Between 1948 and 1965 the battalion was re-raised and disbanded a number of times before eventually becoming part of the Royal South Australia Regiment.

[6] After a period of basic training, the battalion embarked for the Middle East on the troopship HMAT A2 Geelong on 31 May 1915,[7] arriving there on 6 July.

[8] They then undertook a further two months of training in Egypt before an urgent request for reinforcements led to them being dispatched to join the Gallipoli campaign; they landed at Anzac Cove on 12 September.

Attached to the 7th Brigade, along with the 25th, 26th and 28th Battalions,[6][9] they reinforced the battle-worn New Zealand and Australian Division and took up a defensive position on Cheshire Ridge.

On 8 July 1916, the 7th Brigade was ordered to march to the Somme to support the Australian 1st Division which was taking part in the fighting around Pozières.

Moving off from positions around La Boiselle in the afternoon, the battalion advanced with two companies forward and two back in reserve under the cover of an intense artillery barrage.

[21] In early October, the battalion undertook a number of small scale raids on the German line, capturing a number of prisoners, before they were withdrawn from the line on 27 October and transferred back to the Somme where they subsequently took part in two unsuccessful attacks against German positions east of Flers.

[22] Offensive operations during this time were largely curtailed by bad weather, but on 2 March the battalions of the 5th and 7th Brigades launched a combined attack north of Warlencourt.

[22] The initial assault yielded some ground, but the Germans completed a successful outflanking move on the left, which threatened to take the momentum out of the attack.

[24] The 27th Battalion did not undertake a major engagement until 20 September when they took part in the Battle of Menin Road, which resulted in success for the Australians.

[28] At the end of January the brigade was relieved and moved back to Henneveux where it was tasked with covering a 24-mile (39 km) length of the line.

As the German offensive became focused upon Villers–Bretonneux they were called upon to undertake a supporting role to the Australian counterattack,[32] relieving the 6th Brigade around Ville-sur-Ancre following the 6th's assault on the town.

[30] They had been severely depleted and were suffering from acute manpower shortages as a result of the combination of a decrease in the number of volunteers from Australia and the decision to grant home leave to men who had served for over four years.

The process took a considerable period of time, though, and a large number of men were able to undertake tertiary and vocational training in England and France to prepare for their return to civilian life.

[6][Note 3] A total of 16 battle honours were awarded to the 27th Battalion for its involvement in the fighting on Gallipoli and the Western Front.

A year later, following the election of the Scullin Labor government, the compulsory training scheme was abolished and in its place a new system was introduced whereby the Citizens Forces would be maintained on a part-time, voluntary basis only.

[52] The 27th Battalion, however, did not suffer this fate and in 1938 it adopted the territorial title of "South Australian Scottish Regiment"[45] and was afforded the right to wear the MacKenzie tartan, after forming an alliance with the Seaforth Highlanders.

[57] In late May 1944, the 27th Battalion was shipped to Lae, before proceeding to Wau where it underwent further jungle warfare training while waiting for the American troops to established footholds on its way to Bougainville.

[58] The battalion was deployed to Green Island, in September 1944, relieving the American troops defending Lagoon Airfield.

Over the course of six weeks, the battalion carried out a number of minor attacks and in the process captured several key features before moving to the northern sector of the island on the Bonis Peninsula around Ratsua where they continued to harass Japanese forces through active patrolling and ambushing.

[48] Following the Japanese surrender, the 27th Battalion ceased operations and was transported to Torokina, where they had to wait for shipping to become available for repatriation back to Australia to begin the demobilisation process.

This process began in October 1945, albeit slowly, and gradually the battalion's numbers decreased as men were repatriated back to Australia or were transferred to other units for further service.

[Note 6] In addition to the normal campaign ribbons, the battalion's personnel also received a number of decorations for distinguished service and bravery, these included: one DSO, one MC, one MM and 16 MIDs.

[65] Following the introduction of the Pentropic divisional structure in early 1960, the CMF was reorganised and a number of infantry battalions were disbanded or amalgamated together to form six new State-based regiments.

The honours it inherited at this time were: North Africa; Syria 1941; The Litani; Sidon; Adlun; Damour; South-West Pacific 1942–1945; Kokoda Trail; Efogi–Menari; Buna–Gona; Gona; Liberation of Australian New Guinea; Ramu Valley; Shaggy Ridge; Borneo 1945; Balikpapan.