Nearly seven years after leaving the New Zealand Defence Force (NZDF), Victoria Cross recipient Willie Apiata is going back into battle.

This time, the former SAS soldier is fighting for the welfare and futures of the men and women who leave the services who, in his words, currently get nothing.

It says something about the pulling power of Willie Apiata VC that the launch of Post Transition at the Auckland War Memorial attracted so much interest on Thursday.

Post Transition is an organisation Apiata and partner Jen Martin have created to fill the void so many of our servicemen and women feel when they leave the NZDF.

In a launch video, Apiata talked openly about his service, and most tellingly, what happened next.

"I've lived it, I've experienced it and something needs to change," he said.

"I left, I had the highest award you could ever imagine that can be awarded to any serving person, and the day I walked out the gate I got nothing.

"I was on my own. No support from anybody."

He says if that happened to him then, how does a private soldier feel who's only done six years and wants to leave?

Among the things he's going into battle for now is better welfare and care for former NZDF personnel, particularly around the treatment of post-traumatic stress disorder (PTSD).

"You can't unsee what you see," he told Newshub. "The tragedy, things torn in front of you, the horrors. Even for the incident that I was a part of, I will never forget that. It will live with me until I die."

There's a saying that what happens in country stays in country, but Apiata says that's "the biggest myth I've ever heard".

"Nothing ever stays there, it always comes home, and it comes home in here."

He says his family gave him the stability he needed to get through, and now with his partner they're hoping to help others.

"We've made a very conscious decision with this process that actually, the way that we can get some healing and share the story of bravery is to go out and use the platform to help other people feel like they are not on their own," Ms Martin says.

So how big a problem is PTSD and mental health for servicemen and women in New Zealand? Apiata and Ms Martin anecdotally say it's huge, but it's hard to be accurate because there is no measure.

A recent report in the UK found 50 serving or former military personnel took their own lives in 2012, more than the number killed in action in Afghanistan.

"It was the scariest thing I've ever been a part of in my life," Apiata says.

"The thing I was most scared of was my mate, and that's what this is about. We never leave anyone behind, we've got to go back and help them more, in one way or another."

Breaking in wild horses is therapy for Apiata, as he says you need to be calm to gain their trust.

Crucially, he's hoping to gain the trust of employers; to get them to look beyond the stereotypes and give former servicemen and women a chance.

"[It] takes our men and women from the battlefield and into business and being purposeful people in the civilian population again."

Once named New Zealand's most trusted and honoured for valour, he's never been comfortable in the limelight. This might be his most courageous role yet.

"You talk about brave... I have to be brave to hop back in front of that camera and talk to you, which I don't do, because I don't like it. But I'm putting myself out here and my family, because this is so important.

"There are so many of our brothers and sisters that need all of us - not just me and Jen, but us all."

Newshub.