Gaining GroundThe spread of Iraqi al Qaeda groups in Syria
Late 2011 The Islamic State of Iraq, or ISI, al Qaeda's Iraq branch, moves operatives to Syria to set up a new affiliate, Jabhat al-Nusra.
January 2013 Al-Nusra, led by Abu Muhammad al-Golani, announces itself as an official entity in online videos. In the months that follow, al-Nusra becomes a leading Syrian rebel fighting force, attracting thousands of jihadists, including foreigners. It also provides social services in parts of northern Syria—and ends up designated by Washington as a foreign terrorist organization.
April ISI leader Abu Baker al-Baghdadi changes the name of ISI to Islamic State of Iraq and al-Sham, or ISIS, in an attempt to swallow Jabhat al-Nusra into a broadened entity. Al-Nusra's leader, al-Golani, rejects the plan, pledging allegiance to central al Qaeda chief Ayman al-Zawahiri.
Spring 2013 In the months that follow, the two groups separate. Syrian jihadists leave al-Nusra for ISIS. ISIS begins to attract thousands of foreign fighters to Syria.
June 13 At conference in Cairo of regional Sunni clerics, over 100 prominent religious leaders sign a document urging jihad in Syria; more foreign fighters flock to the civil war.
Aug. 15 ISIS pushes FSA unit the Ahfad al-Rasoul brigades out of the city of Raqqa, after detonating several suicide car bombs, including one that destroyed the brigades' headquarters there.
Sept. 10 A leader of hard-line Islamist group Ahrar al-Sham is killed after a clash at an ISIS checkpoint in Idlib.
Sept. 11 Al Qaeda chief al-Zawahiri urges Islamists fighting in Syria not to work with the secular opposition. He also calls for 'lone-wolf' or small-scale attacks to damage the U.S. economy.
Sept. 11 Syrian government warplanes bomb a field hospital in al-Bab, a town in Aleppo under ISIS control. Residents and FSA fighters respond by attacking the ISIS headquarters in the town.
Sept. 12 ISIS fighters take over a base in eastern Hama including a depot with dozens of rockets, rocket launchers and armored vehicles.
Sept. 13 ISIS's eastern Aleppo unit declares war on its rivals in a campaign it named 'Expunging Filth,' identifying two FSA units by name.
Sept. 18 ISIS and an FSA-allied unit clash in Azaz, an Aleppo town 2½ miles from the Turkish border. An opposition activist in the town said ISIS attacked the unit for trying to obstruct the al Qaeda group from arresting a German doctor working at an Azaz field hospital.