Clayton Donnell is retired from the US Air Force. He has a degree in history and has passionately studied military history and fortress engineering for thirty years. Clayton lived for many years in Europe and studied the architecture and archaeology of the most renowned fortress systems of Belgium, France and Germany. He created the first internet site in the world in English about the Maginot Line, and another on the fortress and Battle of Liege, Belgium. His publications include Modern European Military Fortifications, 1870-1950: A Selected Annotated Bibliography (edited with J.E. Kaufmann), The Forts of the Meuse in World War I, The German Fortress of Metz, Fortifications of Verdun 1874-1917 and Breaking the Fortress Line 1914.