 From spring 1916, the British had deployed five tunnelling companies along the Vimy Ridge and during the first two months of their tenure of the area, 70 mines were fired, mostly by the Germans.Between October 1915 and April 1917 an estimated 150 French, British and German charges were fired in this sector of the Western Front.In May 1916, Operation Schleswig-Holstein, a German infantry attack, forced the British back , to stop British mining by capturing the shaft entrances.