He was only 9 and the "old man" who came home never spoke about what he had been through.
His father would often go to bed early and would kneel beside it first - so one evening he asked him whay he did that.
"He said 'I could never tell you'," Mr Wilson told the silent and thoughtful young faces before him.
"He never talked about the war and every Anzac Day I now sit and think about what they gave to me - gave to us all."
Vietnam veteran Peter Grant, who is Taradale RSA president and who once managed the Hawke's Bay Regional Prison, worked with his son Dale Grant to organise the special gathering.
Dale Grant is Department of Corrections area adviser and both saw it as a valuable way to inspire the young men undertaking the programme and to get them to think about the deep meanings of Anzac Day and also to seek out members of their own whanaus who may have been to war.
When he addressed the gathering, Peter Grant, who did 25 years' military service, asked the young men to consider doing three things.
"I would love for you all to put a poppy on (which they all later did) and give thought to what it is about."
He also asked them to "take a moment one day" and stop at a cenotaph and read the names.
"A lot of our people from here went off to war and I want you to think about that - look at those names."
And he asked they one day attend a dawn service.
"Do these things and we will be very proud of you."
Retired Warrant Officer Potene Lima, who has more than 20 years service including Vietnam, told of the shocking sights he saw of casualties, and there were gasps when he told of one man who had only two unbroken bones in his whole body after being hit by heavy shell concussion.
It clearly had an effect, and one 18-year-old said it was a day he would long remember.
"I think it will help me - definitely," he said. "I'm old enough now to listen to them and understand what they are saying.
"When Anzac Day comes now I know it's more than just a holiday - I will wear the poppy."
Mr Grant said the challenge was to break the cycle of offending for the nine young men.
"If we can do that it would be so valuable," he said.
"This has not been about us it has been about them - it is encouragement to them."