Al-Qaeda's Syrian wing, Jabhat al-Nusra, has turned on one of their traditional allies in Idlib Province, the US-backed Free Syrian Army wing called Division 13, accusing the group of planning to attack its own bases.
Nusra followed this up with attacks on the Division 13 bases, seizing both bases and a number of US-made anti-tank missiles from the group. The Syrian Observatory for Human Rights reported a number of FSA fighters were detained.
Nusra dominates the Idlib Province as the head of a coalition of Islamist-leading rebel factions. This coalition includes, or at least included multiple US-backed factions who are recipients of US arms. The US has expressed concern about Russian airstrikes against Idlib, even if targeting al-Qaeda, on the grounds they threaten American allies.