In his final Anzac Day address, Governor-General Sir Peter Cosgrove has told veterans: "You matter. What you did matters."
Sir Peter spoke at the Australian War Memorial on Thursday for his final Anzac Day in the role, with his five-year commission coming to an end in June.
Thousands gathered in the autumn sun to pay tribute to servicemen and women, hours after the dawn service drew crowds of 35,000.
With flags at half-mast behind him, Sir Peter sought to explain to youngsters and service first-timers the significance of the day, and what brings people back year after year.
"In the gamut of motives from the profoundly philosophical to simple curiosity, there is a fundamental reason," he told the crowd in Canberra.
"It is by our presence to say to the shades of those countless men and women who did not come home or who made it back but who have now passed and to say to their modern representatives, the ones around the nation who today march behind their banners.
"You matter. What you did matters. You are in our hearts. Let it be always thus."
The former defence force chief offered a brief history of the First World War, seeking to highlight the vast numbers of men and women who left the shores to serve in uniform.
He paid tribute to the tens of thousands of people who never returned home, saying they were "gone but not forgotten".
It is for those souls that veterans march, he added.
"When we march we like to look at those gathered to watch and wonder, young and old, family, friends and strangers and to catch their gaze and convey our silent message," Sir Peter said.
"We did it for our nation, for what Australia stands for, we did it for you. Let it be always thus."
More than a dozen wreaths were laid following Sir Peter's address, including by government minister Simon Birmingham on behalf of Prime Minister Scott Morrison.
Sir Peter will be replaced by current NSW Governor David Hurley.
