ISIS Empire: Smuggling, shakedowns, donations feed swelling terror budget

As the Islamic State seeks to export its brand of barbaric terror to would-be affiliates, the U.S. faces a growing challenge to find the sources of ISIS funding and blunt its flow to allied militants.

The terror army's most recent atrocity was the mass beheading of 21 Coptic Christians in Libya. It remains unclear how closely tied those militants are to ISIS in Iraq and Syria, but the Islamic State's underground economy continues to thrive. Even as the U.S.-led coalition strikes at what was long the heart of ISIS'...