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Biak

Digital relief map of Biak

Photograph of Mokmer airfield under bombardment

U.S. Army. Via ibiblio.org

Biak is the largest of the Schouten Islands, located in Geelvink Bay (Cenderawasih Bay) on the north coast of western New Guinea. Biak is about 45 miles (72 km) long and 25 miles (40 km) wide. The somewhat smaller island of Soepiori is located to the northwest, across a very narrow strait, and the Padaido Islands are scattered to the southeast. Biak itself is mostly a low plateau covered with jungle and reaching to 2428' (740 meters) to the northwest, but there is a coastal plain on the south with considerable flat ground suitable for airfields. There are no natural anchorages and the island is almost completely surrounded by a formidable reef. The administrative center was Bosnik, on the southeast coast, where the reef was a bit narrower and was crossed by two stone jetties. The indigenous population numbered about 25,000 in 1944.

There is a 200 foot (60 m) escarpment extending from east of Bosnik (136.236E 1.170S) to Mokmer village (136.136E 1.200S). This escarpment is about 500 yards (460 m) inland along most of its length, but comes close to the shore at Parai (136.155E 1.193S), leaving just enough room for a road. Behind the escarpment, the terrain drops to a plateau, about 100 feet (30 m) in elevation, which is generally flat but locally rough ground. The plateau was covered with scrub, transitioning to dense forest two or three miles (three to five km) inland. West of Mokmer village, the escarpment turns north and runs inland for about a mile and a half (two and a half kilometers) before turning west again and running to the southwest corner of the island. This creates a relatively broad coastal plain suitable for airfield construction. The escarpment is coral with numerous caves, some of which are quite large.

The Japanese occupied the island in the spring of 1942 and built an airfield on the coastal plain west of Mokmer (136.107E 1.189S) capable of operating bomber aircraft. 222 Regiment from 36 Division was brought in from China in late 1943 to garrison the island. By 1944 there were additional airstrips at Bosnik (136.080E 1.173S) and Sorido (136.061E 1.162S), and the whole airfield complex was protected by substantial concentrations of dual-purpose and antiaircraft guns. 19 Naval Guard Force was sent to the island in May 1944, just in time for the Battle of Biak.

The Battle of Biak

Following their invasion of Hollandia, the Americans discovered that it would take many months to make the airfields at Lake Sentani capable of supporting heavy bombers. Aerial reconnaissance revealed that Biak was the nearest promising location for such airfields along MacArthur's line of advance. Aircraft based here would be well situated to support Nimitz' landings on the Marianas and Palau. MacArthur therefore ordered 6 Army (Krueger) to execute an expedited assault schedule on 10 May 1944, with a preliminary assault at Wakde on 17 May to secure airfields for local air cover and an assault on Biak ten days later. The landings were to be carried out by Hurricane Force, built around 41 Division  (Fuller), minus one regimental combat team, with the naval forces commanded by Fechteler. 41 Division was reinforced with most of a tank company, additional antiaircraft and artillery, and three airfield engineer battalions.

The landings were planned in considerable haste, both to ensure the airfields would be in operation by the time of the Marianas invasion on 15 June and to ensure that momentum would not be lost for MacArthur's drive on the Philippines. Fuller was under considerable pressure to ensure that the airfields would be secured by 10 June.

Aerial reconnaissance showed that the reef offshore of Mokmer was unfavorable for the passage of landing craft, while the coast further east towards Parai was heavily fortified and the terrain between Parai and Bosnik was mostly mangrove swamp that afforded little room for maneuver. The decision was therefore made to land at Bosnik. However, this meant that the landing force would have to advance a considerable distance along the coast road at the foot of the escarpment to reach the airfields at Mokmer. Because conventional landing craft would not be able to cross the reef even at Bosnik, the landing plan called for six LSTs to launch 63 LVTs and 25 DUKWs to bring the first four waves ashore. Subsequent echelons would land at the jetties from 15 LCIs. Engineers and their equipment would be landed on the reef early in the invasion from eight LCTs to prepare beaching ramps for LSTs carrying tanks.

Digital relief map of battle area on Biak

The LVTs were manned by 542 Engineer Boat and Shore Regiment while the DUKWs were manned by African-American troops. The DUKW drivers were hastily trained to operate out of LSTs at the rehearsal held at Hollandia on 23 May 1944. They performed well in the actual landing in spite of considerable confusion.

Preliminary air strikes were carried out by both 5 and 13 Air Forces from Nadzab and the Admiralties on 17 May 1944. A total of 99 B-24 Liberators participated in these raids. Strikes continued almost daily until the landing date, and were joined the last three days by A-20s based on Hollandia. Other strikes were directed at Japanese airfields in the Vogelkop Peninsula west of Biak by Liberators from Darwin.

Landings. The landing force embarked most of 41 Division on 25 May 1944 and sailed that evening. It was joined next morning by the cruiser forces under Crutchley and Berkey. Fighter cover was provided by 5 Air Force from Wakde. Fechteler did not expect to achieve surprise, but the Japanese reconnaissance aircraft that detected his force the next day was not itself detected, and Fechteler incorrectly believed he had achieved surprise after all.

The Japanese had expected an assault on Biak following the invasion of Hollandia, but not so quickly. Biak was originally planned to be an important link in the Japanese perimeter, but the Japanese high command vacillated badly over whether to attempt to hold Biak or let it be sacrificed to buy time while a stronger perimeter was established further west. On 9 May 1944 Imperial General Headquarters announced that the perimeter was to be pulled back to Sorong, then changed its mind two days after the Allied landings and ordered a powerful naval response.

The Biak garrison consisted of 11,000 troops of whom 4000 were combat trained. These were mostly from 222 Regiment under Colonel Kuzume Naoyuki and included a company of light tanks. The remaining troops included artillery, engineers, and 28 Special Base Force with about 1500 sailors. Kuzume expected the landings to take place near Mokmer and concentrated his forces accordingly. The invasion of Wakde on 17 May prompted Kuzume to end work on the airfields and begin extensive fortification work. Emphasis was put on the high ground north and northwest of Mokmer airfield with the intent to deny the Allies the use of the airfield for as long as possible. Fortifications included four 4.7" dual-purpose guns and a 6" coastal defense gun close to the beach. Other artillery, mortars, and automatic weapons were deployed on the escarpment behind Mokmer, with the strongest position in a set of limestone caves 1200 yards (1100 m) north of Mokmer airstrip. The Allies later discovered that these "West Caves" were centered around three sumps, the largest of which was 80' (25m) deep and 100' (30 m) across. West Caves had room for a thousand men. Another strong point was located in a smaller cave system ("East Caves") directly north of Mokmer village, east of the airstrip, while a third strong point with pillboxes was located just west of Parai ("Ibdi Pocket"). The latter two strong points were serendipitously located in ideal positions to ambush the American advance along the coast.

Elements of 41 Division (Fuller) began landing at 0629 on 27 May 1944.  Opposition at Bosnik was light except for a troublesome 4.7" gun situated in the Mokmer strong point that damaged a destroyer and was not permanently silenced for several days.  However, the weather was dead calm, and the preliminary bombardment by ships and aircraft of 13 Air Force soon obscured the landing area with smoke and dust. Some 400 rounds of 8" (203mm), 1000 rounds of 6" (152mm), 3740 rounds of 5" (127mm) and 1000 rounds of 4.7" (119mm) ammunition was allocated for the area around the airfields and another 4900 rounds of 5" and 4.7" ammunition were allocated for the landing beaches at Bosnik. The initial five waves were caught in a 2 to 3 knot current, and landed about two miles (3 km) west of the planned landing beach before destroyer Kalk located the stone jetties on radar and discovered the mistake. The first wave found itself in a mangrove swamp but quickly regrouped, and the sixth and subsequent waves were directed to the correct beach. The jetties were found to be in good condition and the remainder of the landing went according to plan. By nightfall, about 12,000 troops, 12 tanks, 18 artillery pieces, 500 vehicles, and 1400 tons of supplies were ashore. 186 Regiment was able to advance from the swamp to the coastal road and 162 Regiment was ashore on the correct beaches.

The initial confusion during the landings led to the first controversy of the battle. The commander of 186 Regiment, finding himself on the coast well west of Bosnik, recommended that his regiment swap missions with 162 Regiment, so that 162 Regiment would secure Bosnik while 186 Regiment raced west towards the airfield. Fuller rejected the recommendation, feeling that this would compound the confusion.186 Regiment moved east to secure the beachhead while 162 Regiment drove west through their lines and began a rapid advance along the coastal road towards Mokmer, reaching Parai before digging in for the night.

Japanese aircraft put in a modest appearance during the first day. Four fighters appeared over the airstrips at 1100 but quickly retreated. Two fighters and four bombers appeared late in the afternoon and succeeded in hitting an LST with bombs that proved to be duds. Three of the bombers were shot down, but one succeeded in crashing into SC-699, which was set on fire and suffered two dead and eight wounded before the fires were put out and the submarine chaser salvaged

Opposition was so light the first day that Barbey speculated that the Japanese had evacuated the island. This was far from the case. Although the Japanese had spotted the invasion convoy, they were caught out of position and relatively unprepared for the attack. 2/222 Regiment was in place in the East Caves, but the other units were mostly scattered across the inland plateau. The command situation was further confused by the presence of Lieutenant General Numata Takazo, chief of staff of 2 Area Army, and Rear Admiral Senda Sadatoshi, who were both on an inspection trip from the area headquarters at Manokwari. Numata apparently directed Kuzume to abandon his plans for a defense in depth and carry out counterattacks in accordance with the traditional Japanese emphasis on the offensive. Numata left the island on 15 June, after which Kuzume reverted to his strategy of defense in depth. Senda remained on the island and shared the fate of the garrison, placing himself under Kuzume's tactical command.

Counterattack at Mokmer. MacArthur had discounted accurate intelligence showing 11,000 Japanese troops and light tanks on the island, believing there were not more than 4400 defenders. The intelligence was confirmed when 162 Regiment began to close on the airfield on the morning of 28 May 1944. The forward elements had gotten within 200 yards of Mokmer airfield when the Japanese defenders suddenly opened fire from the East Caves and Ibai Pocket, ambushing the American column. Elements of 2/222 Regiment attacked from the west and north and soon had 3/162 Regiment trapped in a perimeter 200 yards deep and 500 yards long. 1/222 Regiment attempted to outflank the Japanese by advancing along the ridge from Parai but were stopped by fire from East Caves. A platoon of Sherman tanks helped drive back an attack supported by Japanese tanks, but 1 and 2 Battalions were unable to break through to relieve 3 Battalion. Supplies had to be brought in, and casualties evacuated, by landing craft. The naval support officer with 162 Regiment was killed around noon, which greatly hindered cooperation with destroyers offshore. At 1600 Fuller ordered 3 Battalion to pull back behind 2 Battalion's lines. Four of the Shermans covered the withdrawal, which was completed by 1900.

Destroyer gunfire was unsuccessful in driving the Japanese back during the night, and the Japanese moved 1 Battalion, 222 Regiment to West Caves from its bivouacs to the north and prepared to throw all of 2 and 3 Battalions against the Americans the next morning. The counterattack was supported by light tanks, but these were completely outclassed by the Shermans, which knocked out seven of the Japanese tanks while the Japanese infantry took heavy casualties. However, by noon the Japanese had cut the coastal road at Parai and it was clear that 162 Regiment was in an untenable position. The American tanks were able to cover the evacuation of 2 Battalion in LVTs while the remainder of 162 Regiment cleared the roadblock at Parai and moved back to Ibdi (136.190E 1.178S).

Seizing Mokmer Airfield. Fuller called for reinforcements for an attack to clear the escarpment. He was given two battalions of 163 Regiment from Wakde, and 503 Parachute Regiment began moving to Hollandia in case it was also need. During the two days it took to bring up the two infantry battalions in LCIs, 162 Regiment regrouped and rested, except for patrol activity that identified the Ibdi Pocket and found two trails across the escarpment. The Japanese also regrouped. Although some 800 men of 3/222 Regiment remained largely idle in the Ibdi Pocket, Kuzume moved naval troops and a mortar company in the East Caves, reorganized most of 2/222 Regiment around West Caves, and pulled 1/222 Regiment back to a position well north of Bosnik.

The American attack resumed on 1 June 1944, with 186 Regiment advancing west along the inland plateau while 162 Regiment resumed its drive along the coast. 1/222 Regiment attempted a counterattack that night against the northern flank of 186 Regiment, but this was beaten off with heavy losses, with the Japanese battalion commander among the dead. The Japanese survivors continued withdrawing before 186 Regiment and would ultimately end up at West Caves. Thereafter 186 Regiment was more seriously hindered by terrain and lack of fresh water supplies than with the Japanese. (At one point, a tropical downpour was all that prevented the advance from bogging down for lack of water.) Meanwhile 162 Regiment had recognized that the Ibdi Pocket was a major strong point. After a pause on 3 and 4 June to await the outcome of Operation KON (see below), the advance resumed.

By 6 June, 186 Regiment was preparing to advance along the terrace north of Mokmer airfield to clear any Japanese positions overlooking the airfield. However, Fuller, who was under pressure from Krueger to get at least one airfield operational as soon as possible, ordered the regiment to prepare to move south immediately and seize the airfield and a beachhead around it. Because of inadequate patrolling by one of his battalions, the regimental commander failed to recognize that he was in a good position to outflank strong Japanese positions on the ridge north of Mokmer airfield. Instead, 186 Regiment headed directly to the airfield, under cover of an intense artillery barrage, and after occupying the field found itself under fire from formidable Japanese fortifications on the ridge to the north. There followed an artillery duel in which some 40% of the Japanese guns were silenced, but the remainder kept the airfield from being put into operation. Furthermore, 186 Regiment had had to abandon its tenuous supply line back across the ridge and the inland plateau to Bosnik, and the Japanese at Ibdi Pocket and the Parai defile had kept 162 Regiment from clearing the coastal road. Additional supplies had to be run in by landing craft under Japanese fire, which was possible only after infantry with tank support had cleared the Japanese fortifications along the beach south of Mokmer airfield.

The battle for Biak now became a battle of attrition. Kuzume had 1 and 2 Battalions, 222 Regiment; 19 Naval Guard Force; and most of his Army service troops and heavy weapons at West Caves and the ridge north of Mokmer, some naval troops and mortars at East Caves, and 3/222 Regiment in the Ibdi Pocket. Fuller ordered most of 3/162 Regiment moved by landing craft to the Parai jetty, from which it was to move east and, presumably, take the Japanese at the Parai defile from the rear. Instead, the battalion was hit by fire from East Caves and called for reinforcements of artillery and tanks. Frustrated with the Japanese resistance at Ibdi, Fuller decided to leave a single company to contain the Ibdi Pocket while 162 Regiment cleared the Parai defile, opened the coastal road, and moved west to join 186 Regiment at Mokmer airfield. The Ibdi Pocket would be left for 163 Regiment to reduce when it arrived.

Photograph of entrance to West Caves

U.S. Army. Via ibiblio.org

Clearing the West Caves. On 11 June Fuller launched a major attack by both 162 and 186 Regiments to the west from Mokmer airfield. Each regiment put two battalions into the attack and held the third back at Mokmer airfield as reserves. Meanwhile 3/163 Regiment patrolled along the ridge to the north and northeast. Three of the assault battalions advanced against very light opposition, but the fourth and northernmost battalion, 3/162 Regiment, ran into stiff opposition along the terrace almost at once. The battalion had stumbled onto West Caves, and liberated Javanese laborers confirmed the presence of the Japanese stronghold. Company L, 163 Regiment, had meanwhile established an observation post on Hill 320, directly north of West Caves, and the observation post reported large concentrations of Japanese artillery around West Caves. Concerned by the resistance his men were facing, Fuller requested (and was given) the use of 34 Regiment.

On 12 June engineers began work on Mokmer airfield, repairing 2300 feet of runway by the evening of 13 June in spite of harassing mortar and artillery fire. Meanwhile, because of the delay in taking the airfields, Army engineers explored the Paidado Islands and determined that Owi had excellent terrain for an airfield. Construction on Owi began on 9 June, but the field would not be not ready for fighters until 17 June.

On 14 June the two reserve battalions were ordered to attempt to outflank the Japanese positions to the north. One of the battalions drove almost to the periphery of the West Caves, and Kuzume responded with a counterattack on the morning of 15 June. This was thrown back by bazooka teams and artillery but spoiled the American's own plans for an attack that day.

By now MacArthur's patience had run out, and on 15 June Fuller was relieved by Eichelberger. Krueger's instructions were for Eichelberger to take command of Hurricane Force and leave Fuller in command of 41 Division. However, Fuller felt he had lost the confidence of MacArthur and Krueger and requested relief from his division command and reassignment outside Southwest Pacific Area. Doe took command of 41 Division.  Eichelberger renewed the attack on 16 June, and by the evening of 17 June two battalions were on high ground overlooking West Caves. After a pause to regroup, the bulk of both 162 and 186 Regiments were thrown against West Caves, which were isolated by nightfall on 19 June. However, the strong point was not reduced until 27 June, after the Americans had employed drums of gasoline, hand grenades, direct fire from tanks, and demolition charges against the stubbornly entrenched Japanese. A large force of Japanese attempted unsuccessfully to break out on the night of 21-22 June, while the fate of Colonel Kuzume himself is uncertain; some reports claimed he committed ceremonial suicide immediately after the breakout attempt, while others claimed he was killed in action or committed suicide some days later. However, as the Americans closed the ring on West Caves, their engineers were finally able to work unhindered on Mokmer airfield, and it began operating fighters on 22 June.

Meanwhile Borokoe and Sorido airfields were occupied by 34 Regiment, which had arrived on Biak on 18 June. 34 Regiment participated only briefly in the battle, going back into 6 Army reserve on 30 June, by which time the entire area north of the airfields had been mopped up. There was brief fierce resistance around a cul-de-sac northwest of Hill 320 dubbed The Teardrop, but this was cleared by 25 June.

Photograph of entrance to East Caves

U.S. Army. Via ibiblio.org

East Cave and the Ibdi Pocket. Meanwhile the Americans had renewed the assault on the strong points at East Caves and the Ibdi Pocket. East Caves was occupied by about 1000 troops, mostly engineers and service troops with a very thin leavening of mortar crews and riflemen from 222 Regiment. The Japanese here had fired intermittently on the airfields starting on 7 June, and American patrols had identified some of the Japanese positions, but the Americans considered it more urgent to reduce the West Caves and had left the East Caves to be neutralized by artillery and mortars. From 7 to 10 June, more than 1000 shells had been fired on the positions. By 13 June the American artillery and patrols had suppressed fire from the East Caves sufficiently that the coastal road was finally open to truck traffic. Harassing fire continued until 27 June, and included a number of skip-bombing sorties by B-25s from Mokmer airfield on 23 or 24 June.

Fire from the caves on 27 June was sufficiently troublesome to American engineers constructing a jetty near Mokmer village that mortars and artillery were again brought in to suppress the Japanese guns. Some 1600 rounds were fired into the caves, and the Americans increased their patrols into the area. On 3 July, engineers and infantry from Mokmer airfield moved into the East Caves under cover of tank fire and began blasting shut the caves. The Americans broke into the main positions on 5 July to find that most of the troops had already slipped away. However, a few survivors remained in the area until 20 July, when the Americans responded to an ambush of Australian souvenir seekers by sending in tanks and infantry to thoroughly mop up the position.

The attack on the Ibdi Pocket had begun on 1 June but had made only slow progress.  However, the Parai Defile was finally cleared on 12 June, and the newly arrived 163 Regiment took over responsibility for clearing the rest of the Ibdi Pocket while 162 Regiment moved west to join 186 Regiment at Mokmer airfield. Between 12 June and 20 June, 163 Regiment carefully scouted the escarpment, then launched a major attack. This met stubborn resistance, and by 28 June the exhausted infantry was back to patrolling for targets for artillery and air bombardment. From 21 June to 10 July, at least 40,000 artillery and mortar shells were fired on targets in the Pocket, and on 10 July a patrol reported that the Japanese defenders were considerably reduced and that the heavy bombardment had stripped much of the cover from the Japanese positions. The assault was renewed the next day by infantry with bazookas and flamethrowers and heavy tank, artillery, and air support, and on 22 July all organized resistance had ceased. Mopping up continued until 25 July.

On 28 June 2 Army had ordered the remains of Biak Garrison to withdraw into the wilds of the island and prepare for guerrilla warfare. Some 4000 Japanese troops were at large on the island, most of whom began making their way to Wardo Bay (135.824E 1.031S) on the west coast, and the Americans turned to mopping up these troops before they could reorganize.  Patrols were sent far north of the escarpment, and on  2 August, 2/162 Regiment landed at Korim Bay (136.042E 0.912S), on the northeast coast of Biak, and moved south to make contact with 3/163 on 15 August. 1/186 Regiment landed at Wardo Bay on 17 August. By 20 August the island was considered secured.

The Americans suffered casualties of 474 dead or missing and 2428 wounded during the battle. An epidemic of scrub typhus contributed another 1000 casualties, while another 3500 troops were diagnosed with "fevers of undetermined origin." The Japanese lost about 4700 dead and another 220 prisoners.

Operation KON

The Japanese Navy high command reacted strongly to the Biak invasion, which threatened to disrupt plans for a decisive battle in the central Pacific (A-Go.) Ozawa's Mobile Fleet, the main striking power of the Japanese Navy, had already assembled at Tawi Tawi in anticipation of the battle. However, the Japanese Army had written off Biak, and the Navy had allocated only the 18 aircraft of 23 Air Flotilla (Ito) at Sorong to repel any attack on Biak.

The Navy began concentrating its land-based air power in western New Guinea on 28 May 1944, ordering an additional 70 fighters and 20 bombers from Japan and the Marianas to join 23 Air Flotilla. Another 20 bombers, 8 reconnaissance aircraft, and 48 fighters were redeployed from the Carolines on 31 May. By then orders had been hastily prepared for Operation KON to relieve Biak.

The Japanese assembled a strong force around three heavy cruisers, a light cruiser, eight destroyers, two minesweepers, and battleship Fuso to transport the 2500 men of the Army's 2 Amphibious Brigade from Zamboanga to Biak. Since only one transport (a Japanese LST) was available, most the troops were embarked on the warships. The troops embarked on 31 May and expected to debark at Biak on 3 June. Air cover was to be provided by and additional troops were to be brought in on barges from Manokwari by Southwest Area Fleet.

KON kicked off with a large Japanese air raid against a group of 8 LSTs unloading at Bosnik on the afternoon of 2 June 1944. The Japanese mustered 54 aircraft for the raid and encountered no Allied fighter opposition due to inclement weather over Wakde and Hollandia. However, antiaircraft fire from ship and shore was extremely heavy and the Japanese lost 12 aircraft while inflicting only slight damage on one LST.

That night the Japanese surface force, divided into three groups, set out for Biak. By noon the next day they were under observation by American Liberators. The loss of surprise, combined with mistaken intelligence reporting an American carrier off Biak, prompted Toyoda to suspend the operation. Fuso, two heavy cruisers, and two destroyers returned to Davao, only to have destroyer Kazagumo sunk by submarine Hake at the harbor approaches. The remaining ships proceeded to Sorong, disembarking their troops on 4 June 1944. Unknown to the Japanese, the American reconnaissance was directed by Ultra decrypts.

The Japanese staged a second raid against Biak on 3 June 1944. Three destroyers, eight LCTs, and four LCIs off Bosnik were attacked by 32 Zeros and 19 bombers. The attackers were detected on radar at 1100 and the ships were able to avoid serious damage by violent maneuvers. Allied fighters arrived at 1125 (after being delayed by weather) and drove off the remaining Japanese aircraft. The Japanese lost 11 aircraft but were promptly reinforced by another 70 aircraft from the Marianas.

By then Kinkaid had concluded that the Japanese meant to make a major naval effort to relieve Biak. Crutchley was ordered to refuel, then take Berkey's cruiser group under his command, and the combined cruiser force had reached a point 25 miles north of eastern Biak by 1900 on 4 June 1944. All other Allied forces were ordered to clear the area. The Japanese had sighted the Allied surface force, and they launched a raid that arrived at 1740. One light cruiser was slightly damaged.

Crutchley had intelligence that the Japanese meant to land on the west coast of Biak, and he chose to sweep the south and west coasts of the island, barely avoiding a friendly fire incident when he passed the American shore batteries at Bosnik. No Japanese surface force was encountered and Crutchley retraced his course back to his patrol station northeast of Biak. Here he was attacked by four Japanese night torpedo bombers, which inflicted no damage. However, the Japanese launched a second night raid by two bombers against Wakde that caught over a hundred Allied aircraft parked closely together on the runway. This raid inflicted very heavy damage and put the airfield out of action for several days. So embarrassing was the episode that the official U.S. Air Force history barely mentions the raid and quotes no casualties, but at least two-thirds of the aircraft on the island were put out of action.

The Japanese made a second attempt to run in reinforcements on three landing barges towed by six destroyers. Two cruisers remained off the western tip of New Guinea to await developments while 23 Air Flotilla was directed to provide fighter cover. The reinforcement flotilla embarked 600 troops at Sorong and sailed for Biak at midnight on 7 June. However, it was spotted by Allied aircraft at 1245 the next day. In a low-level strafing attack by 10 B-25s, the Allied aircraft sank destroyer Harusame and slightly damaged three others.  Sakonju pressed on with the five surviving destroyers, but at 1900 he received a report that an Allied task force was racing to intercept him. Again, Ultra decrypts had warned the Allies.

Crutchley had been delayed by maneuvers to evade Japanese snoopers, and his force did not arrive off the west coast of Biak until 2200 on 8 June 1944. Shortly thereafter a PB4Y spotted Sakonju's force 60 miles (100 km) to the north-northwest. Crutchley ordered a turn to the north to cross the Japanese "T", but one of his destroyer divisions, DesDiv 42, ignored the order and raced towards the Japanese. The two forces sighted each other on radar at about 2320, and Sakonju promptly launched torpedoes and fled. The commander of DesDiv 42 radioed a warning to Crutchley, which was confirmed when one of the "fish" passed close astern of cruiser Boise. By then Crutchley's remaining destroyers were also in hot pursuit of the Japanese. Though no torpedo hits were inflicted on the Allies, they were unable to catch the fleeing Japanese force, although the two forces came close enough to exchange gunfire and for the Japanese to launch another wave of torpedoes. The Allies finally gave up the pursuit at 0230, lest they be mistaken for Japanese ships by their own aircraft when daylight came.

The Japanese had cast off the three landing barges early in the action. They were fired on by the American destroyers in passing, but the barges apparently made it to shore and landed a few reinforcements on Biak. However, the majority of the 600 troops in the reinforcement group were taken back to Sorong aboard the Japanese destroyers.

Finally, by 11 June 1944, the Japanese assembled an armada off Halmahera that included both Yamato and Musashi. This powerful force was scheduled to arrive at Biak on 15 June, deliver a heavy bombardment, and land its troops, but this operation was called off on 12 June when heavy air strikes against the Marianas indicated that Spruance would soon begin his landings there. It has been suggested that the Japanese would have done better to stay with their Kon plan, which would probably have inflicted a serious defeat on the weak American naval forces off Biak, rather than send the super battleships north to a battle to which they contributed little. As it was, 23 Air Flotilla got in a final shot before being withdrawn to Palau, inflicting serious damage on destroyer Kalk in a raid by four aircraft on the morning of 12 June.

The failure of Kon was costly for the Japanese. In addition to their naval losses, the diversion of so much land-based air power to western New Guinea seriously disrupted Japanese plans for A-Go and contributed to the debacle of the Battle of the Philippine Sea. Most of the pilots diverted to provide air cover for Kon promptly came down with malaria or other tropical diseases and were unable to participate in either Kon or A-Go as a result.

The Japanese subsequently managed to slip perhaps 1100 troops in barges from Noemfoor through the Allied blockade to Biak. These were mostly drawn from 219, 221, and 222 Regiments and most landed at Korim Bay, from which they made their way to the West Caves strong point.

Aftermath

During the battle, a Japanese naval radio unit ran into an American patrol and lost several code books. This prompted the Japanese to make emergency changes in their radio procedures, which slowed down their communications just as the Battle of the Philippine Sea was getting under way.

Engineers had begun improving the facilities at Bosnik on the first day of the landing. On 30 May 1944 a naval demolition team blasted a 5 foot (1.5 m) deep channel through the reef to allow LCMs and LCVPs to land directly on the beach. By 17 June an airstrip had been completed on Owi and two squadrons of P-38s from 8 Fighter Group arrived on 21 June. On 22 June the first fighters were operating from Mokmer airstrip. By 12 July the Owi airfield had a 7000' (2130 m) runway and a second was completed on 20 August. The airfield eventually had 20,000' (6100 m) of taxiways and 130 hardstands.

Mokmer was first put in operation on 22 June and by 1 August the runway was extended to 7000' (2130 m), with 27,000' (8230 m) of taxiways and 122 hardstands. A 4000' (1200m) runway was completed for transport aircraft at Borokoe by 1 August and this was extended to 5500' (1680 m) by 20 August. Sorido was on less suitable ground, and while a 4000' (1200 m) runway was briefly in use, the airfield was quickly abandoned. Unfortunately, none of these airfields was ready in time to give significant support to the Marianas invasion.

The south coast of Biak had eight LST ramps, two floading docks for Liberty ships, and five jetties by 20 August. The area thus became a major base for the Allies in the Southwest Pacific.

Allied order of battle, 27 May 1944

Southwest Pacific Area (MacArthur)     

 
7 Fleet (Kinkaid)


 
Task Force 77 (Barbey)



 
DD Swenson




Task Group 77.2 Attack Group (Fechteler)     
41 Division (Fuller) less 163 Regimental Combat Team
603 Tank Company (12 M4 Sherman tanks)
Two antiaircraft battalions
Two artillery battalions
Three aviation engineer battalions




DD Reid





Transports






APD Herbert





APD Kilty





APD Ward





APD Crosby





APD Schley





15 LCI
6 LST





Screen






DD Hobby





DD Nicholson





DD Wilkes





DD Grayson





DD Gillespie





DD Kalk





DD Stockton





DD Roe






DD Welles





DD Sampson






DD Warrington





DD Balch





Special Service Vessels






5 SC
2 LCI





Destroyer Squadron 2






DD Morris






DD Anderson





DD Hughes





DD Mustin





DD Russell





DD Ellet






DD Lansdowne






DD Lardner


Task Force 74 Covering Group "A" (Crutchley)




CA Australia




CA Shropshire




DD Warramunga




DD Arunta



DD Ammen



DD Mullany


Task Force 75 Covering Force "B" (Berkey)




CL Phoenix




CL Nashville



CL Boise



Destroyer Squadron 24




 
DD Hutchins




DD Bache




DD Daly




DD Abner Read





DD Bush


Task Force 73 Aircraft Seventh Fleet



Task Group 73.1 Seeadler Harbor Group




AV Tangier




AVP Heron




AVP San Pablo




VP-33 13 PBY-5




VP-52 13 PBY-5




VB-106 11 PB4Y-1 Liberator



Task Group 73.2 Langemak Bay Group




AVP Half Moon




VP-34 10 PBY-5

Japanese order of battle, 27 May 1944

2 Area Army (Anami)     

 
Biak Detachment
11,400 men, of whom about 4000 were combat trained.

 
222 Regiment
3400 men


 
Tank company
10 Type 95 light tanks


17 Airfield Construction Unit
107 Airfield Construction Unit     
108 Airfield Construction Unit
500 men each


28 Naval Special Base Force (Senda)     
1500 men



19 Naval Guard Unit
125 men. Only naval unit on island with combat training.

Photo Gallery


Map of south Biak coast

U.S. Army

Air raid on Mokmer airfield

U.S. Army

Detail map of coastal road

U.S. Army

African-American troops unload stores

U.S. Coast Guard

Oblique aerial shot of East Caves
U.S. Army
The Parai Defile
U.S. Army
Map of the attack north of Mokmer airfield
U.S. Army
West Caves
U.S. Army
East Caves
U.S. Army
Port facilities at Biak
U.S. Army

References

Morison (1953)
Prados (1995)

Rottman (2002)

Smith (1953; accessed 2013-6-22)

Spector (1985)

Taaffe (1998)


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