After completing his studies, he continued his military career in the Hussar Guard Regiment of the Prussian Army, becoming a captain and then squadron commander.He also continued as regent of Reuss-Greiz, because of a physical and mental disability of Prince Heinrich XXIV due to an accident in his childhood.[1] As a state of the German Empire, Heinrich XXVII saw his principality enter the First World War under Kaiser Wilhelm II on the side of the Central Powers.In exile, Heinrich became the honourary chairman of the Reuss Institute for Art and Public Welfare, to which the court theatre that he built was soon transferred.He was initially laid to rest in the castle's Chapel, but was then transferred to Schleiz and buried there on 26 November 1928 in his family's crypt in the Mountain Church of Saint Mary.