Edward Snowden is best known for exposing government surveillance, but "the vast majority" of the roughly 1.7 million documents Snowden took addressed top-secret military capabilities, operations, and tactics, according to the nation's highest-ranking military officer.
The cost of changing those tactics and coping with the security breach could total billions of dollars, Chairman of the Joint Chiefs of Staff Martin Dempsey told the House Armed Services Committee on Thursday.
Related: Three Reasons Snowden Can't Stop the NSA
Defense Department officials, along with officials from other agencies, are still investigating the documents Snowden took and determining how to blunt the risks they pose to U.S. security, Dempsey said.
"The mitigation task force will need to function for about two years—that's the magnitude of this challenge," Dempsey said. "I suspect it could cost billions of dollars to overcome the loss of security that has been imposed on us."
Dempsey's comments add to a chorus of congressional critics, such as House Intelligence Committee Chairman Mike Rogers, who have decried the potential costs of reversing the security damage after Snowden's leaks. Concerned lawmakers have also suggested that Russia, where Snowden remains under temporary asylum, may have gained access to his document trove.
This article originally appeared in NextGov.com.