The Japanese had landed at Lae and Salamaua in March 1942. A year of setbacks followed — Coral Sea, Kokoda, Milne Bay, Buna-Gona. By late January 1943 Japan's last serious lunge, toward the Wau airfield, had been turned back by Australians flown in as reinforcements. The Okabe Detachment retreated toward Mubo, losing roughly 1,200 men to starvation on the withdrawal alone. Brigadier Murray Moten's 17th Brigade followed up. In March, commandos of the 2/7th Independent Company began harassing the Japanese around Mubo while the 2/5th Battalion moved onto Guadagasal Ridge. The Allied bombers hit the approaches. The Battle of the Bismarck Sea sank Japanese reinforcements before they arrived. The ground force at Mubo was, nevertheless, reinforced by marines of the Maizuru Special Naval Landing Party, and the fighting shifted from harassment to something that looked, on paper at least, like a conventional offensive.

On 24 April, Moten threw his 2/7th Battalion at the Pimple. Douglas A-20 Bostons bombed first; they did not noticeably soften the target. A feint up the main track pinned itself down; the flanking platoon hit a previously unknown Japanese machine-gun position and was cut to pieces. Six killed, eight wounded on day one. Three more wounded on day two. A second attempt on 2 May, with mountain guns this time, also failed. On 9 May, about 500 Japanese troops from the 102nd and 115th Regiments counterattacked. They fell on an isolated company under Captain Leslie Tatterson, positioned north of the main Australian line. Over several days, Tatterson's men absorbed eight separate assaults before a relief force of 60 men broke through on 11 May. Australian losses were 12. Japanese losses were 100. The Pimple and Green Hill, however, remained Japanese.

If the Pimple could not be taken, perhaps Mubo could be turned. On 5 July, the 1st Battalion of the U.S. 162nd Infantry Regiment, just landed at Nassau Bay under Lieutenant Colonel Harold Taylor, was ordered to occupy Bitoi Ridge and squeeze the Japanese from behind. The Americans were slow off the beach; their lead company reached the ridge crest but could not break the Japanese hold on Mubo. Attention returned to frontal assault. The 2/6th Battalion pushed forward from Wau. Beginning on 7 July, Australian and American artillery combined with fresh infantry attacks on Observation Hill, the Pimple, and Green Hill. The Japanese commander, Hidemitsu Nakano, had already made his decision. On 10 July he ordered withdrawal to the Komiatum area south of Salamaua. By 12 July, Mubo was secure. A blocking force arrived on the night of 12-13 July, a day too late to trap the retreating Japanese, who fell back to Mount Tambu.

Over 950 Japanese soldiers had been killed in the joint Allied advance of early July. The Australian Army awarded two battle honours for Mubo: Mubo I to the 2/7th for the attacks between 22 April and 29 May, Mubo II to the 2/5th and 2/6th for the capture of the village between 7 and 14 July. The whole point of the battle, in the end, had been to keep Japanese attention fixed on Salamaua while the real Allied objective, Lae, was prepared for assault. Salamaua fell on 11 September, four days before the airborne landings at Nadzab made the Japanese position at Lae untenable. Mubo had done exactly what it was supposed to do, at the cost of three months and a great many men whose names do not appear in this account.

The village of Mubo still exists, a small community in Morobe Province reached by jungle track from the coast. Lababia Ridge, about two kilometers southwest, is where the 2/7th dug in during late June — that fight became its own named battle. Observation Hill, the Pimple, Green Hill, and the tracks connecting them are now part of a landscape more visited by ornithologists than by historians. Remains of Japanese equipment still turn up occasionally. The jungle reclaims everything on a fast schedule here, but it does not quite erase. A hundred yards of cleared ridgeline, from the right angle, still shows the shape that made it worth fighting over.