It certainly is looking that way, especially if the latest beheading videos are real.
BBC News - Japan checking IS 'hostage death' videoJapanese government official Yoshihide Suga condemned the latest video as "outrageous and unacceptable".
Are beheadings enough to go to war? It seems like in the past we have gone to war over much, much less. I guess it's harder because ISIS isn't technically a country...yet.