In recent weeks, U.S.-backed ground forces have sent an estimated 30 terabytes of data — equal to nearly two years of nonstop video footage — to the National Media Exploitation Center in Bethesda, Md., a little-known arm of the Pentagon’s Defense Intelligence Agency, according to officials who spoke on condition of anonymity to discuss the intelligence.

Analysts there are scrutinizing handwritten ledgers, computer spreadsheets, thumb drives, mobile phone memory cards and other materials for clues to terrorist cells or plots in Europe or elsewhere.

“The reason electronic exploitation is so critical is that enemy forces doesn’t fake those records,” an intelligence official said. “When you interrogate someone they can hide facts, but logs of phone calls and video clips don’t lie. That stuff isn’t made-up.”