April 9th, 1917 was Easter Monday, and also the day that the Canadian Corps under Canadian leadership launched its assault on German positions on Vimy Ridge. In a few days, they had succeeded in capturing the ridge. Canada's main memorial to her missing of WWI sits atop the ridge.
I have probably posted this photo before. It was taken in 1986, from our tour bus as we left the area, having spent some time in the tunnels under the ridge.