On April 9, 1917, the four Canadian army divisions fought as a unified force for the first time, accomplishing what was thought impossible by the British and French forces - they captured the heavily fortified Vimy Ridge, 175 km north of Paris, France. An estimated 20,000 Canadians were in attendance.
The War Museum also opened its doors to the public Sunday for a free visit and a live stream viewing of the sister ceremony at the Canadian National Vimy Monument in France.
The battle across a 7km (4.3-mile) ridge began in heavy snow and sleet and lasted four days.
Canadian Prime Minister Justin Trudeau is among the dignitaries commemorating the centenary of the World War I battle of Vimy, in northern France. The commemorative ceremony at the memorial honors Canadian soldiers who were killed or wounded during the Battle of Vimy Ridge in April 1917.
There was also a clear effort to include Canada's indigenous people, who played a significant role in the First World War.
William and Harry - who have both served in the armed forces - will lay a pair of boots, some of the first of thousands that will be placed at the site by Canadian and French youth - representing nearly 3,600 Canadians who died during the battle. "Vimy, many scholars have said, was the formation of a nation".
Virtually every Canadian prime minister has appealed to the unifying power of Vimy Ridge over the past century, and Justin Trudeau did the same Sunday on the 100th anniversary of the historic First World War battle. "And they remind us that one can not exist without the other".
But he saved a special thanks for Canada, telling Trudeau and the hundreds of others assembled that the Canadians' actions at Vimy were "a turning point for our city and our country". Yes, Vimy's soldiers are telling us nationalism only leads to war and fundamentalism to destruction. In the words of one veteran: 'We went up Vimy Ridge as Albertans and Nova Scotians.
"Their sacrifice must inspire us to do everything to avoid that senseless losses happen again", Charles said of the long-ago Canadians who lost their lives in France.
"For others, Vimy represents Canada's transformation from a British colony to a country confident of its place in the world and worthy of other's respect â€" what some call its coming of age as a nation.