The sights and sounds of war, its tastes and smells, are hidden from those of us who, mercifully, know it only from the screen or the page.
Jack Davis, 106, is the oldest survivor of the First World War trenches, one of a dwindling few who cannot forget what it was like here in Ypres. He will give the exhortation during the Armistice Day service under the gate's arch, a memorial to 50,000 men who died without burial, many swallowed by the mud that surrounded the devastated town.
Jack should have been sent to defend the Lakenhalle, the Cloth Hall, but his orders were changed at the last minute. He has often wondered why, and will do so again this morning as he stands erect amid pomp and ceremony. The years will vanish from his mind; he will be 22 again. Scores of men from C Company of the Duke of Cornwall's Light Infantry will be settling into the basement of the Lakenhalle. The German heavy artillery will once more bring the building down on their heads.
"There was 10 minutes' grace before the next barrage. That was the only time available to try to rescue those buried under the rubble," said Jack. "It was hard to do anything for them. There were many casualties among the rescuers. When the Last Post is played on Sunday I will be thinking of my friends who died then, many of whom I had soldiered with since 1915."
The determination to remember has brought Jack back to Ypres, surely for the last time. He left his nursing home in High Wycombe on Thursday with his son Ken, 76. They stayed with the Chelsea Pensioners in London before the long drive to the borders of Belgium and northern France. Three fellow survivors of the First War, all older than 100, were also on board with a paramedic, a historian and 44 other pilgrims with the Genesta Battlefield Club. Most had relatives buried or lost in Flanders. One lady was born three months after her father died and has been visiting his grave since 1927.
The tour party is staying at the Rabbit Inn at the edge of the town now known as Ieper. Trench maps show it to be the site of Frascati, a ruined building nicknamed after a London nightclub. Officers dined in the ruins, even as shells fell on the trenches nearby.
The background noise at our own dinner on Friday night was too much for Jack, who sat isolated and silent. But afterwards, in a quiet room, this slight, pale man in a black three-piece suit and regimental tie became animated as he explained why it had been so important to come back in person. "This is a very emotional thing for me," he said. "The generations of villagers here must have heard the stories about what happened so many times, but imagination cannot stretch to what we saw. Only those who served then know the horrors. When I look at what is happening in the world today, I wonder, was it worth it? Still, we are a living reminder that this is not just a story, something made up. It happened and cannot be denied. They know that, when they see us standing there."
Jack was too tired to make it to the gate on Friday to hear the Last Post played, but several hundred other people of all ages braved the bitter cold. They saw Arthur Halestrap, 103, cast off his raincoat, hat and scarf and stand up as straight as he could, with a chestful of medals thrust out. He recited the familiar words of Laurence Binyon's poem "For the Fallen" in a feisty voice, as though reminding all present that it was our duty to remember and it would damn well do us good.
Soldiers and their middle-aged children stood straight and still, but many of the younger people lacked the physical vocabulary of their elders. Unsure how to react to the silence, they looked away, shuffled about, or tried to imitate those standing to attention. The unusual atmosphere challenged them, and some were moved by the sight of a frail old man seeming to grow before their eyes, as he became a soldier standing alongside his fallen comrades. After the piper, the marching band, and the national anthems, he was crowded by people who just wanted to shake his hand.
With only a handful of veterans left, these men have become living icons. Whether they personally were heroes or not, they have come to represent the heroism and folly of war – at a time when it no longer seems quite so distant.
Colin Butler, the Genesta tour organiser, said: "I defy anyone with an ounce of compassion not to fill up inside when they come here. I have promised these men that when they are gone we will keep coming back. They will be remembered."