They're meant to be shocking, and they are. The decapitation murders of hostages in Iraq and Saudi Arabia represent an escalation of tactics by Al Qaeda-linked groups in their campaign to sow fear and helplessness among their opponents.
But it may be important to remember that the motivation for these brutal acts is modern. There is nothing Islamic, or traditionally Middle Eastern, about beheadings, say experts. Instead, they represent another adaptation by a cruelly imaginative terrorist movement, the next new thing from people who pioneered the use of hijacked airliners as weapons.
"There's nothing particularly religious about this," says Asma Afsaruddin, associate professor of Arabic and Islamic studies at the University of Notre Dame. "It's absolutely morally reprehensible."
It's true that Saudi Arabia employs public decapitation as its means of capital punishment. Last year the Saudis executed 53 criminals convicted of everything from murder to lesser crimes such as drug offenses. And Islamist terrorists have employed the technique in the recent past. Chechen rebels have videotaped some beheadings. During Algeria's long war against French occupation, one Muslim rebel leader even wrote a pamphlet trying to justify his group's use of beheadings in religious terms.
But throughout history many cultures have employed decapitations as punishment at one point or another. The wives of Henry VIII and Marie Antoinette were among past famous victims.
More recently, the Japanese subjected some prisoners to beheading during World War II, though the extent of Japan's use of the practice remains unclear. France last used the guillotine in 1977.
While Al Qaeda and its allies may claim religious justification for their actions, there is nothing in the Koran justifying beheadings. Indeed, there is nothing in the literature of mainstream Islam that justifies the killing of innocents in any form, say experts.
The Council on American-Islamic Relations, based in Washington, has called the recent trend of brutal violence "senseless." A statement from the group says it repudiates "all those who believe such murderous behavior benefits the faith of Islam or the Muslim people..."