During
World War II, Lemm served in the
Wehrmacht and was a recipient of the
Knight's Cross of the Iron Cross with Oak Leaves and Swords. He was promoted to Major 1943, 1944 and Oberst 1945. Lemm joined the in 1957 and commanded the 7th Panzergrenadier-Brigade of the
3rd Panzer-Division in
Hamburg until 1963, when he was promoted to
Brigadegeneral. In 1970 he was promoted to
Generalmajor and commanded the 5th Panzer-Division in
Diez. Promoted further in 1974, he was named Chief of the Troop Office of the , with the rank of . He was awarded the
Great Cross of Merit with Star and the
Legion of Merit; he retired in 1979. After this he became honorary president (
Ehrenpräsident) of the
Association of Knight's Cross Recipients. ==Awards==