Canada commemorates the centenary of the Vimy WWI battle

A sentry stands next to a torch of remembrance at the National War Memorial during a vigil to commemorate the 100th anniversary of the Battle of Vimy Ridge in Ottawa, Ontario, on Saturday, April 8, 2017. (Justin Tang/The Canadian Press via AP) (The Associated Press)

Two Canadian Mounted Police sit on their horses prior to a sunset ceremony and mounting of the vigil at the WWI Canadian National Vimy Memorial in Givenchy-en-Gohelle, France on Saturday, April 8, 2017. Commemoration ceremonies will take place on Sunday at the memorial to honor Canadian soldiers who were killed or wounded during the Battle of Vimy Ridge in April 1917. (AP Photo/Virginia Mayo) (The Associated Press)

A woman turns on electronic candles during a vigil to commemorate the 100th anniversary of the Battle of Vimy Ridge in Ottawa, Ontario, on Saturday, April 8, 2017. (Justin Tang/The Canadian Press via AP) (The Associated Press)

Canadian Prime Minister Justin Trudeau is among the dignitaries commemorating the centenary of the World War I battle of Vimy, in northern France.

About 20,000 people, including many Canadians, are expected to attend the ceremony Sunday, including French President Francois Hollande and British royals Princes Charles, William and Harry.

On April 9, 1917, the Canadians succeeded in taking the German's strategic post on Vimy Ridge — where past British and French attempts had failed. The move cost 3,600 dead and over 7,000 injured in three days.

The battle has become an important part of Canada's national identity, symbolizing the shift from a former British colony to a nation on its own.

The Vimy memorial also pays tribute to the 11,285 Canadian soldiers who died in France and have no known graves.