The Duke of Cambridge has led official commemorations marking the 100th anniversary of the Battle of Passchendaele.
William spoke on Sunday at the Menin Gate monument in Ypres, Belgium, as the daily Last Post was played ahead of Monday's centenary of the start of the bloody First World War British assault.
Flanked by the Duchess of Cambridge and Philippe and Mathilde, the King and Queen of the Belgians, he said Britain and Belgium "stand together" to remember those killed during weeks of heavy fighting in the summer and autumn of 1917.
Watched by some 200 descendants of those who fought, he said: "Today, the Menin Gate records almost 54,000 names of the men who did not return home; the missing with no known grave.
"Members of our families; our regiments; our nations; all sacrificed everything for the lives we live today."
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He added: "During the First World War Britain and Belgium stood shoulder to shoulder. One hundred years on, we still stand together, gathering as so many do every night, in remembrance of that sacrifice."
Sunday's poignant Last Post was the 30,752nd time it has been played since 1928.
The towering Menin Gate in the Belgian town is covered with the names of 54,391 British dead who have no known grave, according to the Commonwealth War Graves Commission.
In just over three months of conflict there were more than half a million casualties - 325,000 Allied soldiers and 260,000 to 400,000 Germans - in the Belgian battlefields.
It was fought between July 31 and November 10 1917 in battlefields that were summed up in poet Siegfried Sassoon's line "I died in hell, they called it Passchendaele".
