It might be time for a 'time out' in Iraq
It seems to me that we and the people of Iraq could benefit from a new approach there. Instead of trying to force at least three major tribes who hate one another to share the land, it might be wiser to split the land into three new sovereign states, one each for the Kurds, Sunnis, and Shiites.
Accord each a fair share of the oil resources in Iraq. If necessary partition Baghdad into two halfs, between the Sunnis and Shiites.
It has been proven over and over again that an effective way to stop fighting between tribes - or if you are a parent dealing with kids - is to separate them. They will continue to fight if they are not separated and, if they believe it is in their best selfish interest, to keep fighting seeking an advantage. When we separate kids and enforce time-outs on them it usually stops the fighting.
Let's do the same in Iraq.
It could be a win-win for everyone involved. It would allow like tribes to have their own sovereign state with the government of their choice instead of trying to make one size and type of government fit all three tribes. Separation would stop much of the sectarian fighting.
The U.S. forces would no longer be responsible for acting like a police force for all of Iraq. Instead they would be responsible only for maintaining the boundaries between the three states, presumably allowing a drawdown of US troops much earlier than if we continue our present policy.
Tri-parting Iraq would provide a stable income to each of the three states, allowing them to spend their income as they choose. Each state would be free to decide for itself without the need to seek approval from members of two other tribes for either the amount of the expense or for approval of what to spend it on.
The three-state idea might be worth at least a try. I doubt it would be worse than the present situation there.