Trump on the stump: A closer look at The Donald's proposed policies

Donald Trump clearly connects oil and foreign policy in the Middle East.

"I say that you can defeat ISIS by taking their wealth," Trump told Bill O'Reilly. "Take back the oil. Once you go over and take back that oil, they have nothing. You bomb the hell out of them, and then you encircle it, and then you go in. And you let Mobil go in, and you let our great oil companies go in. Once you take that oil, they have nothing left."

But taking over ISIS's oil supplies would almost certainly require more troops. Obama recently announced plans to send 450 troops to Iraq to aid Iraqi Security Forces in fighting ISIS, adding to the 3,050 U.S. personnel already there. But there's a lack of political appetite in Washington to send thousands of soldiers back to the country. (CNN, Eugene Scott)

Also, see our look at Exporting oil to gain influence.