Explanation From Wiki:

https://en.wikipedia.org/wiki/Battle_of_Vimy_Ridge

The Battle of Vimy Ridge (9–12 April 1917) was part of the Battle of Arras, in the Pas-de-Calais department of France, during the First World War.

Supported by a creeping barrage, the Canadian Corps captured most of the ridge during the first day. The village of Thélus fell on the second day, as did the crest of the ridge, once the Canadian Corps overran a salient against considerable German resistance. The final objective, a fortified knoll outside the village of Givenchy-en-Gohelle, fell to the Canadians on 12 April. The 6th Army retreated to the Oppy–Méricourt line.

Historians attribute the success of the Canadian Corps to technical and tactical innovation, meticulous planning, powerful artillery support and extensive training and the inability of the 6th Army properly to apply the new German defensive doctrine. The battle was the first occasion when the four divisions of the Canadian Expeditionary Force fought together and it was made a symbol of Canadian national achievement and sacrifice. A 100 ha (250-acre) portion of the battleground serves as a memorial park and site of the Canadian National Vimy Memorial.[5]