The FBI uses this classification for investigations of individuals alleged to have unlawfully obtained information affecting national defense or unlawfully disclosed such information to a foreign government. The FBI's investigative jurisdiction in this area rests on both legislation, beginning with the Espionage Act of 1917, and presidential directives, notably two World War II era directives, promulgated in 1939 and 1943, which assigned to the FBI primary responsibility for investigating espionage and subversion. This is one of the oldest FBI classifications as it predates 1924. It is included in Director Hoover's July 28, 1924, memorandum on filing, but interestingly, in this memorandum, it is titled "Japanese Activities." Classification 65 remained relatively inactive until the World War II period. Between 1939 and 1945, it became extremely active, and, in fact, the bulk of the cases opened at Headquarters date from this period. Most of the cases opened during the World War II era did not deal with espionage; rather, most of these files delt with individuals suspected of Axis sympathies. However, classification 65 was used for the Bureau's major World War II espionage investigations, which, of course, concentrated on Axis operatives. After the war, the FBI shifted its emphasis in these investigations to those suspected of acting on behalf of Eastern Bloc nations, particularly the Soviet Union. While many of the postwar files deal with relatively minor investigations in which no espionage involvement was proven, it is in classification 65 that major espionage investigations are to be found, including the Rosenberg, Hiss, and Silvermaster cases. Since the 1970s, classification 65 also has been used for investigations of the unauthorized disclosure of security classified information.
