A New Zealand soldier is searching for the descendants of a German officer who saved his great-grandfather's life almost a century ago.

Private John Raymond Cullen was the sole survivor of a six-man machine gun post hit by German artillery fire in the battle to liberate the French town of Le Quesnoy in 1918 during World War 1. He attempted to return to friendly lines but was injured and bleeding and began to lose consciousness.

That's when he was discovered by a group of surrendering German soldiers led by officer H. Held from Hanover. Held ordered his men to remove their tunics and fashion a makeshift stretcher. They carried him back to his comrades, where he was given urgent medical attention.

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Private Hayden Cullen says his family are pinning their hopes on him to find the family of H. Held

Before being taken into captivity, Held gave Cullen his wallet with his name and family photo inside, which Cullen took back to the family farm. But his family were never able to find the German family to return the wallet.

"A century later, our family are still no closer to locating this officer to return the wallet to his family," his descendant Hayden Cullen, also a private in the New Zealand Defense Force, said in a social media video made in a bid to find the owner.

Cullen is traveling to Belgium in October as part of New Zealand's contingent to commemorate the 100-year anniversary of the devastating Battle of Passchendaele in the Belgian province of West Flanders.

Cullen hopes to use the trip to help his family find the ancestors of his great-grandfather's savior.

"We owe them a great deal for what their ancestor did for ours," Cullen said. "I know it's a long shot but if one miracle can happen — why can't another?"

More than 16,000 New Zealand soldiers lost their life in WWI and more than 41,000 were wounded. The recapture of the fortress town of Le Quesnoy was one of their last actions in the war, with soldiers using ladders to scale the city walls and fight the occupying Germans hand-to-hand.