Matthais Kleinheisterkamp served in various units in World War I, and was awarded both classes of the Iron Cross. After the war he served in both the infantry and the cavalry until he joined the SS in 1934. He transferred to the SS/VT in 1938. Kleinheisterkamp was assigned to the SS-F�hrerschule Braunschweig as an infantry instructor. He taught there for one year, after which he joined Hausser's Inpectorate as a senior staff officer. On December 1st, 1938 he became commander of III/Deutschland, where he remained until the summer of 1940. In June 1940 he transferred to "Totenkopf" and became Infanterie Regiment 3 Commander. After this posting Kleinheisterkamp was transferred to take Bittrich's place as DR commander, during which time he was awarded the Knight's Cross. After DR he held various senior postings, finally ending up as XI.SS-Armee-Korps Commander.