The Papuan Infantry Battalion (PIB) was a unit of the Australian Army raised in the Territory of Papua for service during the Second World War. Formed in early 1940 in Port Moresby to help defend the territory in the event of a Japanese invasion, its soldiers were primarily Papuan natives led by Australian officers and non-commissioned officers. Following the outbreak of the Pacific War, the PIB served in many of the Allied campaigns in New Guinea; however, due to the nature of its role its sub-units mainly operated separately, attached to larger Australian and US Army units and formations. Slow in forming, the first members of the PIB were not officially posted in until March 1941. By 1942 it consisted of only three companies, all of which were under-strength and poorly equipped. It was subsequently employed on scouting, reconnaissance and surveillance patrols against the Japanese, where the natural bushcraft of its native soldiers could be used to their advantage. The PIB was sent forward in June 1942 to patrol the northern coast of Papua and was dispersed over a wide area. These small parties were the first to make contact with the Imperial Japanese forces upon their landing in Papua, before participating in the Kokoda Track campaign. As part of Maroubra Force, the PIB fought alongside the Australian 39th Battalion at Kokoda, Deniki, and Isurava as the Japanese forced them back along the Kokoda track, but was withdrawn before the campaign finally turned in favour of the Australians.

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 in what was then the Australian Territory of Papua. It was primarily a land battle, between the Japanese South Seas Detachment under Major General Tomitarō Horii and Australian and Papuan land forces under command of New Guinea Force. The Japanese objective was to seize Port Moresby by an overland advance from the north coast, following the Kokoda Track over the mountains of the Owen Stanley Range, as part of a strategy to isolate Australia from the United States.