Reichswehr (literally, "National Defense") was the name of the German armed forces from 1921 until 1935, when Hitler changed the name to Wehrmacht.

Replacing the Übergangsheer ("Transitional Army"), the Reichswehr came into existence in 1921 in accordance with the Treaty of Versailles, which strictly limited the character of the German armed forces, limiting the total number of personnel to a mere 100,000 men. The Reichsweir consisted of two forces - the Reichsheer, an army consisting of two seven infantry divisions and three cavalry divisions, and the Reichsmarine, a navy limited to only 15,000 men and a handful of tiny ships. Conscription of any kind and any air force whatsoever were completely proscribed by the treaty, as were large weaponry of any kind, including tanks, submarines, battleships, and modern artillery.

The Reichswehr was miniscule for a country of 70 million people, and was considered not even adequate to hold one of Germany's three major borders by the doctrines of the time. To insure that the Germans complied with the treaty restrictions, an Inter-Allied Military Control Commission kept careful watch over all aspects of German military activity. Nevertheless, the Reichswehr, under the capable command of Obergeneral Hans von Seekt, did all it could to prepare for a future return to glory. Think tanks and R&D units were concealed within civilian ministries, naval and airforce personnel were secretly trained abroad, and development proceeded on new military doctrines that would ultimately result in the "blitzkrieg" style of fast, coordinated, motorized warfare that swept across Europe in 1939-40.

After Adolf Hitler came to power in 1933, the secret expansion of the Reichswehr increased dramatically (by this time, the Allied Control Comission had been voluntarily withdrawn by the British and French as a foolhardy gesture of good faith). Finally in 1935, Hitler felt powerful enough to abandon all pretense, openly declaring national conscription and renaming the Reichswehr as the Wehrmacht ("Defense Power").