This study explores the organization, history and uniforms of the Soviet Red Army during the 20 years between its victory in the Civil War and the invasion of the USSR by Germany in 1941. The two decades following the Bolshevik victory over the 'Whites' in the Russian Civil War saw widespread and fundamental developments for the Red Army. Nevertheless, these still left it largely unready to face Germany’s Operation Barbarossa in June 1941. Having been reduced in size and planning for modernization, the Red Army of the 1920s was employed to ruthlessly crush anti-Bolshevik opposition (real or suspected) in several regions of the USSR, notably Ukraine and Central Asia, and to fight a brief border war against Chinese Manchuria. During the 1930s, Stalin virtually 'beheaded' the army by a needless series of murderous purges of the officer class; despite this, the Red Army was victorious in clashes against Imperial Japan in the Nomonhan region in 1938–39, where General Zhukov earned his spurs. Simultaneously, the Soviet Union sent instructors and pilots to fight for the Republicans in the Spanish Civil War (1936–39). The non-aggression pact with Nazi Germany allowed Stalin to take over half of Poland in September 1939; but a few months later his 'Winter War' against Finland demonstrated serious inadequacies in the Red Army's readiness for modern warfare, which would be shockingly confirmed in the first days of Operation Barbarossa. Using rare photos and detailed colour artwork, this study explores the interwar history of the Red Army, describing its campaigns, organization and uniforms, and focusing on the 20 years between its victory in the Civil War and the invasion of the USSR by Germany in 1941.