Frank was among the first Anzacs to storm the beaches of Gallipoli on April 25, 1915 and received the Military Medal for his courage under fire. He was later commended for a Distinguished Service Medal in 1918.

When the War ended Staff Sgt Cahir stayed behind and commenced working in 1919 helping to locate, exhume, identify and photograph the graves of soldiers who had died in battle. The approximately 1100 men who stayed like Frank did were in the main a rowdy lot. Accusations of misconduct included an officer taking a photograph of an Australian skull with an Australian hat and cigarette clenched between its teeth– ultimately leading to a Court of Inquiry in 1920.

Many of the witnesses, including Frank Cahir in evidence to the Court of Inquiry accepted that a great deal of improper behaviour was simply a way of coping with the ‘gruesome task, which was disliked by all, and frequently made the hardiest sick, but it just had to be done.’

Men like Frank spoke of their work as a dreadful but necessary task.

Franks’ co-workers plaintively voiced their feelings. “God, how sick I felt … I don’t know how many we buried. I’ll never forget that sight … the most dreadful experience even I have had … I retched and have been sleepless since … No words can describe the ghastliness.”

Frank worked principally as a photographer though he was not a professional photographer. Presumably he was chosen to be an Australian Graves Detachment (AGD) photographer on the basis of his knowledge of chemicals (he had trained to be a chemist before the War began) or perhaps he simply showed an aptitude for the use of a camera. Frank and the other photographic staff were tasked to systematically document Australian graves in cemeteries across the regions where many thousands of Australians had died in combat.

The concept for the capture of images of the graves was that it provided a record of the sacrifice of Australia war dead, and proof to bereaved Australian public, that their loved ones were being commemorated and recognised. He did not return home until 1921.

Frank married and had three sons but his return to Australia was marked by a rapid deterioration in his physical and mental health – characterised by bouts of deeply introspective behaviour.

He suicided in 1928, presumably suffering from PTSD, leaving behind a widow and three sons.