At this time, the 30th Battalion was again attached to the 8th Brigade and undertook garrison duties in New South Wales. In March 1942, the 30th Battalion occupied defensive positions in North Sydney including beach defences to respond to possible Japanese landings at Manly, Freshwater Beach, and Curl Curl. Later the 30th was sent to Greta, where it concentrated with the rest of the 8th Brigade before being transferred to Western Australia. The 30th Battalion remained there until late 1943 when they were moved to Queensland to undertake training for possible deployment overseas. In early 1944, the units of the 8th Brigade were dispatched to New Guinea in support of the 9th Division which was taking part in the Huon Peninsula campaign. During this time, the 30th Battalion's most notable involvement came during the Battle of Sio. Further operations saw the battalion advance along the coast and occupy Madang and Alexishafen, before returning to garrison duties in the Madang–Hansa Bay area following the completion of the campaign. Later, in June 1945, the 30th Battalion was moved to Wewak where they provided a supporting role to the 6th Division’s campaign, conducting patrols around Mount Tazaki and Mount Shiburangu. During this time they were involved in a number of minor engagements with Japanese forces in the area, with the most notable coming in July when the battalion helped repel a Japanese attack on Australian positions around Mount Tazaki.