The pullout follows an agreement reached earlier with the Iraqi government. Department of Defense spokesman Sean Parnell called it "the successful conclusion of the military mission that defeated ISIS in Iraq," pointing to a 12-year campaign against the group.
Parnell said the withdrawal marks a shift away from what he described as a "wartime" footing in the country, though the statement didn't detail the full scope of that transition. Since the group seized large parts of Iraq and Syria more than a decade ago, the operation had been the primary U.S.-led military effort against ISIS.
For Iraq, the departure closes out over a decade of direct coalition military presence tied to the fight against the group. It also raises questions about what security arrangements, if any, replace the coalition's role in the region going forward, and how Iraqi forces manage without that backup.