Marshal Ferdinand Foch of France, Commander-in-Chief of the Allied forces, chose the Canadian Corps to spearhead a massive assault on the German defences near Amiens. He deployed the Canadians along the Ypres sector in order to mislead the Germans into believing that the Allied offensive would be initiated there. Then he secretly redeployed the Canadian Corps further south.
Lieutenant-General Arthur Currie, who had succeeded Lieutenant-General Julius Byng as commander of the Canadian Corps on 9 June 1917, decided to launch the assault without a preliminary artillery bombardment. When a battery is moved to a new position, it normally "registers" the guns, that is, it fires at least one gun per fire unit (troop or battery) to confirm the "paper" calculations. When the guns moved into their final positions for the assault, no such registration shoot was done. Rather, the gunners made abnormally detailed survey and other calculations. The precision of these measurements was really the crowning glory of the many technological innovations pioneered by the Canadian gunners. As a result, the Germans were totally surprised by the attack. Flanked by the Australians and a large formation of British tanks, the Canadian Corps drove deep into the German defences. By midday, they had advanced over seven miles and captured 15,000 prisoners and 400 artillery guns.
The Canadians had created such a breach in the German defensive alignment that the German chief- of-staff, General Erich von Ludendorff, called 8 August "the black day [der Schwarze Tag] of the German Army" and advised his government to seek an armistice with the Allies.
