Galanin was drafted into the Red Army in 1919 and fought as an ordinary soldier in the Russian Civil War. He became an officer during the interwar period and graduated from the Frunze Military Academy. Galanin then served in several staff positions in the Transbaikal Military District and commanded the 57th Rifle Division during the Battles of Khalkhin Gol in 1939. He was promoted to command the 17th Rifle Corps in Ukraine in 1940, and held that position when Operation Barbarossa, the German invasion of the Soviet Union, began. After leading the corps in the Battle of Uman and the retreat east through Ukraine, he took command of the 12th Army and then the 59th Army. From August 1942 he was deputy command of the Voronezh Front, and in October he took command of the 24th Army, which he led in Operation Uranus. After leading the 70th Army in the Battle of Kursk, Galanin became command of the 4th Guards Army, which he led for the rest of the war, except for a brief period as commander of the 53rd Army. Postwar, he was made deputy commander of a rifle corps, and retired in 1946.