Arthur was born in Castlemaine, VIC in 1897 to Arthur Beaumont O'Hara and Ada Charlotte Webber.

Arthur was a telegraphist and gave his address as Bacchus Marsh, VIC when he enlisted in the AIF on the 23^rd of October 1916, aged 19½ - his parents consent having been given. He spent a month at signal school (wireless) in October before being sent to the Australian Flying Corps camp at Laverton, VIC in February 1917. He embarked aboard the HMAT A9 Shropshire in May, disembarking at Plymouth, England in July.

A month after arriving in England Arthur was attending a school of wireless before he embarked from England in January 1918, arriving in Egypt almost three weeks later. He was detached to the Royal Field Artillery before being admitted to the 47^th Stationary Hospital, suffering from malaria MT. A week later he was transferred to the 14^th Australian General Hospital and then to a rest camp in in August. In September he was again with the Royal Field Artillery again for a month and re-mustered as a wireless operator in December before embarking from Egypt aboard the Port Sydney in March 1919, returning to Australia in April and was discharged from the AIF in May.

Arthur died at Bendigo, VIC in 1933, aged only 36 - most likely due to the malaria he suffered during the war.

He is listed on the Shire of Bacchus Marsh Roll of Honour, the Bacchus Marsh & District Roll of Honour and the Postmaster General's Department Victoria 1 Roll of Honour.