National Security And The FBI Surveillance Of Enemy Aliens, 1940-1978
Custodial Detention Index
The Custodial Detention Index was a list of suspects and potential subversives, classified as “A”, “B” and “C”; the ones classified as “A” were destined to be immediately arrested and interned at the outbreak of war. The actual assignment of the categories was, however, based on the perceived individual commitment to the person’s native country, rather than the actual potential to cause harm.
Wartime Surveillance Efforts
When the United States entered the war, FBI agents aided national defense efforts by placing trained agents at key military and defense industry sites. Wartime agents received more intense training in counterintelligence measures, and the FBI established special counterintelligence units for covert operations at the government’s discretion. The FBI’s surveillance workload during World War II was enormous: over 1 million registered “enemy” aliens were living in the U.S.; many were nationals from Axis power nations awaiting citizenship.
Postwar Surveillance Efforts
When World War II ended in August 1945, increasingly hostile relations between the United States and the Soviet Union led to a diplomatic and military standoff that lasted over six decades. J. Edgar Hoover maintained a new list of possible subversives and enemies of the state, under the title of the Security List and, later Administrative List. The information included the same types as that collected for the former Custodial Detention Index.
Records of the Federal Bureau of Investigation, Department of Justice, Custodial Detention, Headquarters Library, Washington, D.C.