The Australian Army was the largest service in the Australian military during World War I. The First Australian Imperial Force (AIF) was the Army's main expeditionary force and was formed from 15 August 1914 with an initial strength of 20,000 men, following Britain's declaration of war on Germany. Meanwhile, the separate, hastily raised 2,000-man Australian Naval and Military Expeditionary Force (AN&MEF), landed near Rabaul in German New Guinea on 11 September 1914 and obtained the surrender of the German garrison after ten days; it later provided occupation forces for the duration of the war. In addition, small military forces based on the pre-war Permanent Forces and part-time Citizen Forces were maintained in Australia to defend the country from attack.

The AIF initially consisted of one infantry division and one light horse brigade. The first contingent departed Australia by ship for Egypt on 1 November 1914, where it formed part of the Australian and New Zealand Army Corps (ANZAC). The infantry division fought during the Gallipoli Campaign between April and December 1915, reinforced by a second division which was later raised, as well as three light horse brigades. After being evacuated to Egypt the AIF was expanded to five infantry divisions, forming part of the I and II ANZAC Corps, which were committed to the fighting in France and Belgium along the Western Front in March 1916. Meanwhile, two mounted divisions remained in the Middle East to fight against Turkish forces in the Sinai and Palestine Campaign.

Later combined into the Australian Corps in 1917, the AIF divisions in France and Belgium were often used to spearhead operations, playing a significant role in the defeat of the German Army in 1918. By the end of the war the AIF had gained a reputation as a highly effective military force. Following the armistice on 11 November 1918, a process of demobilisation began, with the last Australian personnel being repatriated in late 1919. In all, 416,809 Australians enlisted during the war and 334,000 served overseas. The AIF sustained approximately 210,000 casualties, of which 61,519 were killed or died of wounds, a casualty rate among the highest of any belligerent for the war.

Background

The Commonwealth of Australia was founded on 1 January 1901. On 1 March, 29,010 colonial soldiers, consisting of 1,544 professional soldiers, 16,105 paid militia and 11,361 unpaid volunteers, were transferred to the new Australian Army. However, the units continued to be administered under the various colonial Acts. Major General Sir Edward Hutton, a former commander of the New South Wales Military Forces, was appointed as the first commander of the Commonwealth Forces, assuming command in early 1902 with Army Headquarters subsequently formed at Victoria Barracks in Melbourne. The Defence Act 1903 brought all of the state units under one piece of legislation; although more significantly, it prevented the raising of standing infantry units, only allowing the establishment of permanent administrative and instructional staff for headquarters, garrison artillery, fortress engineers, submarine mining engineers, and service, medical and ordnance units. It also stipulated that the force could only be maintained by voluntary enlistment and that it could not serve outside Australia. In this it effectively established the pre-eminence of the Citizen Forces, ensuring that the Australian Army would primarily consist of part-time militia and volunteer forces, which would be supported by a small permanent force limited to filling staff, training and garrison roles. It equally ensured that any force sent overseas could only be done so on a voluntary basis.

Yet despite significant reorganisations of the post-Federation Army in 1903 and 1906, the force-in-being was increasingly seen as dysfunctional and inadequate, suffering from perceived institutional problems regarding structure, command, and administration, as well as limited financial resources, lack of modern equipment, and poor training. In time this led the government to decide to adopt an entirely new military system. In 1911, two significant changes followed a report by Lord Kitchener following his inspection of local forces in 1909. The Royal Military College, Duntroon was established to train staff officers, and a system of universal national service began with boys aged 12 to 18 becoming cadets, and men aged 18 to 26 serving in the Citizen Forces. These reforms were part of a process of raising a large civilian militia to defend the country against a feared attack by Japan. This force was based on conscription, and was intended to be complete in 1920. The resources devoted to this plan greatly exceeded those allocated to preparations to raise an expeditionary force to serve outside Australia. In total, a peacetime force of around 80,000 citizen soldiers, with a wartime establishment of 135,000, was to be raised and would include 84 infantry battalions (later increased to 92), 28 light horse regiments (subsequently raised to 31), 49 field batteries and seven howitzer batteries (total of 224 guns), 14 field engineer companies, seven communication companies, and various support troops.

This force was to be organised into brigades, with no divisional headquarters raised, although it was envisioned that up to six divisions could be formed if required. The infantry was planned to be organised into 21 brigades (later 23) of four battalions each, while the light horse would initially form seven brigades (later eight). The field artillery would be organised into 14 brigades, while eight of the field batteries would be attached to the light horse brigades, and the howitzer batteries would not be brigaded. A small permanent force of 3,200 men would operate in support. The new scheme also entailed reorganisation of the military districts, with the 1st Military District based on Queensland, the 2nd on New South Wales, the 3rd on Victoria, the 4th on South Australia, the 5th on Western Australia and the 6th on Tasmania. The Northern Territory and New Guinea were not initially allotted, but were later incorporated into the 1st Military District.

Steps had also been taken to expand the pre-Federation network of coastal defences to provide protection against raids from Japanese or German warships prior to World War I. In 1912, these defences were manned by 14 companies of the Australian Garrison Artillery, each of which had a strength of over 100 men. Meanwhile, in September 1912 the government officially approved the formation of an Australian military air arm. In so doing Australia became the first of the Dominions, and one of the few nations outside of Europe, to begin to develop such a capability, even if it was initially only a modest one. The Central Flying School was established at Point Cook, Victoria in 1913. Flying training did not begin immediately, though, and it was not until 1914, that the first class of pilots were accepted. No. 1 Flight of the Australian Flying Corps was raised in the 3rd Military District on 14 July 1914.

Following Britain's declaration of war on Imperial Germany on 4 August 1914 at the outbreak of the World War I, Australia and the other members of the British Empire were automatically involved, with Prime Minister Joseph Cook stating on 5 August that "...when the Empire is at war, so also is Australia." Within days, Brigadier General William Bridges and his staff officer, Major Brudenell White, had completed plans for the creation of the Australian Imperial Force (AIF). White proposed an expeditionary force of 18,000 men, including 12,000 Australians and 6,000 New Zealanders. Cook subsequently approved the proposal, although he increased the offer to 20,000 men to serve in any destination desired by the British government. On 6 August 1914, London cabled its acceptance of the force and asked that it be sent as soon as possible. Recruiting offices opened on 10 August and by the end of 1914, 52,561 volunteers had been accepted, despite strict physical fitness guidelines. Meanwhile, after an additional British request for assistance on 6 August 1914, the Australian government hurriedly prepared another expeditionary force, known as the Australian Naval and Military Expeditionary Force (AN&MEF), to destroy the German wireless stations at Yap in the Caroline Islands, Nauru, and Rabaul in New Britain.

Organisation

Home Army

Despite some progress, by 1914 the Citizen Forces were still incomplete, numbering approximately 45,915 men, with many units still to be raised. During the precautionary stage on 2 August 1914 prior to the outbreak of war, Citizen Forces units were called up to guard key infrastructure and essential points and man coastal forts and harbour defences. Militia fortress companies assisted the permanent artillery and engineers in manning defence electric lights at Port Jackson, Port Phillip, Fort Lytton, Fremantle and on the Derwent River. All coastal defence batteries were activated hours before the declaration of war against Germany (which took place at 9:00 am Melbourne time on 4 August). The next morning the first Allied shots of the war were fired by the garrison at Fort Nepean, which was located at the opening of Port Phillip Bay, after the examination battery there fired a shell over the bows of the German cargo ship SS Pfalz when the ship failed to stop.Wells, Samuel Garnet (1914), "Preparatory sketch of Australians firing at the German steamer Pfalz which attempted to get through the Melbourne heads on 4th (sic) August 1914", pencil drawing in the collection of the National Library of Australia."German Vessel Stopped: Incident at Queenscliff: Guard of Marines placed on Board", The Brisbane Courier, (6 August 1914), p. 8."First shot in the War", The (Launceston) Examiner, (16 March 1940), p. 12. In accordance with pre-war plans mines were ready to be laid by the Royal Australian Engineers to protect Port Jackson and Port Phillip; however, the risk of attack was not considered sufficient to justify the establishment of the minefields and their ongoing maintenance.

After the initial call-up of reservists to man the garrison artillery, the commanding officers of the other militia units were directed to begin preparations to raise an infantry division and a light horse division for home defence tasks. By the end of August 1914 the Government had judged that a force of this size was unnecessary given that Australia was distant from the war zones. Instead, it was decided to maintain only a small number of infantry battalions and light horse regiments on active duty at any one time. By the end of 1914 the home defence force comprised 100,000 reservists, of whom 56,000 were members of the Citizen Forces and 51,000 were rifle club volunteers. Despite fears of sabotage and uprisings by German-Australians, no domestic threat eventuated. From 1915, only skeleton garrisons were maintained at coastal forts, but the personnel manning them were forbidden to enlist in the AIF. This ban was lifted in April 1915 but the presence of a German commerce raider in Australian waters caused a mobilisation from February to April 1916, while another occurred in April 1918 for the same reason. In June 1918, 9,215 home service troops were on active duty in Australia, alongside 2,476 regular soldiers. Up to 50,000 militiamen enlisted in the AIF during the war.

Australian Naval and Military Expeditionary Force