Simple.
We take the oil fields, for the USA, fence em in.
Start pumping cheap oil for use here in the USA. Then we sell the Sunnis and the Shiaas weapons, all they want as long as they are made here in the good ole USA by american workers.
Then we sit back and enjoy the oil while we laugh as we watch them kill each other.
Thats my plan for Iraq.
If the Iranians or the Saudis dont like it, we take their oil fields too, and sell them weapons to kill each other with.
If they ask us nice we establish the PAX Romana for them, and give them a small cut of the oil profits. Putin, can stomp his feet and pee his KGB issued panties.
Thats my solution
who's gonna guard the oil fields? whoever is guarding the oil fields bwill be attacked daily just like Iraq.