U.S. airstrikes are damaging ISIS -- specifically, its oil business

Most of the group’s oil flows through local middlemen and is paid for almost entirely in cash, making transactions extremely difficult to track and shut down. This has insulated Islamic State from traditional methods the West has used to dry up terrorist funds in the past, such as international banking sanctions and anti-money laundering laws.

A straight-up bombing campaign does seem to be doing a lot of that work. According to the IEA report, U.S.-led sorties over northern Iraq and Syria are “frustrating the jihadists’ ability to operate oil fields and refineries.” At its peak, most of the oil smuggled from Iraq was loaded from the Ajeel oil field near Tikrit on tanker trucks and routed toward Kurdistan. The IEA, citing Iraqi oil industry sources, estimates that Islamic State was loading about 120 tanker trucks with about 20,000 barrels a day from Ajeel. Sustained airstrikes, including ones targeting convoys, have cut that traffic to about 10 trucks a day, or about 2,000 barrels, according to the IEA’s report.