In February 1943, with the passing of the "Defence (Citizens Military Forces) Act 1943", the role of the Militia was clarified with the Act expanding the geographical area in which such units could be deployed to include all of New Guinea and parts of the Netherlands East Indies, Borneo and the Solomon Islands. The following month, under the command of Lieutenant Colonel Kenneth Cusworth—who would serve as the battalion's commanding officer throughout its existence—the battalion was sent to New Guinea, along with the rest of the 4th Brigade, to reinforce the garrison at Milne Bay, where units from the 7th Brigade had turned back a Japanese landing the previous year.