They fought, they faced extraordinary obstacles and they marched.

But with the number of diggers dwindling each year how do you preserve the Anzac spirit for future generations let alone answer all those questions that children ask?

For Adelaide mum Belinda Duffield, the daughter of a proud Aussie submariner, the answer was simple – write a book.

It's called "Hey Pop … What's that medal for?" It tells the story of Roger Saltmarsh, a lead marine engineer during the Vietnam War and other missions through the inquisitive eyes of young children.

Apart from Roger's own brave and exciting experiences at sea. The book serves as an easy to follow guide about what it means to be an Anzac and serve your country with interactive tasks for parents and children.

From a handful of copies to now becoming available at many Adelaide post offices, Deli's and primary schools.

Understandably Pop is pretty proud too as he readies his medals for another march with his mates tomorrow.