I have to say that credit must be given where credit is due. Mohammad successfully united a group (the Arabs) that before and since have never been completely united, nor successfully governed by one of their own. (I consider that the khalifa's who held the Caliphate together for a while, did so mostly on the residual strength of Mohammad.)

Additionally, today AQ, Hizbollah, and Hamas, and other similar groups draw inspiration from that success. I believe this is why beheading is popular among this type of group, because they believe (rightly or wrongly) that it was something done by Mohammad and his followers. After all socialist insurgents and terrorists, even Arab ones, usually just shot their victims. I believe that a study of the correlations between Ancient Jihad (that of Mohammad, and his immediate followers) and the modern "Jihad" may be in order. Perhaps it is worth considering that because these organizations look to the past for their spiritual inspiration, they will also do so for their tactical inspiration. It may well be that the enemies playbook is just history itself.