Jaklicz was born on 17 September 1894 in Kraków. After graduation from high school, he studied philosophy at the Jagiellonian University, and was active member of the Polish Sokol movement. In August 1914, Jaklicz joined 3rd Infantry Regiment of the Polish Legions. Promoted to the rank of company commander, he fought in Eastern Carpathians, Bessarabia and Volhynia. Following the creation of the Polish Auxiliary Corps, Jaklicz became a staff officer, and after its dissolution, he joined Polska Siła Zbrojna (Polnische Wehrmacht).
