[3] Following Germany's defeat in World War II, the tribunal at the Nuremberg trials officially declared that the SD was a criminal organisation, along with the rest of Heydrich's RSHA (including the Gestapo) both individually and as branches of the SS in the collective.

[5] The SD, one of the oldest security organizations of the SS, was first formed in 1931 as the Ic-Dienst (Intelligence Service[a]) operating out of a single apartment and reporting directly to Heinrich Himmler.

Even before Hitler became Chancellor in January 1933, the SD was a veritable "watchdog" over the SS and over members of the Nazi Party and played a critical role in consolidating political-police powers into the hands of Himmler and Heydrich.

On 28 February 1933, Hitler convinced Hindenburg to declare a state of emergency which suspended all civil liberties throughout Germany, due at least in part to the Reichstag fire on the previous night.

Hitler assured Hindenburg throughout that he was attempting to stabilize the tumultuous political scene in Germany by taking a "defensive measure against Communist acts of violence endangering the state".

[9] Wasting no time, Himmler set the SD in motion as they began creating an extensive card-index of the Nazi regime's political opponents, arresting labor organizers, socialists, Jewish leaders, journalists, and communists in the process, sending them to the newly established prison facility near Munich, Dachau.

[14] These events further extended Himmler's control of the security mechanism of the Reich, which by proxy also strengthened the surveillance power of Heydrich's SD, as both entities methodically infiltrated every police agency in Germany.

[23] Getting Mussolini to approve political intrigue against Austria was a major accomplishment, as the Italian Duce had expressed great concern previously in the wake of an Austrian SS unit's attempt to stage a coup not more than three weeks after the Röhm affair, an episode that embarrassed the SS, enraged Hitler, and ended in the assassination of Austrian Chancellor Engelbert Dollfuss on 25 July 1934.

[24] Nonetheless, to facilitate the incorporation of Austria into the greater Reich, the SD and Gestapo went to work arresting people immediately, using lists compiled by Heydrich.

Focusing on the Sudetenland with its 3 million ethnic Germans and the disharmony there which the Czech government could not seem to remedy, Hitler set Heydrich's SD in motion in what came to be known as "Case Green".

[31] Passed off as a mission to liberate Sudeten Germans from alleged Czech persecution, Case Green was in fact a contingency plan to outright invade and destroy the country, as Hitler intended to "wipe Czechoslovakia off the map.

The operation covered every conceivable type of intelligence data, using a myriad of cameras and photographic equipment, focusing efforts on important strategic locations like government buildings, police stations, postal services, public utilities, logistical routes, and above all, airfields.

[34] Hitler worked out a sophisticated plan to acquire the Sudetenland, including manipulating Slovak nationalists to vie for independence and the suppression of this movement by the Czech government.

Under directions from Heydrich, SD operative Alfred Naujocks was re-activated to engage in sabotage activities designed to incite a response from the Slovaks and the Czechs, a mission that ultimately failed.

[38] Eventually a diplomatic showdown pitting Hitler against the governments of Czechoslovakia, Great Britain, and France, whose tepid reaction to the Austrian Anschluss had precipitated this crisis to some degree, ensued.

[41][b] Aside from its participation in diminishing the power of the SA and its scheme to kill Röhm, the SD took part in international intrigue, first by activities in Austria, again in Czechoslovakia, and then by helping provoke the "reactive" war against Poland.

[42] The SD took concentration-camp inmates condemned to die, and fitted them with Polish Army uniforms which Heinz Jost had acquired from Admiral Wilhelm Canaris' Abwehr (military intelligence).

[44] Immediately in the wake of the staged incidents on 1 September 1939, Hitler proclaimed from the Reichstag in a famous radio address that German soldiers had been "returning" fire since 5:45 in the morning, setting the Second World War in Europe into motion.

[49] As part and parcel of its intelligence operations, the SD carefully tracked foreign opinion and criticism of Nazi policies, censoring when necessary and likewise publishing hostile political cartoons in the SS weekly magazine, Das Schwarze Korps.

These were monitored and reviewed by the head of the Inland-SD, Otto Ohlendorf (responsible for intelligence and security within Germany) and by the former Heidelberg professor and SD member Reinhard Höhn [de].

[48] Continued escalation of antisemitic policies in the spring of 1937 from the SD's Department of Jewish Affairs (German: Abteilung II/112: Juden) – staffed by members like Adolf Eichmann, Herbert Hagen, and Theodor Dannecker – led to the eventual removal (Entfernung) of Jews from Germany; regardless of concerns about where they were headed.

[62] On 27 September 1939, the SiPo became a part of the Reich Security Main Office (RSHA) under Heydrich:[63] From February 1944 forward, the sections of the Abwehr were incorporated into Amt VI.

[68] On 31 July 1941, Göring gave written authorisation to SD Chief Heydrich to ensure a government-wide cooperative effort in the implementation of the so-called Final Solution to the Jewish question in territories under German control.

The memo explicitly stated: The SD will, where possible, follow up immediately behind the troops as they move in and, as in the Reich, will assume responsibility for the security of political life.

[70]Correspondingly, SD affiliated units, including the Einsatzgruppen followed German troops into Austria, the Sudetenland, Bohemia, Moravia, Poland, Lithuania, as well as Russia.

[74] Nonetheless, by June 1941, the SS and the SD task forces were systematically shooting Jewish men of military age, which soon turned to "gunning down" old people, women, and children in the occupied areas.

[g] Whatever their original purpose, the SD and SS were ultimately created to identify and eradicate internal enemies of the State, as well as to pacify, subjugate, and exploit conquered territories and peoples.

[92][i] The SD-SiPo was the primary agency, in conjunction with the Ordnungspolizei, assigned to maintain order and security in the Nazi ghettos established by the Germans throughout occupied Eastern Europe.

[94] On 7 December 1941, the same day as the Japanese attack on Pearl Harbor, the first extermination camp was opened at Chelmno near Lodz by Ernst Damzog, the SD and SiPo commander in occupied Poznań (Posen).

[97] How extensive the SD's knowledge was about the early plots to kill Hitler by key members of the military remains a contested subject and a veritable unknown.