WASHINGTON (Reuters) - Since last month, U.S. warplanes have struck Islamic State's oil infrastructure in Syria in a stepped-up campaign of economic warfare that the United States estimates has cut the group's black-market earnings from oil by about a third.
In finding their targets, U.S. military planners have relied in part on an unconventional source of intelligence: access to banking records that provide insight into which refineries and oil pumps are generating cash for the extremist group, current and former officials say.