During the Second World War, the 28th undertook defensive duties in Australia for the majority of the conflict, before seeing action against the Japanese in the New Britain campaign in 1944–1945.

It remained on the Australian Army's order of battle until 1960 when it was subsumed into the Royal Western Australia Regiment, but was later re-raised in 1966 as a remote area infantry battalion.

[6] After completing rudimentary training, the 28th embarked on the transport Ascanius on 9 June and sailed from Fremantle to Egypt via the Red Sea.

[7] The 28th arrived in Egypt in July and concentrated along with the rest of the 7th Brigade at Abbassia, near Cairo, where they were assigned to the newly formed Australian 2nd Division.

Upon arrival the brigade was temporarily attached to the New Zealand and Australian Division as reinforcements, occupying positions north-east of Anzac Cove around "Cheshire Ridge".

[9][10] They remained on the peninsula for the next few months, manning the trenches, improving defences and defending the beachhead until the evacuation in mid-December, when they were withdrawn back to Lemnos Island.

[11] Casualties during the 28th's brief involvement in the campaign were described by the Australian War Memorial as "light",[1] and the battalion's strength on departing the peninsula was 24 officers and 667 other ranks.

[15] For the next two-and-a-half years, they would fight in the trenches of the Western Front in both Belgium and France and take part in numerous battles.

[1] In early 1917, the Germans began a surprise withdrawal along the front, which enabled them to hold the line with fewer troops, thus gaining a pool of reserves.

[20] A brief lull followed in June and July as the Allies attempted to regain the initiative, during which the 28th was involved in a minor action around Morlancourt.

It was there, on the first day of the offensive, that Lieutenant Alfred Gaby, performed the deeds that led to him becoming the 28th Battalion's first, and only, Victoria Cross recipient.

The following day, they forced their way across the river around Peronne,[1] and during the subsequent Battle of Mont St Quentin–Peronne, they joined the 7th Brigade's advance towards Aizecourt-le-Haut.

[31] Throughout the early part of the Second World War, the 28th Battalion undertook brief periods of continuous service,[29] providing training to recruits who were enlisted following the re-establishment of conscription in January 1940 to improve the nation's overall readiness.

After Japan's entry into the war, the 13th Brigade's units were mobilised for full-time service and pressed into home defence with III Corps, undertaking garrison duties to defend Western Australia against a possible invasion.

[29][33] Late in the war, the 13th Brigade was reassigned from the 4th Division to the 5th, and in November 1944 they were committed to the New Britain campaign, landing at Jacquinot Bay the following month and later established themselves around Waitavalo.

From then until the end of the war in August 1945, the 28th took part in a containment campaign against the much larger Japanese force on the island, as the Australians attempted to confine them to the Gazelle Peninsula and Rabaul.

This continued until October 1987, when the two companies were amalgamated to form the current 11th/28th Battalion, Royal Western Australia Regiment.