By Jonny Dymond
BBC News, Verdun
There are few settings as dramatic, or depressing, as Verdun.
Schoolchildren took part in the ceremony alongside President Sarkozy
The centrepiece of the battlefield is the Great Ossuary, a building of grey and blackened stone 137m (150 yards) in length that houses the bones of 130,000 soldiers cleared from the battlefield in the decade after the war.
Rolling down the slope in front of the ossuary is a field of tombstones, mainly simple stone crosses. The graves of 15,000 soldiers lie here.
At the bottom of this field dignitaries gathered under a heavy grey sky: French President Nicholas Sarkozy; the heir to the British throne, Prince Charles; the Governor General of Australia, Quentin Bryce; the President of the upper house of the German Parliament, Peter Mueller.
A guard of honour stretched down the long line of graves, and Prince Charles and President Sarkozy walked along it. A solitary horn sounded, muffled in the cold air.
President Sarkozy laid a wreath at the foot of the flagpole that rises above the field of graves.
A constant cold wind drove the clouds overhead. Now and then the grey cover broke, allowing sight of blue sky and sunshine.
As the ossuary bell tolled, President Sarkozy accompanied two schoolchildren to one of the small stone crosses marking each grave. Flowers were left.
Then the group of politicians and military men made their way into the ossuary. Inside, 3,000 names of fallen soldiers are carved into the stone.
President Sarkozy and his wife Carla stepped forward. He lit the flame of remembrance, and stood as the yellow flames flickered in the great granite bowl.
Outside the ossuary, the president addressed a crowd of veterans of other wars, schoolchildren, and local people dressed in period costume.
He spoke of reconciliation between France and Germany, and of the huge number of different nationalities who came and fought for France.
"France will never forget the children who have fought for her," he said.
"France will never forget the blood spilt on the Marne and on the Somme and at Verdun."
Beyond the statictics
About a quarter of a million men died at Verdun. Eight and a half million were killed in the space of the four-year war. Four million were left widowed.
But President Sarkozy said we must look beyond the statistics
"Imagine the infinite pain of each victim," he said. "The pain of the child standing by his father's grave; that of the father and mother learning of the death of their son; the pain of the wife receiving a last letter from her husband.
"Behind each destroyed house, each devastated village, there was a deep wound that will never fully heal."
From this ceremony, for the first time in France, one thing was missing. No French veteran of World War I was alive to witness it. The last died in March this year.
As President Sarkozy and his guests drove away, and the crowd began to leave, the grey clouds, too, departed.
Sunshine poured down from a clear blue sky, and a brittle kind of peace descended upon Verdun.