Mata Hari was the stage name of Margaretha Geertruida (Grietje) Zelle (7 August, 1876, Leeuwarden, The Netherlands – 15 October, 1917, Vincennes, France). She was a Dutch-Frisian exotic dancer. She was executed by a firing squad of the French Army. People at the time thought she was a spy during World War I and because she had relationships with both German and French officers, they thought she was a double agent. Her dossier is to be released in 2017 (a hundred years after her death).