Hauptmann Otto Hartmann was a World War I flying ace credited with seven aerial victories. Otto Hartmann was born on 7 February 1889, in Nassau, Kingdom of Württemberg, the German Empire. He entered the Imperial German Army as a cadet on 5 March 1908. During his service to his country, Otto Hartmann was awarded both classes of the Iron Cross and the Kingdom of Württemberg's Medal of Military Merit.