At least 846 Kiwi men died or were mortally wounded in a failed attempt to take the Passchendaele Ridge.
A remarkable story of kindness in the midst of war has emerged as a Kiwi soldier attempts to close a century-old battlefield mystery by the simple return of a wallet.
The empty wallet belonged to a German officer who saved the life of Private Ray Cullen, the great-grandfather of servingKiwi soldier, Private Hayden Cullen.
The paths of the two men from opposite ends of the earth crossed when Ray Cullen, a member of the New Zealand Machine Gun Corps, was involved in the legendary Kiwi liberation of the French township of Le Quesnoy in November 1918.
According to letters home, during a German artillery barrage a shell exploded in the machine gun post occupied by Ray Cullen and five others.
The young soldier was the only survivor and, seriously wounded, attempted to get back to friendly lines. He collapsed because of blood loss, but was saved when a German officer and his men, who were coming to surrender, stumbled across him.
The officer told his men to make a stretcher from their tunics and Ray Cullen was carried to medical attention.
Before being marched to captivity, the officer gave his wallet - with the name H. Held written inside - to the man whose life he had saved, and it ended up back at the Cullen family farm outside Te Awamutu.
Over the years, his family had attempted to identify the family of the wallet's owner, but to no avail, Hayden Cullen said.
The wallet German officer H. Held gave to Private Ray Cullen during the liberation of Le Quesnoy in 1918. Photo / Supplied
But there is new hope the mystery can be solved after Private Cullen, a member of the New Zealand Army Band, was chosen to join the New Zealand Defence Force contingent travelling to Belgium for the Battle of Passchendaele centenary on Thursday. His family were "pinning their hopes on me" to bring closure to the story of his great-grandfather and the German officer, the Cambridge soldier said.
"I know it's a long shot but if one miracle can happen, why can't another? You never know who you might meet over here - even 99 years later.
"Failing that, I'm hoping the power of the media and social media will connect our family with the family of the German officer - Herr H. Held, of Hannover.
"We owe them a great deal for what their ancestor did for ours."
The New Zealand National Commemorative Service for the Battle of Passchendaele centenary is at Tyne Cot Cemetery on Thursday morning (10pm NZT) .
A sunset ceremony will follow at Buttes New British Cemetery (6.15am Friday NZT).