1914-1918. Called back to active duty when World War I started. He left Vienna in the summer of 1914 to go to war, on the same day and on the same train on which he had planned to leave to teach a seminar in Silesia. He served as a captain with the artillery in the Austro-Hungarian cavalry, primarily on the Eastern front in the Carpathian Mountains, Russian Ukraine, and Crimea. During the latter part of the war, he worked on economic problems with the Army's General Staff in Vienna. 1918-1919.Taught a class of officers seeking to return to civilian life at the Wiener Exportakademie [Viennese Export Academy], later the Hochschule für Welthandel [Institute for World Trade].
1918-1919.Taught a class of officers seeking to return to civilian life at the Wiener Exportakademie [Viennese Export Academy], later the Hochschule für Welthandel [Institute for World Trade].