Jordan's King Abdullah II vowed to wage a "relentless" war against the ISIS militant group one day after the group executed a captured Jordanian fighter pilot."The blood of hero pilot Moaz al-Kasasba will not go unpunished," Abdullah said at a meeting with top army brass, the Jordanian Royal Court said in a Wednesday statement."The response by Jordan and its army to this criminal and cowardly act will be devastating," he said."This terrorist organization (the ISIS) does not only fight us, but also fights Islam and its peaceful teachings," the Jordanian monarch said.An online video purportedly showing al-Kasasba being burnt alive by his ISIS captors went viral on Tuesday.The gruesome murder sparked anger in the Hashemite kingdom, which was already a member of an ongoing U.S.-led air campaign against the militant group.Shortly after the appearance of the video, Jordanian authorities executed two Iraqi nationals-Sajida al-Rishawi and Ziyad al-Karbouli-who had been on death row since 2006 after being convicted of terrorism by a Jordanian court.Last summer, the ISIS captured large swathes of land in Iraq and Syria, killing thousands of people in the process. It later declared the captured territories to be part of a self-styled "Islamic caliphate."Since the group captured the northern Iraqi city of Mosul in June of last year, a U.S.-led coalition-which includes Jordan-has carried out numerous airstrikes against ISIS targets in both Iraq and Syria.