In September 1939, the 51st became part of the Ukrainian Front for the Soviet invasion of Poland, but did not see combat. The division fought in the Winter War as part of the 7th Army from January to April 1940. Five soldiers of the division were awarded the title Hero of the Soviet Union for their actions during the war. In June 1940, the division participated in the Soviet occupation of Bessarabia as part of the 14th Rifle Corps.On 22 June 1941, the division was part of the 14th Rifle Corps of the 9th Army in the Odessa Military District. The division was based in the Danube Delta area. It fought against advancing German troops in Operation München. It retreated back to the Prut and then the Dniester near Dubăsari. The division then was forced to retreat back to the Southern Bug and the Dnieper at Kakhovka and Kherson. By November 1941, the division was in the Donbass. On 16 November, the division, now part of the 37th Army, attacked in the direction of Pavlovka and Taganrog. On 27 November, the division participated in the Battle of Rostov. The division did not break through until 29 November and advanced to Sultan-Saly. In January 1942, the division transferred to fight in the Barvenkovo-Lozovaya Operation and was on the Donets. In late July, the division was withdrawn on the Don and across the Manych. It was disbanded on 16 August and its personnel transferred to other units.