Vimy Ridge 1917: Sound Ranging, Subways and the Canadian Corps' Assault

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Vimy Ridge, a seven kilometer escarpment rising about 60 meters over the Douai Plain, had been held by the Germans since October 1914 and fortified with deep dugouts, while French attacks in 1915 had cost some 150,000 casualties. For spring 1917, the Canadian Corps under Lieutenant General Julian Byng brought all four Canadian divisions together for the first time, about 170,000 men. They trained small units in fire and movement, handed 40,000 maps down to platoon level, and rehearsed on plasticine models and taped courses. British tunnelers dug 12 subways, some over a kilometer long and ten meters deep, with light rail, water and hospitals.

The artillery stockpiled more than a million shells, one heavy gun for every 20 meters of front. The new No. 106 fuse burst on contact, cutting wire without cratering the ground, while flash spotting and sound ranging, developed by scientists including William Lawrence Bragg, located hidden German batteries. At 5:30 a.m. on Easter Monday, 9 April, in sleet blowing into German faces, mines went off and the infantry followed a creeping barrage, leapfrogging fresh battalions through four objective lines. Three divisions kept to schedule, but the 4th Division stalled at Hill 145, and the Pimple did not fall until 12 April.

• Counter-battery fire neutralized an estimated 83 percent of German artillery positions.
• The creeping barrage typically advanced about 100 yards every three minutes, with infantry close behind.
• At Hill 145 a battalion commander had asked that a German trench be spared for later use, and its machine guns cut down the advance.
• The Canadians lost over 10,600 casualties, about 3,600 dead, and General von Falkenhausen was dismissed for holding reserves 24 kilometers back.
• France granted Canada 250 acres in 1922, where Walter Allward's memorial stands on Hill 145 amid fenced-off ground still full of unexploded shells.