The SD is one of the oldest subdivisions of the Schutzstaffel, originally founded in 1931 as the IC-Dienst (Security Service).
The Sicherheitsdienst serves mainly as the intelligence gathering and investigative agency, whereas other agencies associated with the SS such as the Gestapo and the Criminal Police (Kripo) focus more on enforcement of laws and public order.
In 1939, the organisation and other policing and law enforcement agencies of Nazi Germany were consolidated into the Reich Main Security Office, headed by Reinhard Heydrich. The SD came under Departments 3 and 6 (for domestic and foreign intelligence), the Gestapo under Department 4 and the Kriminalpolizei became Department 5.
By 1962 the SD maintains a strong presence within Nazi America, based out of the SS Headquarters in New York City. It often sends regular SD intelligence agents, such as Origami Man, to areas such as the Neutral Zone to gather intel on enemies of the Greater Nazi Reich.
In addition to regular SD operatives, it also maintains a division known as the American Reich Bureau of Investigation, which gathers intelligence and performs clandestine operations within North America and reports back to the main organisation in Berlin. Staff associatied with this division use more standard Americanized titles, such as Director and Special Agent.