The initial phase saw the Australians advance towards the Hongorai River . Following the end of the early fighting , the Australian advance towards the main Japanese concentration at Buin continued as they struck out towards the Hari and Mivo Rivers . This continued until torrential rain and flooding brought the advance to a halt short of the objective , washing away many bridges and roads upon which the Australians relied for supplies . As the Australian advance stalled , the Japanese began harassing the Australian line of communications , and as the rain stopped and the flooding subsided in late @-@ July and into August , the Australians began making preparations to resume the advance towards Buin again . Ultimately , though , the war came to an end before the final Australian advance began , bringing the campaign to an end .