Why Did Canada Attack Vimy Ridge?

Previously, France had attempted to take Vimy Ridge, and were crushed, losing over 100,000 men. The Entente wanted to capture Vimy Ridge badly, this is because the ridge was essentially a stronghold that protected the many German forces stationed in the Douai Plain below the ridge. If the ridge was captured, then Entente forces had a perfect place to launch an attack on these soldiers. Capturing Vimy also stopped the Germans from being able to launch such an attack on the British forces stationed on the other side.

A map displaying Vimy Ridge at the time of the battle, and the positions of the Canadian Corps.
Source
"Vimy Ridge Maps." War Museum. Canadian War Museum, n.d. Web. 12 Oct. 2011. <http://www.warmuseum.ca/cwm/exhibitions/vimy/vimy_maps_e.shtml>.

The attack on Vimy Ridge was part of a British plan, which involved British soldiers on both sides of the ridge to storm through, while Canada took the ridge itself. If not for Canada succeeding, the plan would have failed, and much more people would have died.