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 conducted by Australian and United States forces against the Japanese beachheads at Buna, Sanananda and Gona.
The Japanese forces at the start of the Battle of Buna–Gona had an effective strength of 5,500 or 6,500 after the landing of reinforcements on the night of 18 November 1942. The total force at the start of the battle is estimated at 9,000 and included several hospitals, their patients and labour units from the army and navy. The Japanese defensive positions at Buna, Gona and forward at the Sanananda track junction had been strongly developed before the arrival of the Allied forces. They have been described as some of the strongest encountered by the Allies in the course of the war. They made excellent use of terrain, which limited the tactical possibilities for attackers and consisted of hundreds of bunkers and machine gun emplacements developed in depth.
Many survivors of the Kokoda campaign congregated to the west near the mouth of the Kumusi River and linked up with Japanese reinforcements that were landed there in early December. This force actively threatened the western flank of the Australians at Gona. Sources give the total of Japanese forces deployed to Buna–Gona or operating to the west in the vicinity of the Kumusi and Membare Rivers as between 11,000 and nearly 12,000.
In mid December, there was nearly 10,000 deployed at the beachhead positions. Just before the fall of Sanananda and the battle ended, 1,200 wounded were evacuated by submarine. Estimates indicate a similar number were able to escape overland. Only about 250 prisoners were taken. The remainder, some 7,000 to 8,000, were killed.
Defences
Before the Allied forces arrived on the Buna–Gona coast, Richard K. Sutherland, then major general and chief-of-staff to General Douglas MacArthur, Supreme Commander of Allied Forces in the Southwest Pacific Area, had "glibly" referred to the Japanese coastal fortifications as "hasty field entrenchments." After the battle, Lieutenant General Robert Eichelberger, Commanding General US I Corps, called the Japanese utilisation of terrain "perfect" and "brilliant". Natural obstacles were used to advantage to channel attackers into coordinated fields of fire. The Japanese defensive positions at Buna–Gona have been described as "one of the most impressive defensive networks seen in the entire war." They consisted of hundreds of bunkers and machine gun emplacements. The positions had been skilfully developed in accordance with the principles of defence. They made excellent use of terrain, which limited the tactical possibilities for attackers. The defences were developed in depth. Individual positions were mutually supporting and alternative positions were used to confound attackers.
Maximum use was made of locally available resources. Concrete and steel was also used to a limited extent. A typical structure was revetted with coconut logs, reinforced with 44-gallon (55 US gal) drums filled with earth or concrete. The roof was made from two or three courses of logs, covered with earth. Ammunition boxes filled with earth and used rice bags were also common in construction. Most of the structure was built above ground due to the shallow water table. The complete structure might be above ground level. A large proportion had been constructed well in advance of the battle and were extremely well camouflaged by jungle regrowth which quickly covered them. Entrances were designed to protect the occupants from grenade blasts.
Structures were connected by a system of crawl trenches, with firing positions in between. The bunkers were mainly intended to protect the defenders from artillery and air attack. When the threat lifted, the defenders would disperse to firing positions between the bunkers and emplacements. The War Diary of the 2/6th Independent Company recounts: