The 21st Rifle Division (; Military Unit Number 17752) was an infantry division of the Russian Soviet Federative Socialist Republic and then the Soviet Union's Red Army, active between 1918 and 1945. Formed in late 1918 during the Russian Civil War as the 5th Ural Infantry Division, the division fought on the Eastern Front. In September 1919 it was split up and two of its brigades and its headquarters transferred west. The division was reunited on the Southern Front in January, fighting in the final stages of the campaign there. In May it was transferred to fight in the Polish–Soviet War, and was one of the divisions that fought in the Battle of Radzymin during the larger Battle of Warsaw. After the Red Army was defeated by a Polish counterattack, the division retreated into Belarus. It transferred east again to suppress a peasant revolt in Western Siberia, and remained there until 1929, when it transferred to the Soviet Far East to fight in the Sino-Soviet conflict of that year. After Operation Barbarossa began on June 22, 1941, the division was sent west in September and fought in the Continuation War against Finland in Karelia. From the spring of 1944 it fought in the Arctic sector, initially in the area of Alakurtti. After the withdrawal of Finland from the war, the division was transferred to Hungary in January 1945. It fought in the end of the Budapest Offensive, Operation Spring Awakening, and the Vienna Offensive at the end of the war. Postwar, the 21st was withdrawn to Romania and converted into the 20th Mechanized Division, which was disbanded in 1947. Russian Civil War and Polish-Soviet War The 5th Ural Infantry Division was organised during the Russian Civil War on September 3, 1918, out of several smaller partisan detachments in Birsky Uyezd of Perm Governorate. Soon it was reinforced with a single artillery battery from Sankt Petersburg and two Workers' Brigades from the Arkhangelsk Front. The division fought in the Eastern Front of the Russian Civil War against the White Army led by Alexander Kolchak. It was part of the 3rd Army and fought in battles around Osa during the defence of Perm from November 29 to January 6, 1919. Transferred to the 2nd Army in January, it defended the Kama area in battles on the Kungur direction in the Osa area from January to March. During the Spring Offensive of the