The Defense Intelligence Agency (or DIA) was a pre-War government agency of the United States. It has a field office in Point Lookout's Naval recruiting center that was investigating reports of a Chinese sympathizer in the vicinity named Wan Yang.
A Defense Intelligence Agency facility called "Switchboard" was established below a Slocum's Joe shop near Boston, where they developed an advanced robot by the name of Predictive Analytic Machine. The facility was repurposed into the headquarters of the Railroad until the Institute attacked and put the facility out of action. Further Railroad missions have the Sole Survivor seek caches left around the Commonwealth by the DIA.