Wackett was born in Townsville, Queensland, on 2 January 1896. He joined the Australian Army and graduated from the Royal Military College, Duntroon, then with the rank of lieutenant joined No. 1 Squadron of the Australian Flying Corps (AFC) which had formed at Point Cook the day before his 20th birthday. He was one of twelve pilots that went to Egypt with the Squadron to operate in support of the Sinai and Palestine Campaign, embarking on 16 March 1916 and arriving at Suez four weeks later.