At least 13 rebel groups inside Syria rejected the authority of the Syrian National Coalition, which supports bringing an end to the reign of the oppressive Assad regime. Though the rebels want essentially the same thing, they would prefer an Islamic state without the help of a moderate Western-backed military force. These 13 groups are among the strongest rebel units in the country. Their diversity of views and objectives indicates the complicated sociopolitical nature of Syria. (Sources: Dominic Evans, Alastair Macdonald, Reuters; Yahoo News)
NUSRA FRONT - Allied to al Qaeda leader Ayman al-Zawahri. Also known as Jabhat al–Nusra. Designated terrorist group by U.S.; one of the most potent forces against President Assad, using suicide bombers to attack military targets. Fighters often coordinate with other brigades.
AHRAR ASHAM - Leading radical Salafist (fundamentalist Sunni Islam) group, focus in north-west. Shares much of Nusra Front's Islamist agenda but criticizes its allegiance to al Qaeda.
TAWHEED BRIGADE - Led assault on Aleppo in mid-2012. Believed to be the largest militant group in Aleppo province. Some members favor Islamic state in Syria; others more secular.
SUKOUR AL-SHAM - Concentrated in the northern province of Idlib and parts of Hama, Sukour al-Sham was driving force behind establishment late last year of Syrian Islamic Liberation Front.
ISLAM BRIGADE - Another component of Syrian Islamic Liberation Front; driving force of rebel operations around Damascus. It claimed a July 2012 bombing that killed close security aides to Assad.
LIWA AL-HAQ - Formed last year in Homs; made up of Islamist units fighting in and around the central city. It is led by a former paratrooper in the Syrian armed forces.
HARAKAT FAJR ASHAM AL-ISLAMIYA - Aleppo-based Salafist group created by a three-way merger in January.
NOUR AL-DIN AL-ZINKI BATTALION - Saudi-backed, Aleppo-based Islamist unit. Members seen in recent video showing their new weapons, including anti-tank missiles.
FURQAN BRIGADE (AL QUNEITRA) - A branch of the Damascus-based Islamist Furqan Brigade, operating in southwest of Syria near the Israeli-occupied Golan Heights.
LIWA AL-ANSAR - Fighting to the west of Aleppo and in Idlib. Seized a military post from Assad's forces in March.
19TH DIVISION - Rebel unit operating in Aleppo, including Khan al-Assal. Closely linked to Ansar Brigade. Its Facebook page identifies it as part of the Free Syrian Army.
TAJAMU FASTAQM KAMA AMART - Formed in December from nine units in Aleppo province.
HARAKAT AL-NOUR AL-ISLAMIYA - Aleppo-based Islamists identified in a July video as one of the rebel factions involved in ongoing fighting in the northern town of Khan al-Assal.