Here's an unwelcome fact. At the fall of the Ottoman Empire after the first world war, Britain had 410,000 troops in Iraq to control a much smaller population. America has 140,000 troops there now, and is considering withdrawing them. The Saudis are considering seriously funding the Sunni insurgents if the Iranians continue to fund the Shiites.
The Iraqi constitution was designed to allow the oil to be divided fairly between Sunni, Shiites and Kurds. If it comes to partition the Sunni will be the losers as there is little oil in the Sunni areas.
Although I doubt that the numbers of Iraqi dead are anything like the 600,000 estimated in the Lancet article, the numbers of Iraqis killing each other has grown and is growing.
Europe went through all this in the seventeenth century. Does no-one learn from other people's mistakes?