Although it was raised late in the war the battalion would ultimately serve in a number of the Allied campaigns in New Guinea, including during the offensives on New Britain and Bougainville. After forming in the Markham Valley, the battalion concentrated at Camp Diddy, located near Nadzab in August 1944, where they were formed into several rifle companies, which were supported by a depot company for training purposes. In November 1944, the PIB along with the 1st and 2nd New Guinea Infantry Battalions were amalgamated to form the Pacific Islands Regiment. Further units would later be raised as the role of New Guinea troops was to be expanded. The 3rd and 4th New Guinea Infantry Battalions joined the Pacific Islands Regiment in 1945, although 4 NGIB was soon disbanded. A further battalion, the 5th New Guinea Infantry Battalion—although authorised—was never raised.