In April 1917, Vimy Ridge (just north of Arras) had been held by the Germans since October 1914. Hill 145, at 61 metres, was the highest spot on the 14 kilometre ridge - itself but a small part of the 1,000 kilometre long Western Front. As well as being a military objective, the ridge overlooked the Douai Plain, an industrial area of coal mines and related factories.
To shield supplies and to provide shelter for attacking troops (and returning casualties), a series of 12 tunnels had been excavated by the Allied forces from behind the front line stretching forward into no-mans land. The front lines were comparatively lightly manned and much of the enemy shelling was concentrated on the main and reserve lines. The tunnels totalled five kilometres in length and were supplied with both electricity and water. Dug in chalk, the spoil was disposed off by night in old quarries to reduce the chance of detection by aerial reconnaissance.
At 0530 on April 9th (Easter Monday), the four Divisions of the Canadian Corps launched their attack from the tunnels as part of the Battle of Arras. In addition to taking the ridge, the battle was intended to pin German troops down while the French made a major attack further south. The Canadian attack followed unusually detailed briefing of all soldiers; the layout of the area was recreated well behind the lines to support briefing and rehearsals. In the preceding week there had been an intense bombardment against the German batteries and other defences. Many of the targets had been located by the Royal Flying Corps who continued to fly reconnaissance missions despite the appalling weather. The attack was successful and the Vimy Ridge was taken and held.
The site - still a sea of shell-holes - is now a Candian War Memorial Park dedicated to over 60,000 Canadians whio died in the war. There is a small but evocative museum decribing the campaign. Front line trenches only scores of yards apart have been preserved but it is difficult to visualise the true horror of the Western Front. As well as the surface features, one tunnel - the Grange Subway - has been preserved and can be visited as part of a guided tour.
The Grange Subway was built by the Royal Engineers between 1916 and 1917 and runs for about half a mile. As well as the main tunnel, there are a number of side tunnels which provided storage, hospital and command positions. Further small tunnels (saps) were used to lay huge mines under enemy lines creating immense craters which continue to scar the landscape.
The Memorial Park also includes an imposing limestone monumemnt inscribed with the names of over 11,000 Canadian Soldiers who gave their lives during the conflict and have no known grave.