The two memos below are evidence that the Office of Naval Intelligence (ONI) was conducting counterintelligence investigations, including physical surveillance of investigative subjects and personnel security (background) investigations on communications specialists during World War I. The third element of the NIS mission (criminal investigations) was not formalized until 1945.
Early evidence of ONI conducting counterintelligence investigations September 17, 1918
Early evidence of ONI conducting personnel security (background) investigations October 26, 1918