In 1924, Friedrich von Mellenthin enlisted in the Reichsheer; in 1932 he married Ingeborg von Aulock. He was assigned to the Prussian Military Academy in 1935. Between 1937 and June 1941, Mellenthin held several general staff positions in the Army; in June 1941, Mellenthin was posted to North Africa, where he served as a staff officer in the Afrika Corps until September 1942.