"A glimpse at how the sectarian conflict in Iraq will widen upon the departure of US troops, siphoning off money, arms, and personnel that jihadists could otherwise employ against nonbelievers." -- from Robert Spencer's comment here
That would be too easy. That would be too obvious. It simply cannot be considered. It wouldn't be fair. It wouldn't be right. We broke it, we fix it. We can't conceivably let Saudi Arabia and the Islamic Republic of Iran fight a proxy battle in Iraq. That would be wrong.