Raised in July 1940 and consisting of three infantry battalions, the 25th Brigade initially served in the United Kingdom, where it formed part of the garrison tasked with defending against a possible German invasion.

[1] The brigade was created following the Fall of France, initially as a temporary formation that would defend southern England, in the event of an invasion by German forces.

[2] It had an foundational establishment of 1,759 personnel; a majority were drawn from service support corps of the 6th Division, although roughly a quarter of this number were diverted from infantry reinforcements bound initially for AIF units in the Middle East.

[3] Upon arrival, the brigade was sent to Palestine, although it moved to Ikingi Maryut, in Egypt, in April 1941 as preparations were made to deploy to Greece, in support of the 6th Division.

However, in response to German moves in North Africa, the brigade was deployed to Mersa Matruh in the Western Desert, remaining there until relieved in May.

The campaign was short, but hard fought and the brigade's major actions during this time included an attack on Merdjayoun and fighting around Jezzine.

As the fighting between Japanese and Australian forces along the Kokoda Track intensified, the brigade received orders to deploy to New Guinea, and they subsequently arrived in Port Moresby in September 1942.

After heavy fighting, a withdrawal was undertaken to Imita Ridge, and by the end of the month the Japanese advance towards Port Moresby had reached its limit.

[13] Following the capture of Lae, the brigade was flown to Kaiapit and the took part in the advance through the Finisterre Range, culminating in the Battle of Shaggy Ridge.

The Japanese surrendered in August 1945, after which the brigade served as occupation troops in Dutch Borneo until civilian authorities could be re-established.