World War I: At Home
Modern military intelligence had its beginnings in World War I when many of the intelligence disciplines still in use today were deployed for the first time: aerial photography, signals intercept, interrogation teams, and counterintelligence agents.

Army Intelligence within the continental United States and intelligence in support of the forces overseas developed along two separate tracks. On the home front, COL Ralph Van Deman, Chief of the Military Intelligence Division of the War Department General Staff, directed much of his attention to the new field of negative intelligence, or counterintelligence. The Army was concerned about a possible threat from German spies and saboteurs. Van Deman used the newly created Corps of Intelligence Police to conduct undercover investigations of individuals and organizations. He was equally concerned about the loyalty of recent immigrants being drafted into service. Van Deman feared that the newly forming National Guard and National Army divisions might become “infested” with German agents and sympathizers. To protect the force, two soldiers within each company were appointed to secretly report on any suspicious activity, using the guidelines contained in a confidential pamphlet, “Provisional Counter-Espionage Instructions”.