They also originally stemmed from Al-Qaeda in Iraq, but they are mortal enemies of ISIS.
Al Nusra and the ISIS are not mortal enemies. For sure there are some differences between the two, but they are united by their common enemy (Bashar al Assad). And both the organisations receive funding from the Saudi and Qatari royal families, who exert a lot of influence over them. To this date, both the terrorist groups remain affiliated to the Al Qaeda.
None of that is even remotely true.
Al Nusra and the ISIS are not mortal enemies.
They've been fighting on-and-off since at least February (
Just one example of a source).
They have killed hundreds of each other's men (
Source), including senior figures (
Source, one of many). How else could you possibly define mortal enemies?
they are united by their common enemy (Bashar al Assad).
Both have been fighting each other (and other rebel groups) far more than Assad in recent months. This is sometimes credited as one of the main reasons for Assad's recent regained strength in many key areas. In fact, Jabhat al-Nusra (and other rebels) often accuse ISIS of tacitly collaborating with Assad by targeting mostly other rebels (
Source, also see previous source).
And both the organisations receive funding from the Saudi and Qatari royal families, who exert a lot of influence over them.
These are silly rumors. The Saudis and Qataris (together with the US, Turkey and others) have been funding the moderate rebels who fight against both Jabhat al-Nusra and ISIS. They have no interest in funding either one of these organizations. Show me one half-credible source for this claim.
To this date, both the terrorist groups remain affiliated to the Al Qaeda.
Well, this is very famously false (
Source,
source and
source).