The Kokoda Track campaign or Kokoda Trail campaign was part of the Pacific War of World War II. The campaign consisted of a series of battles fought between July and November 1942 between Japanese and Allied—primarily Australian—forces in what was then the Australian territory of Papua. Following a landing near Gona, on the north coast of New Guinea, on the night of 21/22 July, Japanese forces attempted to advance south overland through the mountains of the Owen Stanley Range to seize Port Moresby as part of a strategy of isolating Australia from the United States. Initially only limited Australian forces were available to oppose them, and after making rapid progress the Japanese South Seas Force under Major General Tomitaro Horii clashed with under strength Australian forces from the Papuan Infantry Battalion and the Australian 39th Battalion on 23 July at Awala, forcing them back to Kokoda. Following a confused night battle on 28/29 July, the Australians were again forced to withdraw. The Australians attempted to recapture Kokoda on 8 August without success which resulted in heavy casualties on both sides, and the 39th Battalion was subsequently forced back to Deniki. A number of Japanese attacks were subsequently fought off by the Australian Militia over the following week, yet by 14 August they began to withdraw over the Owen Stanley Range, down the Kokoda Track towards Isurava.
The Japanese failed to press their assault, however, and the next 10 days proved to be a respite for the Australians. Reinforcements, including the 53rd Battalion and the headquarters of the 30th Brigade under the commander of Brigadier Selwyn Porter, arrived to bolster the Australian forces, while the 21st Brigade under Brigadier Arnold Potts also arrived at Isurava by 23 August. The Australians faced significant supply issues despite the modest size of their forces, and the 39th Battalion was subsequently withdrawn to ease the logistic burden. The Japanese advance resumed on 26 August, forcing Potts to mount a series of delaying actions as the 21st Brigade successively fell back, first to Eora Creek on 30 August, Templeton's Crossing on 2 September, and Efogi three days later on 5 September. However, the Japanese were now increasingly hampered by supply problems of their own as they became overextended, while the Australian defence also became better organised. Regardless, the effectiveness of the Australian units was increasingly reduced through exhaustion and sickness from operating in the harsh terrain.
On 10 September, Potts handed over command to Porter, who was subsequently forced to withdraw to Ioribaiwa. The Japanese unsuccessfully mounted a further attack the following day, as they began to run out of momentum against the Australians who began to receive further reinforcements, including brigades from the experienced Australian 7th Division under the command of Major General Arthur Allen. The 25th Brigade under Brigadier Kenneth Eather took over the forward area on 14 September. Heavy fighting continued around Ioribaiwa for the next week, however, and the Australians were again forced to withdraw on 17 September, this time to Imita Ridge, in sight of Port Moresby itself. Having outrun his supply lines and following the reverses suffered by the Japanese at Guadalcanal, Horii was now ordered on to the defensive, marking the limit of the Japanese advance southwards. The Japanese subsequently began to withdraw on 24 September to establish a defensive position on the north coast, but they were followed by the Australians under Eather who recaptured Kokoda on 2 November. Further fighting continued into November and December as the Australian and United States forces assaulted the Japanese beachheads, in what later became known as the Battle of Buna–Gona.