During WW1,Colin served initially with the Auckland Regiment, with the rank of 2nd Lieutenant. In 1916 he was awarded a Military Cross "For conspicuous gallantry in action. He organised and led a successful raid on the enemy’s trenches, displaying great courage and determination throughout.: (London Gazette Supplement 9.12.1916.). In November 1917 he transferred to the New Zealand Machine Gun Corps and was promoted to the rank of Lieutenant. Colin Hally was killed in action on 6th April 1918.