After the Riga Peace Treaty, on September 2, 1921, Mieczysław Smorawiński was assigned to the 2nd Legions Infantry Division as the commander of infantry of that unit. He served at that post until March 20, 1927. Simultaneously, he graduated from the Centre for Infantry Training in Rembertów and was promoted to colonel. During the May Coup d'État of 1926, Smorawiński led a small troop of his men from Kielce in support of Józef Piłsudski's forces fighting in Warsaw. On March 19, 1927, he was assigned to the Kraków-based 6th Infantry Division as its commander. On January 1, 1928, he was promoted to the rank of Brigadier General and became the youngest General in Polish service until then. In October 1932 he was assigned to the Grodno-based Corps Area Command No. III as the deputy commander. After his successful training there, in October 1934 he became the commander of the Lublin-based Corps Area Command No. II.