Perhaps 50 Aboriginal soldiers fought on Gallipoli in an era when they weren't recognised as Australian citizens and enlistment was technically forbidden.
No-one really knows for sure, not even the Australian War Memorial which has sought to catalogue this little-appreciated part of Australia's military history.
Gary Oakley, war memorial indigenous liaison officer, says that's because indigenous enlistees didn't record their ethnicity on recruitment papers.
After the war, they returned to their communities, never marching on Anzac Day.
"Because no-one saw them, it skewed the perception of their service," he told the recent Anzac centenary conference in Canberra.
There are photos from the Western Front which clearly show Aboriginal soldiers. There are no known photos of Aboriginal soldiers on Gallipoli.
Still, the Memorial has identified some 50 Aboriginal men believed to have served on Gallipoli, with 13 killed.
It's thought 800-1000 indigenous soldiers served in Australian Imperial Force during WWI, with around 250-300 killed. That's out of an estimated indigenous population of 80,000.
There are occasional pleasant surprises. One related to Lance Corporal Richard Kirby who served at Gallipoli, France and Belgium.
"The only reason he got to be known to us was a family member came to us and said `I've got some medals I'd like to give to the war memorial and there's a DC something-or-other'," Oakley said.
That was actually the Distinguished Conduct Medal, second only to the Victoria Cross.
With the medals came a newspaper cutting showing Kirby with an Aboriginal woman. She, the relatives said, was his mum.
Kirby was awarded the DCM for a single-handed attack on an enemy machine gun post in France in August 1918. He took a bullet wound to the head, from which he died a week later.
Then there's Alfred Hearps, a third or fourth generation Tasmanian who served on Gallipoli. As a pre-war member of the cadet corps and militia, he was speedily promoted to sergeant and then to Second Lieutenant in France.
Hearps was grievously wounded by shrapnel at the battle of Mouquet Farm and has no known grave. Previously, it was thought Captain Reg Saunders was Australia's first indigenous commissioned officer.
Under the constitution, Aboriginal people weren't recognised as citizens. The 1903 Defence Act specifically exempted those not of substantial European descent from service in cadets and the militia.
But come 1914, recruiters weren't so fussed.
"I believe the Australian Defence Force, especially the AIF, was the first equal opportunity employer of indigenous Australians because they chose to ignore this rule," he said.
"If you fronted up the recruiter, all he saw was another soldier. He didn't care what colour you were."
However, medical officers at the recruiting depot had the final say. Oakley said some were racists, some stuck strictly to the rules, and others turned a blind eye.
Undeterred by rejection, many would-be soldiers just nipped down the road to another recruiting office. Some tried four or five times before succeeding.
In 1916, new recruiting guidelines stated that "Aboriginals, half-castes or men with Asiatic blood" were not to be enlisted. Again that was ignored.
From 1917, the enlistment rules said half-castes could be enlisted if recruiters were satisfied that one parent was European.
That raises the obvious question.
"Why the hell would you want to join a defence force in a country that doesn't class you as a citizen. The unfortunate thing is, we never asked anybody, we left it too late," Oakley said.
There are some ideas.
In the AIF, everyone was paid the same and that pay was good - six shillings (60 cents) a day for a private. That was comparable to a worker in Australia and far greater than pay to British soldiers.
Soldiers could send money home, though in some cases that was diverted by the various agencies which ran settlements and never reached needy families.
Then there was the warrior tradition - many joining up were only a generation away from traditional. Those who lived on mission settlements likely encountered the same propaganda which swelled recruiting throughout the war.
"Once in the service, as an indigenous soldier, you were treated as an equal; you have the same options for pay. When you are in the trenches, you don't have the option of disliking the person behind you," he said.
Sadly, that stopped the moment an indigenous soldier demobbed from the AIF.
Out of uniform and back in their communities, they resumed being just the same second-class citizens as before.