Involving forces from Australia, the United States, and Japan, the fighting centred on a high feature south of the village of Efogi on the Kokoda Track.

Together with elements of the armed Papuan Constabulary – who were used mainly to maintain order amongst the native carriers that were conscripted into carrying supplies and evacuating the wounded[9] – ANGAU, and two detachments from the 2/6th and 14th Field Ambulances, the Australians had a force of 1,400 men at the start of the battle.

[14] Strung out, with gaps between the positions, this represented a significant weakness, which the Japanese commander, Colonel Masao Kusunose,[15] in charge of the 144th Infantry Regiment, sought to exploit.

[17] While the Japanese began moving into position north of Mission Ridge in preparation for the main attack, Allied aircraft carried out an air raid at Kagi on 6/7 September, killing two and wounding another two.

The following day, a force of eight US B-26 Marauders, escorted by four P-40 Kittyhawks, carried out a larger airstrike in support of the Australian ground troops on the track, killing eleven Japanese and wounding another twenty.

Co-ordination proved difficult with only intermittent wireless contact, and in the confusion the entire 2/27th fell back, effectively giving up the ridge to the Japanese.

[25] Despite reinforcement by a composite company of 95 to 110 men,[6][26] the Australians were unable to restore the situation and Potts was forced to order a withdrawal south towards Ioribaiwa.

Had the Japanese commander been fully aware of the situation, according to author Lex McAulay there was an opportunity to exploit the Australian weakness and potentially advance all the way to Port Moresby.

Amidst heavy rain, and with numerous stretcher cases and limited rations,[34] it took over three weeks for the 2/27th to marry back up with Maroubra Force, thus depriving the Australians of a relatively fresh infantry battalion for the final defensive battle at Ioribaiwa.

[6][16] For the Japanese, the supply situation was stretched even further as they continued their advance south, while the Australian resistance was rapidly stiffening, although weakened by the absence of the men from 2/27th.

[9] A week after the fighting around Mission Ridge and Brigade Hill, the Australians, under Porter, made another stand at Ioribaiwa after withdrawing through Menari and Nauro.

[9] Over the period 14 to 16 September, the II and III Battalions of the Japanese 144th Infantry Regiment attempted to outflank the Australian positions, but were rebuffed and fought to a standstill.

As their supply line became stretched, and resources were diverted to the fighting on Guadalcanal, Horii was told to assume defensive operations on 8 September, and he cancelled the offensive several days later.

From there the Australians began a counter-offensive, while elsewhere at Milne Bay they successfully prevented a Japanese landing from capturing several vital airfields in late August and early September.