Oil has helped fund and fuel the self-declared Islamic State in Iraq and Syria, with small amounts coming from fields in northern Iraq and being smuggled across the borders in tanker trucks.
A tiny drop in the sea of petroleum globally, the oil tapped by Daesh has given it a revenue source most extremist groups lack, according to the Washington Post.
But the oil installations and tanker trucks could be targets for the U.S.-led coalition that hopes to cripple the self-proclaimed caliphate. And the poor quality of crude oil in northern Iraqi fields and the steep cost of smuggling probably limited earnings to $1 million a day over the summer, according to oil industry sources.