The Reichswehr (German for "Imperial Defence") formed the military organization of Germany from 1919 until 1935, when it was renamed the Wehrmacht ("Defence Force").

At the end of World War I, the forces of the German Empire had mostly split up, the men making their way home individually or in small groups. Many of them joined the Freikorps ("Free Corps"), a collection of volunteer paramilitary units that were involved in revolution and border clashes between 1918 and 1923.

The newly formed Weimar Republic did need a military though, and on 6 March 1919 a decree established the Vorläufige Reichswehr ("Provisional National Defence"), consisting of a Vorläufige Reichsheer ("Provisional National Army") and a Vorläufige Reichsmarine ("Provisional National Navy"). On 30 September 1919, the army was reorganized as the Übergangsheer ("Transitional Army"). About 400,000 men served in the armed forces. This lasted until 1 January 1921, when the Reichswehr was officially established according to the limitations imposed by the Treaty of Versailles (Articles 159 to 213).

Adolf Hitler (German: [ˈadɔlf ˈhɪtlɐ] ( listen); 20 April 1889 – 30 April 1945) was an Austrian-born German politician and the leader of the National Socialist German Workers Party (German: Nationalsozialistische Deutsche Arbeiterpartei (NSDAP), commonly referred to as the Nazi Party). He was chancellor of Germany from 1933 to 1945 and dictator of Nazi Germany (as Führer und Reichskanzler) from 1934 to 1945. Hitler is commonly associated with the rise of fascism in Europe, World War II, and the Holocaust.

A decorated veteran of World War I, Hitler joined the German Workers' Party, precursor of the Nazi Party, in 1919, and became leader of the NSDAP in 1921. In 1923, he attempted a coup d'état, known as the Beer Hall Putsch, in Munich. The failed coup resulted in Hitler's imprisonment, during which time he wrote his memoir, Mein Kampf (My Struggle). After his release in 1924, Hitler gained popular support by attacking the Treaty of Versailles and promoting Pan-Germanism, antisemitism, and anticommunism with charismatic oratory and Nazi propaganda. After his appointment as chancellor in 1933, he transformed the Weimar Republic into the Third Reich, a single-party dictatorship based on the totalitarian and autocratic ideology of Nazism. His aim was to establish a New Order of absolute Nazi German hegemony in continental Europe.