The campaign that Australian planners developed entailed three separate drives : in the north , it was planned that Japanese forces would be forced into the narrow Bonis Peninsula and contained ; in the centre the seizure of Pearl Ridge would give the Australians control of the east – west avenues of approach , as well as affording them protection against further counter @-@ attacks , while also opening the way for a drive to the east coast ; and the main campaign in the south , where the bulk of the Japanese forces were concentrated around Buin .