Half a million lives lost for just eight kilometres gained – the stark numbers behind the Battle of Passchendaele.
But although it came to typify the waste and futility of World War One, Allied commanders had high hopes for the battle when it began on July 31st , 1917.
Designed initially to drive German forces back from the Ypres salient, it was hoped forces could push on and recapture the Belgian ports from which the Germans were launching damaging U-boat attacks.
But what army planners hadn’t counted on was the unseasonably heavy rain that turned the battlefield into a quagmire, making progress all but impossible after the first few weeks.
In the end - following more than three months of bitter fighting - the offensive ground to a halt on November 6th, the day Canadian troops took the tiny village of Passchendaele.
The 38th (Welsh) Division was heavily involved in the first weeks of the fighting.
On the opening morning, it was tasked with taking Pilckem Ridge, a heavily defended German position dotted with pillboxes and bunkers.
By the end of the day, the division had captured all its objectives. It also captured 700 prisoners, inflicting such heavy losses on the German third Guards Division that it had to be withdrawn from the front line.
Two Welsh soldiers – James Llewellyn Davies (who died of his wounds) and Ivor Rees won the Victoria Cross for their actions in the battle; a third Welshman, Robert Bye, also earned the VC on July 31st for actions elsewhere on the front line.
On Monday, descendants of those who fought - plus senior army figures, dignitaries and politicians - will assemble at the Welsh Memorial Park in Langemark, near Ypres, to remember the battle and the sacrifices made by those who fought.