Nazi Germany and the Third Reich are the common English names for Germany under the government of Adolf Hitler and the National Socialist German Worker's Party (NSDAP), from 1933 to 1945. Third Reich (Drittes Reich) denotes the Nazi State as the historical successor to the mediæval Holy Roman Empire (962–1806) and to the modern German Empire (1871–1918). Nazi Germany had two official names, the Deutsches Reich (German Reich), from 1933 to 1943, when it became Großdeutsches Reich (Greater German Reich).

On 30 January 1933, Adolf Hitler was appointed Chancellor of Germany, and, although he initially headed a coalition government, he quickly eliminated his government partners. In 1933, the German national borders still were those established in the peace Treaty of Versailles (1919), between Germany and the Allied Powers (United Kingdom, France, the United States, Italy, Japan et alii.) at the end of the First World War (1914–18); to the north, Germany was bounded by the North Sea, Denmark, and the Baltic Sea; to the east, it was divided into two and bordered Lithuania, the Free City of Danzig, Poland, and Czechoslovakia; to the south, it bordered Austria and Switzerland, and to the west, it touched France, Luxembourg, Belgium, the Netherlands, the Rhineland, and the Saarland. Those borders changed with Germany’s regained control of the Rhineland, the Saarland, the Memelland, and annexed Austria, the (Czech) Sudetenland and Bohemia and Moravia. Germany expanded into Greater Germany during the Second World War, begun 1 September 1939, with the German invasion of Poland, triggering the United Kingdom and France to declare war on Nazi Germany.

During the war, Germany conquered and occupied most of Europe and Northern Africa. The Nazis persecuted and murdered millions of Jews and other minorities in the Holocaust Final Solution. Despite an alliance with other nations, mainly Italy and Japan, the Axis, by 1945, Germany had been defeated and occupied by the Allied powers, the Soviet Union, UK, US, Canada, and France.

Law enforcement in Germany is constitutionally solely vested in the states, which is one of the main features of the German political system. Therefore, unlike France, Italy, the United States, Canada or many other countries, Germany has no federal police force comparable to the Carabinieri, Police Nationale, FBI or RCMP. Police has always been a responsibility of the German states and was continued after 1871 when the country was unified. The constitution of the Weimar Republic 1919 eventually did provide for the possibility to create a national police force, should the necessity arise, but it was only in the Nazi era, that a national secret police force (Gestapo) was created and the state police forces were unified under a central leadership. The police became a tool of the centralized state and the Nazi party. Following the defeat of 1945, Germany was divided; in 1949 the three western zones were turned into the Federal Republic of Germany (West Germany), the eastern zone became the German Democratic Republic (East Germany). Each country pursued a different path concerning law enforcement.

In light of the gross misuse of power by the centralized Nazi state the new constitution of the West Germany provided for a strict separation of powers, placing law enforcement firmly into the hands of the states. The only policing allowed on the federal level was border control (Bundesgrenzschutz including coast guard), controlled by the Ministry of Interior and originally organized along paramilitary lines, the Federal Criminal Police Office and the Police of the parliament.

East Germany created a new centralized police force under the Ministry of Interior, the paramilitary Volkspolizei. It also established a border police, initially an independent force, then integrated into the army and then reorganized as an independent military organization.