Lessons of war: David Petraeus warns that a bigger challenge awaits after Islamic State is driven from Mosul

The Iraqi security forces [are] this mix of Iraqi army, Iraqi police, Kurdish peshmerga, the Iraqi counter-terrorism service, the Iraqi air force, popular mobilization units — some Shia Arab from the south, some Sunni Arab from the tribes of Nineveh province. And the challenge is going to be, first of all, to keep all of them pulling in the same direction. But the real issue, the real battle, of course, is the battle after the battle for Mosul, and that is the struggle for power and resources in one of the biggest and most complex provinces in all of Iraq.