Born in 1894 in York, Western Australia, Harry Dickerson listed his occupation as a woodcutter when he joined the AIF on 7 September 1915. He was 11 years younger than his brother, James Dickerson who joined the AIF in October 1914. Harry enlisted in the 12th reinforcements to the 10th Light Horse and arrived in Egypt in February 1916, only a couple of months after the Australian forces were evacuated from Gallipoli. Serving with a depot squadron throughout most of 1916, Harry became ill in November and was hospitalised, then placed in an isolation camp at Moascar until February the following year. Soon afterwards he was sent on the Hotchkiss machine-gun course, passed as a first class machine-gunner, and was assigned to the 3rd Light Horse Machine Gun Squadron. He served with his unit throughout the Palestine campaign.
As the war drew towards its end in late 1918 Harry was detached from his unit to work in the provision of supplies at Damascus. He suffered some brief periods of illness, requiring hospital treatment, and eventually returned to Australia where he was discharged from the AIF in September 1919.