[1] These units continued to exist on the Army's order of battle throughout the war years,[2] within Australia, and separate from the deployed First Australian Imperial Force (AIF).

[3][4] In May 1940, the 20th Brigade was re-raised as part of the all volunteer Second Australian Imperial Force (2nd AIF), opening its headquarters at Ingleburn, New South Wales on the 7th of the month.

During the withdrawal, the 2/15th Battalion's headquarters was surrounded and captured after attempting to fend off an attack by German tanks,[8] while the 2/13th fought a more successful delaying action around Er Regina.

In early 1942, the Australian government sought the return of the 6th and 7th Divisions to Australia to meet the threat posed by Japan's entry into the war.

During this time, the 20th Brigade took over from the 18th, with forces spread out in the northern border region between Aleppo, Latakia, Idlib and Afrine, guarding against a potential German invasion through Turkey.

They subsequently helped halt the Axis advance during the First Battle of El Alamein, and then occupied defensive positions for the next four months.

A period of leave followed, after which the 20th Brigade was reconstituted at Kairi, Queensland, where training was undertaken to prepare for deployment to New Guinea.

Amphibious warfare training was undertaken during this time, as the division was assigned to an operation to capture Lae, which commenced in early September 1943.

A preliminary move was made from Cairns to Milne Bay, after which the 20th Brigade landed on the coast 16 miles (26 km) east of Lae.

Landing at Scarlet Beach, 10 kilometres (6.2 mi) north of the objective, the 20th Brigade formed the division's lead assault element.

[14][15] After this, reinforcements from the 9th Division arrived and the brigade's headquarters was moved to Heldsbach while elements were deployed at Simbang, Timoro, Kumawa and Jivevaneng.

The Japanese launched a strong counterattack on Scarlet Beach in October, during which the 2/17th was isolated around Jivevaneng; the 2/13th was subsequently moved from Katika to fight their way through to the 2/17th, after which the brigade began pushing towards Sattelberg.

In December, the 20th Brigade resumed the advance from Masaweng River, moving along the coast as the Australians pushed towards Sio, which they reached in January 1944.

These continued until the end of the war when occupation duties saw the brigade oversee the surrender of the Japanese forces that remained in Brunei and Sarawak.

After moving to Chermside, the remaining personnel undertook administration duties to return stores and equipment and complete necessary documentation prior to disbandment.