"I never would have known about the Rimutaka Crossing without the reenactment," Ms O'Connell said.
"It's a story that needs to be told -- and it's important for kids to know the history, so they can be informed and come to their own conclusion."
Ms O'Connell said she has always enjoyed writing, but began to write children's stories in 2000 after becoming an aunt.
When her eldest boy, Christopher, was four, she self-published a book called Rabbit Pox about the adventures of his soft toys, which she displayed at the Big Wai Art Sale.
There, she met Michael Smith, director of BMS books in Rotorua who eventually offered her a book contract.
The idea for her book, Leaving for the Front came as "one of those lightning bolt moments" after she and Christopher participated in the 2014 Masterton re-enactment -- dressed Lillian Wellington and her son John, who lived in their Perry St home in 1914.
She had the idea for The Crossing while writing the first book, having signed up for the Rimutaka march.
The book, told from younger son Michael's point of view, parallels her experience with Albert's journey over the hill, and off to the battlefield.
In the story, Michael is upset to see his mother leave for the march -- while, almost 100 years before, Albert's daughter, Ina, sadly watches her father leave for war.
"I can imagine it would have been so scary for Albert, not knowing if he was going to come home. By the time he left, things like Gallipoli and The Somme had already happened."
Albert didn't return until 1919, as he was critically ill with influenza.
"My grandfather was born after the war -- if Albert had died, our family would have ended in a grave."
Ms O'Connell said the march was an amazing experience, and captured the sensory detail in her writing.
"So much stuck with me -- the sound of the drums and the hobnail boots on the ground, the full moon, seeing the Southern Cross in the sky, and our shadows on the side of hill as we walked.
"A we neared the summit, it got quieter - there was anticipation in the air.
"When we got to the summit, watched the sun rise and heard The Last Post, there was a real sense of achievement - we've done it.
"It was such a moving tribute to my great-grandfather."