The primary objective of Operation Doublet was to capture Mubo and link up with the Americans advancing from Nassau Bay. The Allies would then advance to Goodview Junction, Mount Tambu and the adjoining ridges down to the coast, but not beyond that line. Although Operation Doublet included attacks by the Americans on the coastal flank and 15th Brigade on the western flank, the proposed axis of advance would be that of 17th Brigade. Savige later wrote how his former brigade would be ‘my spearhead in the attack and my clenched fist to drive home success’.

Brigadier Moten had planned to commence the 17th Brigade operation against Mubo on 5 July but, due to the delays with Lieutenant-Colonel Taylor's US 1/162 Battalion moving inland from Nassau Bay, it was delayed until 7 July. Meanwhile the 2/5th Battalion moved up from Wau to participate in the operation. Three companies, A and B Companies from the 2/6th and C Company from the 2/5th, would take part in the first phase of the attack: to take Observation Hill overlooking Mubo. On the afternoon of 6 July Captain Jo Gullett took B Company down on to a small plain at the foot of Observation Hill where they gathered alongside Captain Mick Stewart's and Captain Bill Morse's companies. A rough hospital had been built by the natives, and a pile of wooden crosses sat nearby. ‘I hope they've sent enough,’ Lieutenant Ernie Price wryly observed.