Irregular war : ISIS and the new threat from the margins

To what extent does ISIS pose an existential danger to our world? Or is it merely a threat from the margins of inherently unstable states in faraway places? Should ISIS be feared because of its future access to weapons of mass destruction? Or is it simply adept at grabbing land as well as headlines? ISIS (or the Islamic State) is the most dramatic expression of a new era in international politics: uprisings which transform into "irregular warfare...