The Australian soldiers came under "the barrage of our own guns" after ending up too far behind the German trenches at Fromelles.
It was 7.30pm on July 19, 1916; the last time Private Albert Beck saw Private Leslie Clark Dunn.
Their 31st Battalion only entered the front-line trenches three days before the battle of Fromelles, the worst 24 hours in Australia's military history.
Private Beck said they made it hundreds of metres behind the last line of German trenches as Australian troops fought their first major battle on the Western Front.
"We got on too far and came into the barrage of our own guns," he recalled in January 1917, after Private Dunn was named on a German death list.
"We had to fall back and Dunn was not seen to come back with us."
He had already sent that information to Private Dunn's wife Lillian in Melbourne.
The mother of two young children - David, five, and three-year-old Edward - waited months for news after her husband was reported missing in France.
His death in the battle of Fromelles was confirmed in March 1917, a month after the Germans sent received the 28-year-old's identification disc to the War Office.
He remained on another list of the "missing" for more than a century: the 1299 Australian soldiers killed at Fromelles with no known graves.
"It's been a part of our family's almost folklore that, yes, our grandfather was killed over there," grandson Roley Dunn said.
"He was only young, he left young children behind and a young widow and 'we don't know where he is'.
"We basically had no real closure. He was just this mystical figure that we knew very little about."
Hopes of finding the soldier's final resting place were renewed by the discovery of an unmarked mass grave near Fromelles in 2007.
The remains of 250 men were recovered in 2009 and reburied the following year as 'unknown soldiers' in a new military cemetery.
Roley followed his older brother Leslie's lead in providing a DNA sample early on, but largely gave up hope their grandfather could be identified as years passed with no news.
In March, the family learned Private Dunn was one of seven Australian soldiers formally identified by the 2019 Fromelles Identification Board.
"The fact that they've now made an ID and that he will have a named grave gives a wonderful sense of closure to the whole thing," said Roley, who also has a sister Ellen.
Sadly, 77-year-old Leslie Dunn died in December.
"It is bittersweet that, yes, we have got closure on it but it's too late for him to hear about it," Roley said.
Leslie followed his father David and namesake grandfather into the military, serving as a Royal Australian Air Force pilot for 33 years.
His younger son Chris Dunn, who spent 15 years as a RAAF pilot, remembers being at Fromelles with his dad for the 2010 dedication ceremony at the new cemetery.
"It was actually quite emotional when we were there," Chris said.
"To walk through afterwards and see all of the unknown soldiers' headstones, it was quite eye opening."
The 5th Australian Division suffered 5533 casualties, including 1917 dead and 470 taken prisoner, at Fromelles.
The attack by Australian and British troops was meant to be a feint to stop German reserves moving south, but was a disaster.
Chris is proud of his family's four generations of military service, but laments the "utter waste of life" at Fromelles for little or no strategic gain.
"It really was just a complete tragedy."
Reading Private Dunn's war records, Chris was particularly struck by his great-grandmother's heart-breaking requests for information about her missing husband and later his death certificate and will.
"She's saying: 'I've got two young sons. It's hard to settle affairs if I don't know that he's actually been killed.'
"It's quite sad."
So far, 166 Australian soldiers have been identified among the 250 found in the mass grave after a search prompted by research by retired Melbourne teacher Lambis Englezos.
A number of members of the Dunn family plan to go to Fromelles in July for the annual commemoration ceremony at the Commonwealth War Graves Commission Fromelles (Pheasant Wood) Cemetery.
Roley is amazed that he will stand on the soil where the battle took place and see his grandfather's grave.
"As a 28-year-old in 1916 on that ground, he couldn't imagine that future generations in peace would be standing on the same soil, 103 years later."
Chris expects the ceremeony will be both emotional and comforting, knowing there is now a focal point for grieving.
"I think it's important that we continue to recognise those who paid the ultimate sacrifice over there, a long way from home."
Australian Associated Press