Career
He entered the army as an Offizieranwärter (Officer candidate) in the signals troops in April 1963. In early 2003 he was appointed the commander of the International Security Assistance Force. On August 11, 2003, control of ISAF was handed to North Atlantic Treaty Organization with Van Heyst being replaced by Lieutenant General Goetz Gliemeroth, also of Germany.
Van Heyst retired on 1 July 2005.