Between 9 and 12 August 1916 at Mouquet Farm, Pozières, during four days of very heavy fighting, Private O'Meara repeatedly went out and brought in wounded officers and men from "no man's land" under intense artillery and machine-gun fire.

He was promoted to Sergeant in late August 1918 and left England on 17 September 1918 on the troopship Arawa, arriving at Fremantle in Western Australia on 6 November 1918.

O'Meara had a mental breakdown in November 1918 at the Woodman's Point Quarantine Station south of Perth, shortly after arriving in Western Australia.

On 13 November 1918 he was transported to the 24th Australian Auxiliary Hospital, Stromness, where he was diagnosed on 19 December 1918 as: suffering from Delusional Insanity, with hallucinations of hearing and sight, is extremely homicidal and suicidal, and requires to be kept in restraint.

In July 2019 it was loaned by the Australian government to the National Museum of Ireland, where it will be on public display for twelve months.