The next phase of the campaign involved the advance of Australian forces along the coast towards Sio, about from Finschhafen. Following the capture of Gusika, the responsibility for the first part of the advance to Sio was taken over by the infantry of the 4th Brigade, under the command of Brigadier Cedric Edgar. They were brought forward from Finschhafen early in December where they had been undertaking garrison duties and on 5 December, the 22nd Infantry Battalion began the advance, crossing the Kalueng River. Lacking the experience that the 2nd AIF units had, the Militia battalions advanced more cautiously than they might otherwise have done so. They were supported by American landing craft equipped with rockets, which bombarded Japanese positions along the coast, while the expansion of the airfield around Finschhafen and the establishment of a naval facility there enabled the Allies to use Consolidated PBY Catalina aircraft and PT boats to further attack Japanese resupply efforts.