The battle of Buna–Gona was part of the New Guinea campaign in the Pacific Theatre during World War II. It followed the conclusion of the Kokoda Track campaign and lasted from 16 November 1942 until 22 January 1943. The battle was fought by Australian and United States forces against the Japanese beachheads at Buna, Sanananda and Gona. From these, the Japanese had launched an overland attack on Port Moresby. In light of developments in the Solomon Islands campaign, Japanese forces approaching Port Moresby were ordered to withdraw to and secure these bases on the northern coast. Australian forces maintained contact as the Japanese conducted a well-ordered rearguard action. The Allied objective was to eject the Japanese forces from these positions and deny them their further use. The Japanese forces were skillful, well prepared and resolute in their defence. They had developed a strong network of well-concealed defences.

Operations in Papua and New Guinea were severely hampered by terrain, vegetation, climate, disease and the lack of infrastructure; these imposed significant logistical limitations. During the Kokoda Track campaign, these factors applied more-or-less equally to both belligerents but favoured the defender in attacks against well-fortified positions. The battlefield and logistical constraints limited the applicability of conventional Allied doctrine of manoeuvre and firepower. During the opening stages of the offensive, the Allies faced a severe shortage of food and ammunition. This problem was never entirely resolved. The battle also exposed critical problems with the suitability and performance of Allied equipment. The combat effectiveness of US forces, particularly the US 32nd Division, has been severely criticised. These factors were compounded by repeated demands from General Douglas MacArthur, Supreme Commander of Allied Forces in the Southwest Pacific Area, for a rapid conclusion to the battle. The demands were more to politically secure MacArthur's command than for any strategic need. In consequence, troops were hastily committed to battle on repeated occasions, increasing Allied losses and ultimately lengthening the battle.

Allied air power interrupted the Japanese capacity to reinforce and resupply the beachheads from Rabaul. This ultimately made the Japanese position untenable. There was widespread evidence of the Japanese defenders cannibalising the dead. In the closing stages of the battle, significant numbers of the defenders were withdrawn by sea or escaped overland toward the west and the Japanese base around Salamaua and Lae. The remaining garrison fought to the death, almost to the man.

The resolve and tenacity of the Japanese in defence was unprecedented and had not previously been encountered. It was to mark the desperate nature of fighting that characterised battles for the remainder of the Pacific war. For the Allies, there were a number of valuable but costly lessons in the conduct of jungle warfare. Allied losses in the battle were at a rate higher than that experienced at Guadalcanal. For the first time, the American public was confronted with the images of dead American troops.