The Nord pas de Calais was one of the main theaters of the conflict, with many battles occurring between 1914 and 1918, including the Battle of Vimy Ridge assault during the Battle of Arras (1917), the Battle of Artois, Battle of Loos and the Battle of Cambrai. By the time the region was finally liberated by the Canadian Expeditionary Forces, the entire country was devastated and Arras had been 90% destroyed. Currently, there are 650 military cemeteries throughout the Nord-Pas-de Calais, mostly British and Canadian, as well as large memorials such as the Canadian National Vimy Memorial and Notre Dame de Lorette, the world's largest French military cemetery.