As early as September 1931, after the Japanese invasion of Manchuria, US officials began to compile lists of individuals, lists which were particularly focused on the Issei. This data was eventually included in the Custodial Detention index (CDI). Agents in the Department of Justice's Special Defense Unit classified the subjects into three groups: A, B, and C, with A being the "most dangerous", and C being "possibly dangerous".
As early as ,September 1931, after the Japanese invasion of Manchuria US officials began to compile lists of individuals, lists which were particularly focused on ,the Issei. This data was eventually included in the Custodial Detention index (CDI). Agents in the Department of Justice's Special Defense Unit classified the subjects into three groups: A, B, and C, with A being the "most dangerous" and C being "possibly dangerous".