Born in Jena in 1814 to a Saxon noble family, he entered the Saxon Army at the age of 17. In 1833 he transferred to the Austrian service. Gablenz fought in the First Italian War of Independence. Promoted to Major in the General-Staff-Corps he was transferred to Hungary to combat the Hungarian Revolution and was posted to the staff of FM Alfred I, Prince of Windisch-Grätz and then as the chief of staff to GdK Schlik's army corps. For his services in Hungary Gablenz was promoted to colonel in December 1849.