Sunni hostage Kassig beheaded by ISIS militants in new video released online . Gerges : Peter Kassig 's beheading reveals a terror group that is desperate and on the run . Gerges : American -led airstrikes are working and ISIS ' leaders are being driven underground . Gerges : ISIS tribes that were loyal to Sunni are now peeling off amid the group 's ongoing brutality .
American hostage Peter Kassig beheaded by ISIS militants in new video released online . Gerges : Kassig 's beheading reveals a terror group that is desperate and on the run . Gerges : American-led airstrikes are working and ISIS ' leaders are being driven underground . Gerges : Sunni tribes that were loyal to ISIS are now peeling off amid the group 's ongoing brutality .