 Australian and United States air units began their pre @-@ invasion attacks on north Borneo in late May . The first attack on the Brunei Bay area took place on 3 May , and included a raid targeting the town of Victoria on Labuan . A large number of further attacks were conducted to suppress Japanese airfields and other facilities throughout north @-@ western and north @-@ eastern Borneo . The plans for the invasion of Brunei Bay had specified that the landings would be supported by aircraft based at Tarakan , but delays in rebuilding the airfield there rendered this impossible and reduced the scale of the pre @-@ invasion bombardment . 
