Turkish officials announced Wednesday that they sent hundreds of additional special forces, along with tanks, armored vehicles, and other equipment, across the border into Syria’s Idlib Province. They are intended to reinforce Turkish military posts in northern Syria.

Turkish officials say that the intention is to deter the Syrian military from launching an offensive against the Idlib Province, which is under the control of various Islamist rebel factions, the largest of which is al-Qaeda’s Nusra Front. Turkey is aligned with some of these fighters in supporting regime change in Syria.

In addition to boosting their direct military presence in Idlib, Turkey haas also sent a large amount of additional weapons and ammunition for the rebels to use. Rebel sources say they have been told Turkey will provide military support “for a long, protracted battle.”

Idlib and neighboring areas are the last major rebel enclave inside Syria. For Syria to recover the territory would effectively end the war, though doing so is likely to take a major offensive. Syrian and Russian planes have been conducting airstrikes along the outskirts, trying to soften up defenses before a ground invasion. There is no timetable for such an invasion.