Islamic State (IS), Sunni Islamic militant group committed to the establishment of an Islamic caliphate that would unite Muslims in a transnational, strict-fundamentalist Islamic state. IS is mainly active in Iraq and Syria, but has stated a goal of extending its reach to other countries in the E Mediterranean. Its origins lie in Al-Tawhid wa al-Jihad, founded after the U.S. invasion of Iraq (2003) and headed by Abu Musab al-Zarqawi. The group mounted terror attacks, including videotaped beheadings and suicide bombings, against U.S. forces and Shiites in Iraq and also conducted attacks in Jordan. In 2004 Zarqawi publicly aligned with Al Qaeda, and the group became known as Al Qaeda in Iraq. Zarqawi was killed in 2006. The Islamic State in Iraq was then formed by the group and other militant Sunni Islamists, but U.S.-led operations weakened it. In 2010 Abu Bakr al-Baghdadi became its leader. He revived its terrorist activities and turned it a significant military force whose members included former officers from Saddam Hussein's army. It expanded into Syria after the outbreak (2011) of civil war and renamed itself (2013) the Islamic State in Iraq and the Levant (also known as the Islamic State in Iraq and Syria). In 2014 it seized significant territory in N Iraq, routing poorly led Iraqi forces and securing large quantities of arms. The group also broke with Al Qaeda, renamed itself the Islamic State, and proclaimed a caliphate headed by Baghdadi. A number of Islamic militant groups formerly aligned with Al Qaeda realigned with IS, and IS's successes have led to an influx of foreign Muslims into its ranks. Boko Haram allied itself with IS in 2015, and that year IS also established a presence in Sirte, Libya, and claimed responsibility for a terror attacks in in Saudi Arabia, Egypt, and other countries. The group's tactics since its resurgence have been 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 and shrines, archaeological ruins, and artifacts and books it considers un-Islamic. The group's successes in Iraq also 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.