In late 1918, Jaklicz entered the Polish Army, and was named commandant of a battalion of the 36th Academic Legion Infantry Regiment, which fought in the Battle of Lemberg (1918). After serving briefly under Colonel Władysław Sikorski, in March 1919, he was transferred to the staff of 9th Infantry Division, where he remained until December 1919. From 2 January until 15 April 1920 Jaklicz attended a military course at the College of Polish General Staff. During the Polish–Soviet War, he was chief of staff of 15th Infantry Division, and then commandant of 25th Infantry Regiment. In late 1920, Jaklicz went to France, to study at Ecole Militaire.