They do it to show they can do whatever they want, and to show they don’t need to accept Western morality or “rules of engagement” or logic or any other standard of behavior connected with the WestThe author said
These condemned men do not deserve to die. They have done nothing wrong. Yet we kill them anyway, and we do so in our own way, without any pretense of any relationship between us. We do not recognize any mutual obligations between us and our victims. We do not seek their sanction, nor do we seek the world’s. We do not pretend to care about justice. We kill because we can.And I agree with you both. They're expressing their rejection of the west, and their belief they will prevail over western values.
I'm not rejecting the Islamic support for beheading mentioned by many on the thread. But the Islam connection is the need for dominance over the infidel. Beheading is simply a means which gets our attention. You'll recall the burning and hanging of bodies in Iraq a decade or so. Got some play in the media, but nothing like this. If it had, they'd be burning journalists. Recall the War of Jenkins' Ear. If it could attract the attention they need for recruiting they'd be chopping off ears. They're sending us a message
Cause and effect...
Revelation 20:4 And I saw thrones, and they sat on them, and judgment was committed to them. Then I saw the souls of those who had been beheaded for their witness to Yeshua and for the word of ELoHIM, who had not worshiped the beast or his image, and had not received his mark on their foreheads or on their hands. And they lived and reigned with Moshiach for a thousand years.
Mark in the forehead...
Quran
Surat Al-Fatĥ
48:29 Muhammad is the Messenger of Allah ; and those with him are forceful against the disbelievers, merciful among themselves. You see them bowing and prostrating [in prayer], seeking bounty from Allah and [His] pleasure. Their mark is on their faces from the trace of prostration. That is their description in the Torah. And their description in the Gospel is as a plant which produces its offshoots and strengthens them so they grow firm and stand upon their stalks, delighting the sowers - so that Allah may enrage by them the disbelievers. Allah has promised those who believe and do righteous deeds among them forgiveness and a great reward.
You get marked in the forehead from bowing to Mecca...