Raised in April 1941, the brigade consisted of Militia units who were assigned to carry out defensive duties on the New South Wales Central Coast.

After being mobilised for war in December 1941, the brigade mounted defensive duties throughout 1942 and 1943, defending against a possible Japanese invasion.

Upon formation, the brigade was assigned several part time Militia units – the 34th and 45th Battalions, and the Sydney University Regiment[1] – and was assigned a defensive role around the Wollongong and Port Kembla areas, taking over from the 14th Brigade in this role.

At this time, the brigade's area of responsibility stretched north from Drummond and Balgownie to cover Wollongong and Port Kembla, to Loftus, to provide cover to Port Hacking and Cronulla, south of Sydney.

The 19th Battalion was detached to support the Combined Overseas Training Centre at Gan Gan,[2] although it was later transferred to the 6th Brigade in April 1943 as part of an Army-wide reorganisation to create nine full strength divisions.

During this time, the brigade came under the direct command of the Second Army, although it was returned to the 1st Division, which was headquartered around Parramatta.

[5] The latter half of 1943 was relatively stable for the brigade, although the 34th Battalion moved to Rutherford in August, having been detached to Gateshead in March.