Born in 1896, Tröger entered the army of Imperial Germany in 1915 as a Fahnen-junker (officer cadet) and served as an engineer. After World War I, he remained in the military, serving in the Reichsheer. From 1935 he was in the Wehrmacht and was posted to the Office of Mobile Troops at the Oberkommando der Wehrmacht (Armed Forces High Command), commonly known as OKW, for two years from 1938.