Imita Ridge, only a short distance from Port Moresby, ultimately proved to be the limit of the Japanese advance south. Having exhausted their supply line, which was increasingly being interdicted by US and Australian aircraft, and as events elsewhere, particularly Guadalcanal, coupled with the earlier defeat around Milne Bay, turned in favour of the Allies, the Japanese were forced into adopting a more defensive posture in New Guinea. Instead of a final stand, the fighting around Imita Ridge petered out into a series of small-scale patrol actions, before the Japanese began withdrawing north, beginning on 26 September. The remnants of the Australian 21st Brigade were led south by Porter, while the Australians, bolstered by the arrival of fresh troops from the 25th Brigade, launched a counter-attack under Eather, who officially assumed command of Maroubra Force on 17 September.