Throughout the ISIS war, US officials have made it clear that one of the key goals of their war was to prevent the Islamists from exporting oil, a key source of revenue. Oil production in their territory is mostly run privately, through local groups, but officials insist ISIS is still, after a year of airstrikes, making $50 million monthly on the exports.

That’s the largest single source of revenue for the group, and continues in spite of the many attacks on the oil industry in northeast Syria, and despite the precipitous drop in the price of oil in the past year.

Officials say that ISIS is often selling the oil at a substantial discount to market prices, in some cases as low as $10 a barrel. The smugglers then get the oil out of the country, usually by way of major oil export hub Turkey, and sell it for a substantial profit.

The estimates on production are about 30,000 barrels per day in Syria, and 10,000 to 20,000 barrels per day in Iraq. The Iraqi production is largely not being exported by ISIS, but rather is being refined for internal use. The ISIS production in Iraq, interesting, is being run by the employees of Iraq’s state oil company who worked there before the fall of Mosul, and they are getting paid substantial rates by ISIS, up to $1,000 per day, to keep it flowing.