He was educated at St Peter's College, Adelaide and passed a three-year course at the School of Mines in electrical engineering.
After the outbreak of World War I Giles was transferred to the Australian Imperial Force and assigned command of the 10th Battalion's G Company.
[2] At the Battle of Pozières he was gassed and suffered multiple concussions from near misses of high explosive shells.
He persisted and led his men into defensive positions, conduct that brought him the second recommendation for the DSO.
[6] His conduct at the capture of Le Barque, where he harassed the German rearguard during their withdrawal, earned him a mention in Alexander Haig's dispatches on 9 April 2017, and later that year he was awarded the DSO for "services rendered in the prosecution of the war".