>> for opportunities to sow chaos because they believe it will tip the scales eventually toward a Caliphate.

From what I've been told and read, they've already established a Caliphate. The primary driver of having a Caliphate is that ISIS must control territory, without controlling territory, there is no Caliphate - correct?

This was one of the best explanations I've read about why ISIS is doing what it is doing:

http://www.theatlantic.com/magazine/archive/2015/03/what-isi...

If it loses its grip on its territory in Syria and Iraq, it will cease to be a caliphate. Caliphates cannot exist as underground movements, because territorial authority is a requirement: take away its command of territory, and all those oaths of allegiance are no longer binding.