Here's a crazy map of the land ISIS wanted to take over, made back in 2006 at the height of their Iraq war-era power:
So yeah. It looks a whole like ISIS' plan, given the contours of the map, is to take over oil lands in eastern Iraq and western Syria.
There's something else chilling about that map. Aaron Zelin, a fellow at the International Centre for the Study of Radicalisation and Political Violence and the guy who first dug up this map, points out that they've actually managed to take a lot of that land in recent months. The implication — that ISIS may have executed a strategy first developed at least 8 years ago — suggests the group is way better at strategic planning than you might think.