From Charles de Gaulle to the teenage son of Rudyard Kipling, and forgotten names from across the globe, the story of the millions captured or missing in the First World War is now laid bare with a mouse-click, after the Swiss government funded the $4.3-million digitization project.
"It took us three years to restore the index cards, and another three to digitize them," said David-Pierre Marquet, archivist at the International Committee of the Red Cross.
The haul of files is searchable at icrc.org/ww1
The originals, inscribed into UNESCO's Memory of the World Register in 2007, are stacked in tall glass cases filling an entire hall at the ICRC museum in Geneva.
The ICRC created a special tracing division just two weeks after the war broke out in 1914.
Hundreds of ICRC volunteers spent the war matching family enquiries passed on by local Red Cross branches with lists of POWs obtained from the belligerents.
"The ICRC would be able to reply that 'Your father's alive, he's in this particular camp,' and they could send a Red Cross message to re-establish family ties," Marquet told AFP.
The ICRC continues to play that role in the age of Skype.
ICRC staff also visited POW camps worldwide, and their reports have likewise been digitized.
"The ICRC was an intermediary, guaranteeing correspondence between prisoners and their families, and verifying conditions of internment and captivity," ICRC historian Fabrizio Bensi told AFP.
Most of the card-file volunteers were women, since Swiss men aged 20 to 50 were called up to protect the borders.
They produced alphabetical index cards with basics such as name, regiment, date and place of capture and site of detention.
Sub-files detailing tracing efforts and ICRC responses swelled the total number of cards to six million.
It was a mammoth task in the pre-computer era. "It was the first time that so much international information had been centralized," said Marquet.
A century on, history buffs are thrilled.
"What a wonderful gift to the descendants of the men of all countries who fought in World War I," said Briton Jenni Dobson, who found details of her 24-year-old grandfather William Allen, captured in France in September 1916.
"I got a real buzz," she told AFP.
The file confirmed the family story that Allen's parents received a letter from him saying he had been wounded and captured.
"The ICRC records show he was in a hospital. He recovered enough to survive his imprisonment and return home to marry and raise a family," said Dobson, who was ten when her grandfather died in 1957.
Fellow Briton Stephen Laccohee found information about his grandfather James Donovan, captured in Belgium in April 1918 at the age of 19.
"The family used the Red Cross tracing service," Laccohee told AFP.
Donovan, who died in 1962 when Laccohee was seven, never discussed his time as a POW but was clearly marked by his tough times.
"At the dinner table he would say 'You must eat your dinner, do not leave any'," said Laccohee.
Deep wartime scars
The files include individuals who later won fame.
One is future Second World War French leader and later president Charles de Gaulle.
The 25-year-old captain was wounded and captured in 1916. He spent the rest of the war in a string of camps, despite multiple efforts to escape.
"He writes regularly," says a penned note on his card.
Overwhelmingly covering the Western Front, the files underscore the global impact of a war that drew in 44 countries plus their colonies.
Besides Britons, French and Germans, the POWs number Australians, Canadians and Indians, and counterparts from French-ruled West and North Africa.
Hints of heart-rending stories are offered by POW death dates added to the cards, or the "negative sent" note which indicated that the person was not traced.
The entry for 18-year-old Second Lieutenant John Kipling, missing in action in September 1915, details repeated requests by his author father.
British writer and patriotic icon Rudyard Kipling had pulled strings to get his short-sighted only son John into uniform.
He is said to have been consumed by guilt for the rest of his life.
The 2007 film My Boy Jack, starring Daniel Radcliffe as John, told their story.
Such files offer snapshots of deep wartime scars, said London School of Economics historian Heather Jones.
"Unprecedented numbers of men who were reported missing were in fact dead and their bodies never found due to the nature of the heavy shelling of the battlefields," POW expert Jones told AFP.
"It took years before the public in Europe realized this: only in the decade after the war did many families finally accept that the 'missing' with no known grave were truly lost forever."