Defense Investigative Service D-23AG

The Defense Investigative Service D-23AG was established in 1977 as a specialized counterintelligence and investigative unit within the Department of Defense. Tasked with conducting background checks, security clearance investigations, and counterintelligence operations, the unit played a crucial role during the Cold War in safeguarding sensitive military information. D-23AG became renowned for uncovering several espionage attempts against U.S. defense infrastructure throughout the 1980s and 1990s. In 2005, the unit’s functions were integrated into the newly formed Defense Counterintelligence and Security Agency, marking the end of its independent operations but cementing its legacy in military security history.