Britain's Charles, Prince of Wales, left, Britain's Prince William, Duke of Cambridge and Britain's Prince Harry, right, attend a ceremony marking the 100th anniversary of the Battle of Vimy Ridge at the WWI Canadian National Vimy Memorial in Vimy, France, Sunday, April 9, 2017.
While Canada's prime minister Justin Trudeau said: "The burden, they bore".
Hollande, Trudeau and British princes Charles, William and Harry were to take part in a ceremony later on Sunday expected to draw some 25,000 people.
"All the units in Calgary have a connection back to that First World War battle, and I couldn't be prouder of what's been accomplished today, bringing the community together, the citizens of Calgary to commemorate this historic battle".
Canada lost over 3,500 soldiers in the push, but ultimately captured the position from German forces, helping to forge a reputation Canadian troops maintain today.
Others are former or current military members for whom the event holds great significance.
There had been bloodier battles for the Canadians - 24,000 were killed or wounded at the Somme as compared to 11,000 at Vimy. It is truly an honour to be here to recognize the more than 650,000 courageous Canadians who served in the First World War and commemorate our proud history.
It's the moment, they say, when Canada was born - or at least came of age as a country.
The attack on 9 April sparked four days of intense fighting, until Canadian and British forces retook the heights overlooking the Douai Plain, which was still occupied by the enemy.
The cemetery is the final resting place for thousands of soldiers from the Great War, including 700 Canadians. "I went to Vimy Ridge and checked it out and I found his gravestone and took pictures". Let us remember those soldiers who sacrificed so much and let us strive always for a better understanding of our history and for peace. "Let's renew our commitment to remember their heroism in the face of suffering and fear".
The government of Canada hosted Sunday's somber ceremony of official speeches and performances by Canadian artists such as singer Loreena McKennitt.
The centre of the poppy is formed by a newly-unveiled sculpture of pairs of soldiers' feet by New Zealand artist Helen Pollock.