Of the many beautiful cemeteries looked after around the world by the Commonwealth War Graves Commission, the largest lies on the side of in Belgium.
The bodies of nearly 12,000 men lie in Tyne Cot Cemetery, most of them unidentified. Another 35,000 whose bodies were never found are commemorated on a memorial wall at the top of the plot. Look back down the slope: you can see the town of Ypres below, only about five miles away.
The men whose ghosts surround you now died fighting for this ground, battling up towards the village of Passchendaele which gives the battle its nickname.
Properly known as the Third Battle of Ypres, it is a byword for the futility and horror of war. Of the British, Commonwealth, French and German troops who fought here, nearly half a million were killed, wounded, captured or simply disappeared.
You could walk in a couple of hours what it took the British three and a half months to win. They had accomplished few of their original objectives.
True, they had shown their Belgian, French and Russian allies that they were prepared to play their part in the war. More immediately, they had made more secure both Ypres and their supply ports at Calais and Boulogne. But ambitions to cut enemy rail lines and force German U-boat submarines from their bases on the Belgian coast remained a dream.
The German army had been worn down, but only at a terrible cost in experienced British troops too.
The initial British assault on 31 July was too ambitious and results fell far short of expectations. Attempts throughout August to push on regardless were disjointed and achieved little more.
Drier weather in September, a new commander and new tactics allowed them to begin to grind through the German defences, but casualties remained heavy relative to ground gained and in October and November downpours of rain made the battlefield a morass of mud.
Progress slowed to a crawl. By the time the offensive was suspended on 10 November, the two sides had fought each other to a stalemate amid appalling conditions for the soldiers.
Shivering under cold rain in what little shelter they could find amid a wasteland of muddy shell craters poisoned with lethal gas, for them it was, as one German general put it, ‘no longer life at all. It was just unspeakable suffering.’
This was a battle which was allowed to go on too long. Passchendaele, like Stalingrad or Sangin in later wars, took on a symbolic significance far greater than its strategic value.
Too many brave soldiers on both sides died for that symbol. Lessons were learnt which contributed to allied victory in 1918. But the most important legacy of this terrible battle is, perhaps, the courage of those men.
Jonathan Boff is Senior Lecturer, Department of History, University of Birmingham