The Turkmen are ethnic Turks who have lived in the region of Syria, Iraq and Iran since the 11th Century.
They are mainly concentrated in the north, in the Turkmen Mountain area in Latakia close to the Turkish border, as well as in Aleppo, Idlib, Homs, Tartus and the Damascus region.
There are no reliable population figures, but they are estimated to number between about half a million and 3.5 million.
Under the Assad regimes in Syria, the Turkmen were banned from publishing or writing in Turkish. The government did not recognise them or other ethnic groups as minorities, preferring to stress the unity of the Arab nation.
Supported by Turkey, a staunch foe of Bashar al-Assad, they took up arms against the regime soon after the start of the uprising in 2011.
Syrian Turkmen parties also united under the Syrian Turkmen Assembly, which is affiliated to Syria's Western- and Gulf-backed National Coalition opposition group.
The Turkmen have formed numerous Turkish-trained rebel groups, including the Syrian Turkmen Brigades, reported to be about 2,000 - 10,000 strong, in 2012.
Their military structure is loose and they maintain a number of units in northern Syria.
Their brigade in Latakia Province, the Jabal al-Turkman Brigade, was formed in 2013 and comprises 12 armed units.
Its Second Coastal Division was formed in early 2015 and is closely affiliated with the Western-backed rebel Free Syrian Army (FSA).
Reports say the brigades work with other opposition armed groups in the northern Latakia countryside, including the FSA, the al-Qaeda affiliated Nusra Front and the Islamist Ahrar al-Sham.
The area has often been the flashpoint of clashes between the brigades on the one hand, and the Syrian army, Iranian forces and Lebanese Hezbollah on the other, who enjoy Russian air support.
Their main opponents are the regular Syrian army and the Islamic State (IS) militant group.
A further unit - the Sultan Selim Brigade - has long sided with the Kurdish-led People's Protection Units (YPG) and joined the US-backed Kurdish-led opposition coalition called the Syrian Democratic Forces (SDF) on 10 October.
The Turkmen fighters also took part in earlier YPG-led offensives against IS.