The Pentagon might need to spend billions to overcome the damage done to military security by Edward Snowden’s release of classified intelligence documents, the chairman of the Joint Chiefs of Staff told Congress on Thursday.

And it might take two years to determine the extent of that damage, Army Gen. Martin Dempsey told a House Armed Services Committee hearing on the defense budget.

“The vast majority of the documents that Snowden – Mr. Snowden – exfiltrated from our highest levels of security, the vast majority had nothing to do with exposing government oversight of domestic activities,” Dempsey said in response to a question from Rep. Mac Thornberry, R-Texas. “The vast majority of those were related to our military capabilities, operations, tactics, techniques and procedures.”