Their days in Lebanon seem numbered, but no thanks to the Lebanese army
Last week the Lebanese PM declared the Lebanese Army would soon launch an offensive against al-Qaeda's enclave in Lebanon known as the Arsal barrens. Being Saudi-backed the Sunni PM also claimed this would be a strictly Lebanese army operation with no coordination with Hezbollah or the Syrian army.
Over the weekend an offensive has indeed been launched but the truth is exact opposite of what the PM Hariri promised. It sees Hezbollah advancing against al-Qaeda, backed by the Syrian air force, and with the Lebanese army playing a distinctly minor role.
Hezbollah, which has assembled a big part of its armor for the operation, is advancing against the part al-Qaeda enclave in Lebanon, while the Syrian army augmented by Hezbollah is simultaneously rolling back the part of the enclave in Syria. They are both supported by the Syrian air force.
Actually there is not a critical need for Syrian air strikes to support Hezbollah, since the group has acquired so much artillery in Syria, but nonetheless the Syrian air force repeatedly struck al-Qaeda and ISIS in Lebanon in preparation for the offensive.
The Lebanese army for its part has simply dug in deeper and occupied some sites abandoned by al-Qaeda after Hezbollah pressure.
The south of the Arsal barrens area is held by Syrian al-Qaeda (Hayat Tahrir al-Sham) and the north by ISIS. Actually the Syrians have reportedly already taken back the part held by HTS on their side, with only the ISIS part remaining.
The area came under control of ISIS and al-Qaeda in 2013. After Hezbollah's entry into the war the two were forced to retreat from nearby western Syrian towns, and fled to Arsal barrens — area which was previously almost unpopulated but now hosted tens of thousands of refugees.
The groups took control of the refugee camps and on multiple occasions also attempted to take control of the nearby Lebanese town of Arsal (and once briefly succeeded) leading to clashed with the Lebanese army. The latest clashes with the Lebanese army occurred last month when a Lebanese sweep of the camps for terrorists saw seven Lebanese soldiers wounded, and one civilian killed, supposedly by five suicide bombers.
After the rebel-ISIS split in early 2014, the enclave was formally divided with ISIS reigning in the north, and Jabhat al-Nusra (now HTS) controlling the south.