ISIS is a transitory organisation whose aspiration to lead an Islamic reconquista is doomed to fail. It will eventually be degraded and splinter, some of its members joining the myriad other groups within the jihadist milieu while others fight over what is left of ISIS. One thing of enduring interest about the ISIS experience, however, is the way it has understood the Western (and local) media cycle and exploited it. 

Grotesque images of beheadings and of Western jihadis spewing forth their intolerant bile are without doubt sickening, but they serve a purpose. One of the enduring principles of war is the maintenance of momentum. Once lost, it is difficult to recover. ISIS has certainly lost its battlefield momentum and is unlikely to recover it. That's why it is trying to maintain momentum through the media.

Like all good PR practitioners, ISIS's PR jihadis understand that in order to give the impression of dominance even when you don't possess it, it is necessary to replace bad news with something that suits your purposes. Hence each video release has coincided with images that ISIS would prefer did not get much airplay.

Note that the latest video showing the beheading of Peter Kassig and Syrian military personnel was released a day or two after the fall of the town of Bayji to Iraqi government forces.

The release of the video of the 17 year-old Australian Abdullah Elmir ranting to camera surrounded by his Lord of the Flies fan group followed a day after spectacular photos of US bombing raids against ISIS targets around Kobane hit our screens. Guess what dominated the media — images of thousands of pounds of high explosive blasting ISIS positions in Syria in the meat grinder of Kobane or a 17 year-old with a rifle blathering on about not much? The latter, of course.

This is part of a broader pattern. A day after the Turkish parliament authorised military action against ISIS (not good news for ISIS), video of the beheading of British aid worker Alan Henning was released. And if we hark back to the recapture of Mosul Dam by Kurdish forces backed by US air support in mid-August, the beheading of US journalist James Foley followed shortly after. 

None of these actions are designed to dissuade Western military intervention in Iraq or Syria, or even to goad the West into becoming decisively committed on the ground, because ISIS understands this is unlikely to occur. Rather, it has a much more short-term aim: to get ISIS's military and political setbacks out of the media cycle and replace them with bloody imagery that demonstrates ISIS is still a force. We should not, however, confuse media momentum with battlefield momentum. ISIS may have the former, but it has lost the latter.