Arthur retained command of No. 78 Wing for the invasion of Tarakan, which commenced on 1 May. Augmented by No. 452 Squadron's Spitfires, the wing was a last-minute replacement for No. 81 Wing—which had been delayed while moving its aircraft forward from Noemfoor and northern Australia—and had only ten days to prepare for the operation. As well as its flying squadrons, No. 78 Wing's complement included No. 114 Mobile Fighter Control Unit (No. 114 MFCU), No. 29 Air Stores Park, No. 28 Medical Clearing Station, and No. 11 Repair and Servicing Unit. On 25 May 1945, Arthur was succeeded by Wing Commander Alan Rawlinson. In June and July, the wing took part in the assaults on Labuan and Balikpapan, undertaking convoy escort in the former and, joined once more by No. 452 Squadron, ground-attack missions and close support of the Australian 7th Division in the latter. During July it flew 858 sorties, dropping over of bombs and expending almost 350,000 rounds of ammunition, for the loss of six aircraft and four pilots killed or missing.