 Complete the following phrase:  Drafted into the Imperial Russian Army just before World War I, Nikitin fought in the war as a non-commissioned officer with a Cossack cavalry regiment. Joining the Red Army during the Russian Civil War, he served as an assistant regimental commander with a division of the 1st Cavalry Army. Nikitin commanded a cavalry regiment during the 1920s and rose to cavalry division command in the 1930s. At the outbreak of Operation Barbarossa, he commanded the 20th Mechanized Corps in Belarus. After his unit suffered heavy losses during the Battle of BiałystokMinsk, Nikitin was wounded and evacuated during the 