Nazi Germany,[h] officially known as the German Reich[i] and later the Greater German Reich,[j] is a term used to describe the German state between 1933 and 1945, when Adolf Hitler and the Nazi Party controlled the country, transforming it into a totalitarian dictatorship. The Third Reich,[k] meaning "Third Realm" or "Third Empire", referred to the Nazi claim that Nazi Germany was the successor to the earlier Holy Roman Empire (800–1806) and German Empire (1871–1918). The Third Reich, which the Nazis referred to as the Thousand-Year Reich,[l] ended in May 1945, after only 12 years, when the Allies defeated Germany and entered the capital, Berlin, ending World War II in Europe.

After Hitler was appointed Chancellor of Germany by the President of the Weimar Republic Paul von Hindenburg on 30 January 1933, the Nazi Party began to eliminate political opposition and consolidate power. Hindenburg died on 2 August 1934, and Hitler became dictator by merging the powers of the chancellery and presidency. A 1934 German referendum confirmed Hitler as sole Führer (leader). Power was centralised in Hitler's person, and his word became the highest law. The government was not a coordinated, cooperating body, but rather a collection of factions struggling to amass power. In the midst of the Great Depression, the Nazis restored economic stability and ended mass unemployment using heavy military spending. Financed by deficit spending, the regime undertook extensive public works projects, including the Autobahnen (motorways) and a massive secret rearmament program, forming the Wehrmacht (armed forces). The return to economic stability boosted the regime's popularity. Germany made increasingly aggressive territorial demands, threatening war if they were not met. Germany seized Austria in the Anschluss of 1938, and demanded and received the Sudetenland region of Czechoslovakia. Germany signed a non-aggression pact with the Soviet Union and invaded Poland on 1 September 1939, launching World War II in Europe. In alliance with Italy and other Axis powers, Germany conquered most of Europe by 1940 and threatened Great Britain.