300 -350 k were fighting against ISIS
20-50 K in Syria
During over decades of insurgency should be millions of veterans available in Iraq (fought in one or more wars and insurgency against the US occupation AAH , Kataib Hezb etc )
Rotations of personal in and out
If it comes to sustained long campaign , Idlib jihadist are in trouble (as the ukrops of vanishing manpower)