Terrorism has long had a gruesome role in conflicts, often among revolutionary groups so fanatically certain of their ends that they readily justify the most barbaric of means. But it can also turn with a vengeance against those who inflict it, as the Islamic State is learning with its most recently publicized atrocity — murdering a Jordanian air force pilot by burning him alive. The video of the killing was meant to dissuade Arabs from participating in the Western coalition against the group; instead, it has succeeded in fostering rage and revulsion against the jihadists throughout the Arab world.

The Islamic State, the group also known as ISIS or ISIL, or “Daesh” among Arabs, has achieved a low in the annals of terrorism through its use of the Internet to post videos and images of executions, most by beheading, of bound, kneeling hostages — including, lately, two Japanese men. Although ISIS has inflicted death and inhumane torture on Arabs in its areas of operation in Syria and Iraq, feelings toward the group within various parts of the Arab world had been mixed, with many Arabs professing either indifference or varying degrees of sympathy for the jihadists. Jordan, a strong ally of the United States in the fight against ISIS, was also the largest source of recruits for the group.

That changed after ISIS posted a video on Tuesday of the captured Jordanian pilot, First Lt. Moaz al-Kasasbeh, being burned alive in a cage. The killing had apparently taken place in early January, though ISIS cynically continued proposing to swap him for prisoners in Jordan until negotiations broke down after Jordan demanded proof that the pilot was alive. The Middle East erupted in fury at the video of the execution. The Islamic prohibition against immolation may have been a factor in the outpouring of anger among Arabs.

King Abdullah II of Jordan promptly ordered the execution of two jihadists already sentenced to death in Jordan, and was welcomed by cheering crowds on his return from a visit to Washington. On Thursday, Jordanian planes responded by bombing Islamic State targets. Leaders in other nations condemned the murder of the pilot, and a grand imam in Cairo called for ISIS leaders themselves to face medieval-style executions.