During the Polish-Bolshevik War Smorawiński distinguished himself as a commander of the 4th Legions Infantry Regiment in the ranks of the Polish 2nd Legions Infantry Division (November 10, 1919 to August 4, 1920. During the Polish retreat following a successful Bolshevik offensive in Belarus, Smorawiński was promoted to the rank of lieutenant colonel and assigned to the 4th Legions Infantry Brigade as its commanding officer. In the ranks of his unit he fought in the Battle of Warsaw. Following the Bolshevik defeat, his unit continued the pursuit after the fleeing Russians, finally liberating the town of Hrubieszów. After that his unit took part in the Battle of the Niemen River and reached Lida by the end of hostilities.