The Invercargill man joined the Invercargill Cadet Unit in 1988 after working as a police constable for decades.
Since he joined the unit, he had seen hundreds of cadets go through.
"I know that some of them have got a lot out of it.
"You see a young person come along at 13 and they're that shy that they can't look at you in the face ... and four years later, they're standing up like ... They're taller than me and looking down on me.
"There's been some great young people go through the unit since I've been there."
The unit was a voluntary programme which had helped many people to find pathways in their lives.
While many did not continue their training in the air force, army or navy, the young people who went through the unit learnt essential life skills.
"One of the main focuses is leadership. We try to teach them how to be a team member, how to work in a team.
"And then, if necessary, to be able to step out of the team and lead it ... because that's hard for someone of that age, 14 or 15, because they haven't got that confidence to do that."
Maj Kelly acknowledged the unit might not be for everyone, but he felt proud of many of the cadets who had made the most of it.
He remembered one story which exemplified how his work could change someone's life.
Years ago, a man returned to show his two children the place where he was brought up and said the unit had saved his life.
"The man told me he came here in the early 2000s and that he was in a very abusive home. His father was a drunken alcoholic who knocked him and his mother around.
"He said, `I was on the verge of suicide on a number of occasions, but then I found [the] cadets'. He told me that he started coming here and it became his anchor point.
"It was the only place that he enjoyed going to, the only place he was treated as an equal. And he said, `it saved me'."
It was a privilege to wear the military uniform and represent New Zealand.
"It is an honour. It's a pride thing and we try to teach them to be proud of themselves, proud of their unit and proud of each other. It's, for me, a big thing."
He believed it was now time for him to say farewell to the position he had filled for almost half of his life.
However, he said he would still be involved in the organisation.
"I'm just going to miss the friendship, the comradeship. The officer team down there is a good team and they're doing a good job with the cadets.
"But all good things must come to an end and this time has come to me," he said.