat IS. IS subsequently suffered significant setbacks in Iraq and Syria, losing all of the territory it once controlled by the end of 2017 and early 2019, respectively. Forced into hiding in largely uninhabited areas, it has turned increasingly to guerrilla terror attacks in those nations. In 2019 al-Baghdadi killed himself during a U.S. raid on his hideout; Abu Ibrahim al-Hashemi al-Qurayshi (nom de guerre of Amir Mohammed Abdul Rahman al-Mawli al-Salbi) succeeded him as IS leader. IS also has conducted or inspired an increased number of terror attacks around the world and in parts of Iraq not under its control. Since late 2015 terrorists associated with IS have bombed a Russian charter plane over the Sinai peninsula and mounted deadly terror attacks in Beirut, Paris, Brussels, Saudi Arabia, and elsewhere.
See studies by J. Stern and J. M. Berger (2015), J. Warrick (2015), M. Weiss and H. Hassan (2015), and F. A. Gerges (2016).
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