The Workers’ and Peasants’ Red Army started out as the Soviet Union’s revolutionary communist combat groups during the Russian Civil War of 1918-1922. It grew into the national army of the Soviet Union. By the 1930s the Red Army was among the largest armies in history.
The “Red Army” name refers to the traditional colour of the workers’ movement. On 25 February 1946 (when Soviet national symbols replaced revolutionary symbols), the Red Army was renamed the Soviet Army (Советская Армия, Sovetskaya Armiya).
The Red Army is widely credited with being the decisive force in the Allied victory in the European Theatre of World War II, having engaged and defeated about 80% of the German armed forces, the Wehrmacht and much of the Waffen SS on the Eastern Front. (Wikipedia)