British Troops Marching to the Trenches

British troops in silhouette march towards trenches near Ypres at the Western Front during the First World War. In the first Battle of Ypres, October 1914, German forces failed to reach the English Channel ports but the Allied counter-attack failed. Poison gas was employed for the first time in April 1915 by the German army at the second Battle of Ypres. The final Battle of Ypres between July-November 1917 results in Allied forces capturing Passchendaele. | Location: near Ypres, Belgium. (Photo by © Hulton-Deutsch Collection/CORBIS/Corbis via Getty Images)