Alexander was born at Shannon Vale near Glen innes and was one of three sons of David and Rosa Gibbs to serve during World War 1. He enlisted at Liverpool in October 1914 when he was twenty three years old. His elder brother Arthur enlisted a day later and his younger brother, Leslie, enlisted in February the following year.
Alexander, a Private with the 4th Battalion, 2nd Reinforcements, sailed from Sydney for Egypt on HMAT A48 Seang Bee on 11 February 1915. His Battalion was quickly sent into battle at Gallipoli. Only three months after leaving Australia he was killed in action and buried at the 4th Battalion Parade Ground Cemetery at Gallipoli.
His few remaining possessions consisting of a cigarette case, testament, pipe and letters were returned to his Mother in 1916. As a result of Alexander's death his Mother was granted a pension of one pound per fortnight from August 1916.
Private Alexander Gibbs has his name inscribed on the Inverell Honor Roll and Cenotaph and in 1919 a memorial tree was planted for him in Kurrajong Parade.