One chill Easter dawn in 1917, a blizzard blowing in their faces, the four divisions of the Canadian Corps in France went over the top of a muddy scarp knows as Vimy Ridge. Within hours, they held in their grasp what had eluded both British and French armies in over two years of fighting: they had seized the best-defended German bastion on the Western Front. How could an army of civilians from a nation with no military tradition secure the first enduring...