5923008 ?Daybreak on Vimy Ridge! after our dogged and impetuous assault on the height, April 9th 1917? (b/w photo) by Unknown photographer, (20th century); National Army Museum, London; (add.info.: ?Daybreak on Vimy Ridge! after our dogged and impetuous assault on the height, April 9th 1917?. Photograph, World War One, Western Front (1914-1918), 1917. On 9 April 1917, four divisions of Canadian infantry recaptured the four-mile long strategic height of Vimy Ridge as part of the Battle of Arras (1917). Vimy Ridge had been occupied by the Germans since October 1914. Fortified, it commanded the flat countryside for miles around. Its capture would ensure that the southern flank of the Arras offensive could advance without suffering German enfilade fire. Careful preparations by the Canadians helped to make the assault a brilliantly successful one, forcing a German withdrawal and pressing forward the Allied front line. Vimy Ridge was the first occasion when all four divisions of the Canadian Expeditionary Force fought together. It thus became an important symbol of national unity in much the same way as Gallipoli (1915) was for the ANZACs. From a collection of 101 stereoscopic photographs entitled ?The Great War?.); by National Army Museum ; out of copyright.