They have been rolling as a land force for the past three years. That's how they've managed to control towns and cities in the open. This is nothing like the insurgency.
Not as a conventional land force though - the bulk of their forces have stayed highly mobile utilising pickups, etc. so as be to be hard to pin down or force into a direct firefight - sure there is some times where they have taken more of a stand or pushed to hold territory while those against them are on the backfoot.