Originally raised in April 1915 for service in World War I as part of the Australian Imperial Force (AIF), it was assigned to the 7th Brigade and consisted of personnel recruited from the states of Queensland, Tasmania and Victoria.

In mid-1916, it was sent to Europe where it served in the trenches of the Western Front in France and Belgium for the rest of the war, fighting in most of the battles that the Australians took part in between 1916 and 1918.

Later in the war, the entire 26th Battalion, along with the rest of the 11th Brigade, was committed to the Bougainville campaign where they saw action against the Japanese from late 1944 until the end of hostilities in August 1945.

[3] With an authorised strength of 1,023 men,[1] after a short period of basic training, the battalion's first draft – consisting of two companies of Queenslanders – embarked for overseas in May.

In early June, alongside the 28th Battalion, they took part in the first raid undertaken by Australians in France, attacking German trenches around Bois Grenier.

[9] Their first major battle came around Pozières between July and August, after which the battalion was sent along with the entire 2nd Division to a quieter sector in Belgium having suffered over 650 casualties.

Christmas was spent in the trenches around Amiens,[12] but in early January 1917, the 26th Battalion was transferred to the Ancre Valley and then to Le Sars later in the month.

[3] During the fighting around Lagnicourt, Captain Percy Cherry led his company into the village, capturing several positions before helping to hold off several German counterattacks; he was later awarded the Victoria Cross posthumously.

[17] In April 1918, after the Allies had been pushed steadily back, the 26th Battalion was transferred from the Messines sector south to the Somme and committed to the fighting along with other Australian units.

The 26th undertook defensive tasks throughout April and May in various locations including Baizieux, Camon and Ribemont, during which time over 100 casualties were suffered before the German offensive was eventually halted.

[18] After this, throughout June and July the battalion launched a number of "peaceful penetration" operations to take small amounts of the German front line during the lull that followed prior to the final Allied offensive of the war.

In 1929, following the election of the Scullin Labor government, the compulsory training scheme was abolished and replaced with an all volunteer force known as the "Militia".

Upon re-forming, the battalion was placed under the command of one of the Australian Army's most decorated soldiers, Lieutenant Colonel Harry Murray, a World War I Victoria Cross recipient.

[33][34] Following the outbreak of World War II in September 1939, the 26th Battalion undertook a series of training camps around northern Queensland as it began to re-establish its numbers.

Between September and November, it was based around Kissing Point, Queensland, before moving to Townsville in February 1940, and then south of Bowen the following month.

[33][34] Many of the initial recruits came from Italian-Australian families from north Queensland,[29] but as the battalion grew, reinforcements from other Australian states arrived during 1942 and early 1943.

[33][35] Throughout 1941 and 1942, the battalion undertook defensive duties in various locations around Queensland, including Charters Towers, Bohle River, and Alligator Falls.

'A' Company was detached at this time to Merauke Force in the Dutch East Indies, becoming the first Militia unit to serve outside of Australian territory.

Between August 1943 and November, defensive duties were undertaken on the mainland around the Cape York Peninsula, before the battalion returned to Horn Island.

[36][35] In July 1944, the 26th Battalion was withdrawn to Australia on board the transport Taroona, and after leave reconstituted at Strathpine, Queensland, and began training for further operations.