By 22 May , although it were still a number of Japanese in the area which continued to harass and ambush their line of communications , most of the Australian objectives had been secured and mopping up operations began . The last remaining defensive location before the Hongorai was Egan 's Ridge , where the Japanese were sheltering in tunnels . A heavy aerial and artillery bombardment devastated the position and forced them to abandon the ridge . It was subsequently occupied by a company of Australian infantry . Within a short period of time the Buin Road was subsequently opened , providing the Australians with the means with which to bring up supplies for the next stage of the campaign , being the advance to the Hari , Mobiai , and Mivo Rivers . The final phase of the battle cost the Japanese 106 killed , while the Australians lost 13 killed and 64 wounded .