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).