The royals were out in full force Saturday for the 100th anniversary of the Battle of Vimy Ridge in northern France. Prince Harry, Prince William, and Prince Charles were joined by Canadian Prime Minister Justin Trudeau and French President Francois Hollande to honor the soldiers who died in the WWI battle.

Credit: Samir Hussein/WireImage

During the ceremony—which was attended by an estimated 25,000—both William and Harry laid a pair of boots and poppies of remembrance of the fallen at the Canadian National Vimy Memorial site. The boots are the first of thousands set to be placed at the site by Canadian and French youth, representing almost 3,600 Canadian soldiers who died in the battle.

VIDEO: Prince William, Prince Harry Honor Fallen Soldiers with Justin Trudeau

The somber event comes just days after William and Harry attended another mournful ceremony: the multi-faith Service of Hope at London's Westminster Abbey that paid tribute to the victims of the London terror attack on March 2. There, the Duke of Cambridge laid a wreath of red and white blooms at the Innocent Victims memorial along with a hand-written note dedicated to the police officer killed in the attack that read: "For PC Keith Palmer, and all those who have served our community so valiantly. Your legacy is our way of life. William."