"We didn't know about the New Zealanders and the Australians. We were the bravest of all," Mr Van Duyse recalled during a recent visit to Wanaka's war memorial.
It wasn't until he began finding artefacts in fields that he realised the extent Allied Forces were involved in defending his nation.
He began a life-long mission to promote the war history and maintenance of war cemeteries.
The former journalist and business adviser now works as a historical adviser for a Flanders events and travel organisation and is on a lecture tour of New Zealand to promote awareness of the city's efforts to keep wartime memories alive.
"I am amazed there are so many New Zealanders knowing about the First World War - much more than in Belgium. Most of them have relatives who were there," Mr Van Duyse said.
During World War 1, one in 10 New Zealanders enlisted - accounting for 120,000 men and women.
More than 18,000 were killed overseas, with one in four New Zealand men between the ages of 20 and 45 either killed or wounded, Mr Van Duyse said.
More than 4600 New Zealand servicemen are buried in Flanders Fields and the largest of 80 cemeteries, Tyne Cot, contains graves of more than 520 New Zealanders, more than any other cemetery outside New Zealand, he said.
The city of Messines is regarded as "the most New Zealander city in the north of this globe", where New Zealanders were involved in a major battle on July 31, 1917.
Three weeks late, the battle of Passchendaele began, with the New Zealanders involved from October 4, 1917.
New Zealand casualties were high that day, with 20% of those taking part killed or injured.
By October 12, the NZ casualty toll had risen to 60%, with 1200 dead and 1500 wounded.
Mr Van Duyse said he supported the suggestion of Henry Barker of Frankton, who recently called through the ODT letters to the editor for the name of his great-uncle Thomas Galvin, of Cardrona, to be added to the Wanaka monument.
Mr Galvin is listed as missing in action after the 1916 Battle of Somme and his name is not on a local war memorial but is on a memorial in Caterpillar Valley, France.
Mr Van Duyse said Flanders had a monument for people missing in action and as recently as last year missing Australian soldiers' bodies had been discovered in fields and identified by DNA testing.
