It can be argued that the fondness of the Islamic State for beheading people can be traced to Quran 47:4 ("When you encounter the unbelievers on the battlefield, strike off their heads until you have crushed them completely"). Do you agree?

In addition to Quran 47:4, this hadith could well have had an impact on the tendency of the Islamic State (ISIS) to behead people:  "The Jews were made to come down, and Allah's Messenger imprisoned them.  The the Prophet went out into the marketplace of Medina (it is still its marketplace today) and he had trenches dug in it.  He sent for the Jewish men and HAD THEM BEHEADED in those trenches.  They were brought out to him in batches.  They numbered 800 to 900 boys and men. (al-Tabari, vol. 8, p. 35).