The 15th Battalion was originally raised as part of the all-volunteer Australian Imperial Force (AIF) in September 1914. Drawing personnel from volunteers from Queensland and Tasmania, it formed part of the 4th Brigade, along with the 13th, 14th, and 16th Battalions. With an authorised strength of 1,023 men, the battalion initially consisted of eight companies, of which six came from Queensland and two from Tasmania. The Queensland companies concentrated at Enoggera in September and began initial training, while the Tasmanians formed at Claremont in October. In late November, the battalion concentrated at Broadmeadows, Victoria, under the command of Lieutenant Colonel James Cannan, who later rose to become Quartermaster General during World War II. Many of the battalion's officers and non-commissioned officers had previously served in the Citizens Forces and a few had fought in South Africa during the Boer War or in India with the British Army. Following a short period of training, the battalion embarked for overseas on the transport ship SS "Ceramic" in late December 1914, after marching through the streets of Melbourne. Initially it had been planned to send the Australians to fight against the Germans on the Western Front, but overcrowding and poor conditions in the training camps in the United Kingdom had resulted in the first Australian contingent, the 1st Division, being sent to Egypt instead. There they commenced training and briefly undertook defensive duties around Kantara, when Ottoman forces raided the Suez Canal.