The Battle of Biak was part of the Western New Guinea campaign of World War II, fought between the United States Army and the Japanese Army from May 27 to August 17, 1944. Taking place on the island of Biak, in Geelvink Bay, in present-day Indonesia, it was part of General Douglas MacArthur's South West Pacific Area's offensive drive to clear New Guinea in preparation for an invasion of the Philippines. It was the first major effort by the Japanese to allow uncontested landings for the purpose of creating a kill zone inland. The main Allied objective was to capture the island so that they could construct airfields there. The battle resulted in the capture of the island by Allied forces, which were then used to support operations elsewhere in the Pacific.
Background The island of Biak forms part of the Schouten Islands, and dominates the entrance to Geelvink Bay, near the western end of New Guinea; its terrain and location about from Hollandia and from Sarmi (where the Japanese had begun concentrating supply bases and airfields), made it well suited to airfield construction, particularly in the flatter southeastern area. As a result, as the Allies began their advance towards the Philippines in 1944, General Douglas MacArthur's Southwest Pacific command began planning its capture.Smith 1996, p. 206 In conceptualizing the operation, Allied planners envisaged a week-long operation; estimating that there were up to 2,000 Japanese troops defending the area.Morison 2001, p. 107 Four landing beaches were chosen near Bosnek, designated Green 1, 2, 3 and 4. Allied planners considered these beaches to be poorer for landing operations, compared to those further away from the airfields, but they were chosen due to their proximity to the main Allied objectives and because aerial reconnaissance indicated that the beaches were not backed by cliffs or swamps, and that there were two jetties nearby that might facilitate deep-water port access.Smith 1996, pp. 282–285
The assault force consisted of five destroyer transports (APD), eight LSTs eight LCTs, and fifteen LCIs, supported by a myriad of smaller vessels including DUKWs, LCVPs and LVTs, which were chosen due to concerns about the coral reef opposite the landing beaches.Morison 2001, pp. 105–106 These were protected by two heavy cruisers, three light cruisers, and twenty-one destroyers;Smith 1996, pp. 284–286 several Australian vessels including the cruisers HMAS Australia and Shropshire and the destroyer Warramunga were included in this task force.Cassells 2000, p. 121Gill 1968, p. 422 The naval forces, designated Task Group 77.2, were commanded by Rear Admiral William Morrow Fechteler. Close air support for the Allied operation was provided by Lieutenant General George C. Kenney's Fifth Air Force, operating from Hollandia and Wakde Island, although elements of the Thirteenth Air Force, as well as Australian and Dutch squadrons operating from as far away as Darwin, also provided strategic air support.Smith 1996, p. 284
Allied intelligence greatly under-estimated the number of troops holding the island. The island was held by 11,400 Japanese troops under the command of Colonel Kuzume Naoyuki. Initially, the majority of the combat troops (about 4,000 personnel), were drawn from the veteran 222nd Infantry Regiment which had previously served in China, along with tanks from the IJA 36th Division, supported by artillery, anti-aircraft, construction and naval guard and base troops under Rear Admiral Sadatoshi Senda.Smith 1996, p. 300. These troops were reinforced by elements of the 35th Division's 219th and 221st Infantry Regiments.Smith 1996, pp. 355 & 359
Due to the size of the coastline he had to defend, and based on an appreciation of the Allied objectives, Kuzume focused his defensive plans away from the water's edge. Instead, he decided to carry out a feint, allowing the Americans to come ashore unopposed so that they would advance into the trap he had prepared for them utilizing a series of caves that were located west of Mokmer and to the east of Bosnek. This defensive complex was intended to turn the area around the vital airfield into a honeycomb of defended caves and pillboxes filled with riflemen, automatic weapons, artillery, batteries of mortars, and a single company of Type 95 Ha-Go light tanks. The western caves were connected by a series of underground tunnels and were largely constructed for fighting purposes. Kuzume also stockpiled these positions with ammunition and other supplies, with several dumps located around the eastern cave area, along with living quarters for the defenders.Smith 1996, pp. 300–301 Water was limited on Biak and had to be strictly rationed by the US troops, and heat and humidity would take a heavy toll during the fighting.US 41st Infantry Division 1944, p. 3
The Allies knew from an intercepted message dated 5 May 1944 that the IJA 2nd Area intelligence thought the next Allied landing would probably be on Biak, and a preliminary landing was made on 17 May at Wakde on the way to Biak. There a smaller airfield was available, which could be used as an advanced base until the Biak strips were ready. While initial Allied G2 estimates of Japanese troops were approximately 5,000, an intercepted message at the end of April gave the ration strength as 10,800. However, this figure was thought to be projected strength, rather than current strength.Bleakley 1991, p. 150
Battle The invasion force assembled largely in the Humboldt Bay area near Hollandia, and after only limited rehearsals departed late on 25 May.Smith 1996, pp. 289–290 After a 45-minute pre-landing naval bombardment,Smith 1996, p. 287 the 41st Infantry Division of the United States Army landed on Biak on 27 May 1944, initially with the 162nd Infantry Regiment, and soon followed by the remainder of the division, including the 163rd and 186th Infantry Regiments. By 5:15 in the afternoon 12,000 troops had landed, with 12 M4 Sherman tanks, 29 field guns, 500 vehicles, and 3,000 tons of supplies, including 600 tons aboard vehicles.Smith 1996, pp. 287–298 Several minor Japanese air attacks took place against the US lodgment on the first day; initially these were not pressed too heavily, but in the afternoon two waves of aircraft attacked the LSTs around the western jetty. Several bombs were dropped but failed to explode. Three aircraft were destroyed, and one was badly damaged by anti-aircraft fire from the US ships and guns that had been brought ashore.Morison 2001, p. 113
After a brief attack on the beachhead by a group of Japanese light tanks, which was defeated by a group of M4 Shermans in the first tank against tank engagement of the Pacific War,Smith 1996, p. 310 the US regiment moved inland quietly confident and expecting little opposition. This perception changed completely when they reached the airfield. From low-lying terrain and surrounding ridges came a storm of heavy weapons fire that pinned the US troops down. It was not until dark that amphibious tractors could be brought up to extricate them from the trap. The next day they reached the end of Mokmer airstrip. (Sorido airstrip was the objective.) The Japanese held firm, delaying its capture.Bleakley 1991, p. 153 With the slow progress the US command pulled their forces back, relieved Major General Horace Fuller of command of the 41st Division and reinforced the division with the 34th Regimental Combat Team (34th RCT) of the 24th Infantry Division.Smith 1996, p. 343
On 5 June the 186th Infantry, with the 2nd Battalion of the 162nd Infantry attached, moved to the eastern bases of the ridges dominating Mokmer strip. A coordinated attack was launched on 7 June which resulted in the capture of Mokmer strip and the establishment of a beachhead south of the strip; however, Japanese resistance continued in the area, particularly in the caves overlooking the area, and prevented engineers from improving the airfield. The engineers recommenced their efforts on 13 June but were once again disrupted by the Japanese.Morison 2001, p. 132 General Robert L. Eichelberger assumed command of the Hurricane Task Force on 15 June, tasked with renewing the attack. The new attack plan was to drive the Japanese from all terrain upon which they could fire on Mokmer Drome. First the West Caves, the Japanese encampment area, was cleared by the 186th Infantry Regiment, who then moved up on the ridges. The 34th RCT, supported by the 167th Field Artillery Battalion, occupied Borokoe and Sorido Dromes almost without opposition.Smith 1996, pp. 369–380
The US forces had been delayed 10 days. With the delay, the Fifth Air Force Command looked for alternative sites from which they could operate. They arranged the capture of the nearby island of Owi on 2 June and built Owi Airfield comprising two 7,000-ft airstrips there. An advanced echelon was stationed there composed of a bombardment group, two fighter groups, a P-61 Black Widow night fighter group, and a garrison of 15,000 troops.Bleakley 1991, p. 155
Control of Biak nearly became a critical turning point battle in the campaign for the Pacific. The Japanese had been seeking to engage the Americans in a decisive battle, the Kantai Kessen, that would enable them to win the war. Biak was not far from major Japanese fleet units and there were a number of land airfields nearby that could support the land-based aircraft the Japanese were hoping to concentrate to defeat the US fleet. The Imperial Navy's Chief of Staff, Admiral Ryūnosuke Kusaka, believed Biak represented the Allies' main effort, and a counterattack at Biak could provoke the US Navy into engaging in a major action.Willmott 1984, p. 186 In response to the landing at Biak by US forces, the Japanese launched an operation to reinforce the area. Initially, for air support, the Japanese 23rd Air Flotilla initially only had 18 aircraft but was later reinforced with up to 166 aircraft, which were moved to Sorong, in Dutch New Guinea, arriving from Japan and the Marianas.Vego 2016, p. 227
The Imperial Japanese Navy also began planning to reinforce the island under Operation KON (渾作戦) . Planning for this operation began on 29 May. A total of 2,500 troops from the 2nd Amphibious Brigade were assigned for transport from Mindanao; they were to be escorted by a force under Rear Admiral Naomasa Sakonju, consisting of the battleship Fuso, the heavy cruisers Aoba, Myoko and Haguro, the light cruiser Kinu, and eight destroyers (five as part of the screen and three as part of the transport element). They were scheduled to reach Biak on 3 June; other forces were to be transported from Manokwari by barge.Morison 2001, p. 118
Admiral Soemu Toyoda, commander of the Japanese Combined Fleet, initially attempted to reinforce Biak to hold the airstrips, but his first reinforcement sent 1 June was turned back when a Japanese scout plane mistakenly reported a US aircraft carrier in the vicinity. A second relief effort on 8 June was intercepted and driven off by American and Australian naval forces. A third attempt, with the support of the super-battleships and , was scheduled for 13 June, but the American invasion of the Marianas forced the Imperial Navy to redirect their forces to the Marianas for a major confrontation in the Philippine Sea.Bleakley 1991, p. 154