The Nazi Party:
The Geheime Staatspolizei (German for Secret State Police, abbreviated “Gestapo”) was the secret police of Nazi Germany, and its main tool of oppression and destruction, which persecuted Germans, opponents of the regime, and Jews. It later played a central role in helping carry out the Nazi's "Final Solution."
The Gestapo was formally organized after the Nazis seized power in 1933. Hermann Göring, the Prussian minister of the interior, detached the espionage and political units of the Prussian police and proceeded to staff them with thousands of Nazis. On April 26, 1933, Göring became the commander of this new force that was given power to shadow, arrest, interrogate, and intern any "enemies" of the state. At the same time that Goring was organzing the Gestapo, Heinrich Himmler was directing the SS (Schutzstaffel, German for “Protective Echelon”), Hitler's elite paramilitary corps. In April 1936, he was given command of the Gestapo as well, integrating all of Germany's police units under Himmler.
Later in 1936, the Gestapo was merged with the Kriminalpolizei (or “Kripo,” German for Criminal Police). The newly integrated unit was the called the Sicherheitspolizei (or “Sipo,” German for Secret Police). In 1939, during the reorganization of the German armies, the Sipo was joined with an intelligence branch of the military known as the Sicherheitsdienst (“SD,” meaning Security Service). After this merger, the Sipo became known as the Reichssicherheitshauptamt (“RSHA,” meaning Reich Security Central Office), and was headed by Reinhard Heydrich. Because of these frequent changes, the functions of the Gestapo became blurred, and often overlapped with those of the other branches of the German forces.
During World War II, the Einsatzgruppen ("Task Force", mobile killing squads) was formed, and came to be an integral part of the Gestapo. It was the Einsatzgruppen's job to round up all the Jews and other “undesirables” living within Germany's newly conquered territories, and to either send them to concentration camps or put them to death.
At the end of 1940, when the Jews in Eastern Europe were interned in ghettos, the Gestapo was charged with guarding and supervising the ghettos, imposing forced labor, and causing starvation and disease in an effort to decimate the ghetto inhabitants. After the invasion of Russia in 1941, the decision was made to kill all the Jews of Europe in gas chambers and the Gestapo was called upon to supervise the dispatch of the Jews to the camps specially adapted or constructed for the program of mass murder.
The Gestapo units excelled in their unabated and premeditated cruelty, in their ability to delude its intended victims as to the fate that awaited them, and in the use of barbaric threats and torture to lead the victims to their death, all as part of the "Final Solution." The units were taught many torture techniques, and were also taught many of the practices that German doctors in Dachau tested on the inmates of concentration camps. During its tenure, the Gestapo operated without any restrictions from the civil authority, meaning that its members could not be tried for any of their police practices. This unconditional authority added an elitist element to the Gestapo; its members knew that whatever actions they took, no consequences would arise.
After the war, very few of the important members of the Gestapo were caught and brought to trial.