World War Two: Biak: West to Mokmer Drome (AP-13)

After spending a night disturbed only by a few Japanese mortar shells, the 162nd Infantry resumed its westward advance at approximately 0730 on 28 May. Just past the Parai Defile the seaward side of the main coastal ridge gives way to an inclined terrace about 500 yards wide and a mile and a half long. Slanting toward the shore, this terrace ends in the twenty-foot-high cliff located along or near the water line from Parai west beyond Mokmer village. The 162nd Infantry planned to send part of its 3rd Battalion along the terrace, inland, while the rest of the unit advanced along the coastal road, which runs from the Parai Defile partly beneath the cliff and partly along its crest. The 2nd Battalion was to move along the terrace to the right rear of the 3rd, while the 1st Battalion was to take up reserve positions at Parai. The advance was to be supported from the shore by the 146th Field Artillery and the 603rd Tank Company. Destroyers were to stand offshore to provide fire support on call.

An Initial Reverse: Prelude to Retreat

The 3rd Battalion, 162nd Infantry, proceeded through Mokmer village without opposition. Company L and some of Company M’s heavy machine guns then moved on to the terrace above Mokmer, leaving the rest of the battalion to continue toward the airdromes along the coastal road. By 0930 the main body of the battalion was at a road junction nearly 1,500 yards west of Mokmer. Slight resistance along the road from Mokmer had been easily brushed aside, but at the road junction enemy resistance stiffened sharply and machine gun and mortar fire pinned down Company K, which was leading the advance. As the 146th Field Artillery Battalion tried to silence this fire elements of Company K pushed westward to within 200 yards of Mokmer Drome. This was as close as any troops of the HURRICANE Task Force were to approach that airfield for over a week.

About 1000 hours, Japanese infantry, elements of the 2nd Battalion, 222nd Infantry, counterattacked from the west.[n13-3] The forward units of the 3rd Battalion, 162nd Infantry, withdrew 600 yards along the coastal road to the point at which the twenty-foot cliff left the shore line, but Japanese infantry attacks, which were supported by automatic weapons fire, continued. The enemy threw more troops into the battle (more of the 2nd Battalion, 222nd Infantry) from the East Caves area until the attackers were coming not only from the west but also from the northwest and north. The Japanese split the 3rd Battalion by driving a wedge along the cliff between the troops on the shore and those on the terrace. Companies L and M were cut off. The 2nd Battalion, attempting to get on the terrace to the north of the 3rd Battalion, was pinned down by Japanese fire from the East Caves and was unable to advance.

[n13-3 Identifications of enemy units in this and the following subsections are based on: Opns of Yuki Group, p. 4; MID WD, Military Reports, 24, p.14; 2nd Army Opns at Sarmi and Biak (Rev), pp.56-59, 62.]

By 1100 the 3rd Battalion was in sore straits. The main body was on the coast in an area about 200 yards deep and about 500 east to west. Behind the battalion, the shore line was a twenty-foot cliff. The entire area was covered with secondary growth thick enough to prevent good observation along the ground but open enough to allow the Japanese in their higher East Caves position to view every American movement. The Japanese had excellent cover and concealment in the thick vegetation, coral caves, and crevices of the East Caves area and, at the same time, were able to subject the 3rd Battalion to intense mortar, grenade, machine gun, and rifle fire. Because of poor observation and the defiladed enemy positions, the fire of neither the 146th Field Artillery Battalion nor the offshore destroyers was able to silence the enemy’s weapons. Most of Company L and the Company M detachment which was also on the coral terrace managed to find a covered route back to the rest of the 3rd Battalion on the shore, but one platoon, initially surrounded, had to fight its way eastward into the lines of the 2nd Battalion, north of Mokmer village. Company G, on the terrace north of the main road and between the 2nd and 3rd Battalions, was also cut off and withdrew to the 2nd Battalion only with difficulty, and after it had suffered many casualties from Japanese fire. The 1st Battalion was ordered to move north from Parai onto the main coastal ridge to outflank the enemy positions, but efforts to do so were halted by enemy fire from the East Caves. Two companies patrolled in the broken terrain along the main ridge but were unable to move westward.

During the afternoon the 3rd Battalion stood off two more concerted enemy counterattacks, one at 1200 and another shortly after 1400, and suffered more casualties from the enemy mortar and artillery fire. During the latter attack, the Japanese began moving some light tanks forward from the Mokmer Drome area. The 3rd Platoon, 603rd Tank Company, engaged these tanks at a range of 1,200 yards and, with the aid of fire from destroyers lying offshore, drove the enemy tanks back into defilade positions. Three tanks of the 603rd were damaged by Japanese artillery fire and three men of the same organization were wounded during the action.

Meanwhile, General Fuller had decided to reinforce the 3rd Battalion, 162nd Infantry. The 1st Platoon, 603rd Tank Company, moved west along the coastal road. At the same time small boats manned by the 542nd Engineer Boat and Shore Regiment were also sent forward with ammunition and medical supplies, both dangerously low. The small craft moved along the shore out of range of Japanese mortar and artillery fire until opposite the 3rd Battalion’s position and then shot inshore at full speed, one by one. Supplies were replenished and the worst casualties evacuated despite continued shelling of the 3rd Battalion’s position by the Japanese. The 1st and 2nd Battalions continued their efforts to clear the Japanese from the terrace behind the 3rd but met with little success.

By late afternoon the 3rd Battalion’s position was becoming untenable. Japanese mortar and artillery fire increased and enemy patrols cut the coastal road to the rear. Obviously, no further advance could be made until the enemy fire from the East Caves area could be stopped by ground attack from the north, by naval fire from the south, or by artillery fire from emplacements to the east. Thus far, artillery fire had had little apparent effect upon the volume of Japanese fire. Only one artillery battalion was in position to fire on the East Caves area and the effect of its fire was limited by the location of the Japanese emplacements, most of which were either in deep defilade or were in caves and crevices facing seaward. Offshore destroyers and rocket LCI’s were in the best position to fire on the Japanese emplacements. The best expedient would have been increased fire from these naval vessels, but such fire was now impossible to obtain.

The naval fire support officer with the 162nd Infantry had been killed at the 3rd Battalion’s position about noon. Direct ship-to-shore communications immediately broke down, and no replacement for the liaison officer was immediately available. Communications to the offshore destroyers and rocket LCI’s remained erratic and slow throughout the 28th and the next day—messages had to be passed back from the 3rd Battalion to regiment, then to HURRICANE Task Force headquarters, to naval attack force headquarters, and finally to the naval fire support groups and individual ships. It was impossible to concentrate sufficient support fire on the Japanese positions to neutralize the artillery, mortar, and machine gun fire still falling on the 162nd Infantry’s forward elements.

About 1600 General Fuller gave up plans for further attempts at reinforcement of the forward units and ordered Colonel Haney to withdraw his 3rd Battalion to the positions held the previous night. The withdrawal started slowly because communications difficulties still prevented concentration of supporting fires. However, at 1700 the regimental commander finally ordered the 3rd Battalion to start moving back along the coastal road. Tanks were to act as point, and rear guard and close-in artillery fire was substituted for a disengaging force. The battalion was to continue eastward until it had passed through the 2nd, which was setting up a new defensive position east of Mokmer village.

The men of the 3rd Battalion moved in small parties along the beach and main road, which was intermittently swept by Japanese mortar, machine gun, and rifle fire. Many troops were unable to use the main road, but had to drop down to the beach below the overhanging cliff. Four tanks brought up the rear and protected the north flank. Between 1830 and 1900 all elements of the 3rd Battalion reached safety beyond the 2nd Battalion’s lines and began digging in for the night east of the latter unit. Casualties for the day, almost all of them suffered by the 3rd Battalion, were 16 killed and 87 wounded.

The First Attack Ends in Retreat

Sometime between dawn on 28 May and first light on the 29th, the 1st Battalion, 222nd Infantry, and the headquarters of the Biak Detachment had moved overland to the West Caves from their previous positions north of the surveyed drome behind Bosnek. With the 1st Battalion in reserve, Colonel Kuzume could throw the entire 2nd and 3rd Battalions against the 162nd Infantry. For the American regiment the night of 28-29 May proved quiet in comparison with the action during the previous day, but the Japanese were ready to launch strong counterattacks against it on the morning of the 29th.

The first Japanese attack began at 0700 on the 29th and was directed against the 2nd Battalion, 162nd Infantry. This attack, which was carried out by men of the 2nd and 3rd Battalions, 222nd Infantry, was beaten off by mortar, machine gun, and rifle fire without loss to the American unit. About 0800, new waves of Japanese infantry, now supported by four tanks, appeared west and north of the 2nd Battalion, thus beginning the first tank battle of the war in the Southwest Pacific Area.

The 2nd Battalion, 162nd Infantry, with the 1st Platoon, 503rd Tank Company, in support, was astride the main coastal road 1,000 yards east of Mokmer. The battalion’s left flank was on the beach while its right was against the coastal cliff and less than forty yards inland. (The right had been drawn in from an initial position on the terrace above the cliff after the 0700 attacks.) Between the beach and the cliff was a coconut grove. The main coastal road crossed the rise of the cliff at a point about 475 yards west of the 2nd Battalion’s lines.

Shortly after 0800 the Japanese tanks, followed by an infantry column, advanced down the incline where the main road crossed the cliff and deployed in echelon left formation in the coconut grove. The Japanese vehicles were light tanks, Model 95 (1935), weighing about nine tons, carrying a crew of three men, and armed with one 37-mm. cannon and two 7.7-mm. machine guns. They were opposed by two General Sherman M4A1 medium tanks, the heaviest armament on which was the 75-mm. gun. Each Japanese tank was stopped by one round of 75-mm. armor-piercing ammunition, while the enemy infantry was literally mowed down by the machine guns and mortars of the 2nd Battalion, 162nd Infantry. Armor-piercing 75-mm. shells passed right through the Japanese light tanks, and the Sherman’s followed with a few rounds of 75-mm. high explosive, which tore holes in the Japanese vehicles and blew lose their turrets. During this action several hits scored on the Sherman’s by the Japanese 37-mm. guns caused no damage.

About thirty minutes after the first attack the Japanese sent in a second wave of three tanks, which used the same route of approach and the same formation in the coconut grove. These three were quickly destroyed by three Sherman’s. One enemy 37-mm. shell locked the 75-mm. gun of one Sherman in place, but the American tank backed part way into a shell hole to obtain elevation for its weapon and, despite the damage, managed to destroy one of the enemy tanks. The Japanese tanks having been stopped and the leading elements of the second infantry wave killed, the attack disintegrated and the enemy withdrew.

For an hour or so the Japanese were quiet, but late in the morning, under the cover of machine gun fire and mortar barrages, they began to circle north of the 2nd and 3rd Battalions, 162nd Infantry. New infantry attacks began about 1200. The enemy was unable to dislodge the 162nd Infantry, but his mortar fire caused many casualties within the regimental perimeter and the Japanese managed to cut the coast road east of a large T-jetty at Parai. Company B and the Cannon Company (which was not armed with its usual 105-mm. howitzers but acted as an additional rifle company throughout the Biak operation) counterattacked the Japanese road block behind close-in mortar support and succeeded in dislodging the enemy by fire and movement.

By noon it had become apparent that no attack launched against the airdromes would be successful until the Japanese could be cleared from the high ground overlooking the fields and the approaches thereto or until Japanese fire from the East Caves area and the ridge line east of that position could be neutralized. On 29 May it was impossible to neutralize these enemy installations because the infantry troops were so close to them as to prevent effective artillery fire and because communications from the ground to support aircraft and naval vessels were, at best, sporadic. In view of these facts, Colonel Haney instructed his staff to prepare plans for withdrawal to Ibdi and Mandom by amphibious craft or by march through the Parai Defile. He then returned to the HURRICANE Task Force command post near Mandom to explain the situation to the task force commander and to confer on possible lines of action. At 1200 Colonel Haney returned to the forward area with approval for a withdrawal.

Colonel Haney’s plan was to have his 1st Battalion cover the withdrawal from positions at Parai, while the other two battalions and attached units moved both overland and by water back to Ibdi. One platoon of Company D, 641st Tank Destroyer Battalion (4.2-inch mortars), was to remain in place to maintain supporting fire during the withdrawal. The 542nd Engineer Boat and Shore Regiment was to supply small craft and amphibian vehicles for the overwater withdrawal. It was some time before all elements of the 162nd Infantry could get ready for the withdrawal, and Colonel Haney could not issue orders to execute his plan until 1350.

Ten minutes later all troops had begun moving eastward. The 2nd Battalion, less Company G, loaded on LVT’s and DUKW’s at Parai Jetty, was shuttled to LCM’s and LCT’s lying offshore, and moved back to Bosnek. Company L and part of Company I were withdrawn by the same method. The rest of the 162nd Infantry led by the 3rd Platoon, 603rd Tank Company, moved overland through the Parai Defile and took up positions at Ibdi. The 1st Platoon, 603rd Tank Company, brought up the rear of this echelon. The 2nd Platoon, Company D, 641st Tank Destroyer Battalion, destroyed its mortars and ammunition and moved eastward with the tanks, while the 1st Platoon of the same mortar unit managed to get its weapons out. Company D, 542nd Engineer Boat and Shore Regiment, armed with rifles and light machine guns, was sent up the cliff north of the Parai Jetty as a holding force. After the overland echelons of the 162nd Infantry had moved east through the Parai Defile, the engineer company joined the rearguard tanks and mortar units on the main road.

Close support for the withdrawal was provided by task force artillery and by two amphibious tanks, an antiaircraft LCM (these three manned by the 542nd Engineer Boat and Shore Regiment), and a Seventh Fleet rocket-equipped LCI. By nightfall the 1st Battalion, 162nd Infantry, regimental headquarters, the Cannon and Antitank Companies, a few tanks, the 205th Field Artillery Battalion, Company G of the 186th Infantry, and Company D of the 542nd Engineer Boat and Shore Regiment were in a thousand-yard-long perimeter beginning about 500 yards west of Ibdi. The 3rd Battalion had moved on to Mandom, while the 2nd Battalion remained in the Bosnek area. The 162nd Infantry’s casualties during the day were 16 killed, 96 wounded, and 3 injured. The regiment estimated that it had killed over 500 Japanese during the day. The enemy, despite his losses, followed up the advantage he had gained and quickly pushed troops forward to Parai and into the cliffs along the Parai Defile. This action clearly indicated that the Biak Detachment-intended to take advantage of the natural defensive position in the Parai Defile area.

Preparations for a New Attack: Reinforcement of the HURRICANE Task Force

Even before the 162nd Infantry had been forced to retreat on 29 May, General Fuller had begun to feel that the situation on Biak was serious. He, like Colonel Haney, believed that an advance along the coast to the airdromes would be impossible until the ridges north of Mokmer and Parai could be cleared of enemy troops. The task force commander further considered it impossible, because of the danger of overextending his lines and thereby jeopardizing the beachhead, to outflank the Japanese positions along the ridges unless he could obtain reinforcements. On 28 May General Fuller had therefore asked for at least one infantry regiment, one 105-mm. artillery battalion, a battalion of combat engineers, and another tank company.

General Krueger had already planned to send two battalions of the 163rd Infantry from the Wakde-Sarmi area to Biak to arrive at the latter island on 3 June. Now it was planned to speed the shipment so that the two battalions would reach Biak on 1 June. They were to be shipped from Wakde-Sarmi by LCI and were to carry with them ten days’ rations and three units of fire for all weapons. The additional units that General Fuller had requested could not be dispatched to Biak right away, although one 155-mm. gun battery could be sent immediately. At the same time, General Krueger made plans to move the 503rd Parachute Regiment from eastern New Guinea to Hollandia where it was to remain on the alert for movement by air to Biak in case of need. The ALAMO Force commander also pressed for quick movement of 6th Division units from Milne Bay to Wakde-Sarmi to replace the elements of the 163rd Infantry which were scheduled to leave the latter area for Biak.

Pending the arrival of reinforcements, General Fuller planned to use his available troops to hold the west flank at Ibdi and expand the beachhead at Bosnek. The 162nd Infantry was to establish a semicircular perimeter beginning on the beach west of Ibdi, reaching north to the main ridge, and returning to the beach at the village. The 1st Battalion, 186th Infantry, would maintain a perimeter around Mandom, where Headquarters, HURRICANE Task Force, was located, while the 3rd Battalion moved over the ridge behind Bosnek to set up defenses on the inland plateau. The 2nd Battalion, with part of the 3rd attached, would remain at the Bosnek beachhead. When the first two battalions of the 163rd Infantry arrived, they would take over the 186th Infantry’s beachhead positions, and the beachhead area was then to be extended to include the surveyed airdrome on the flats north of Bosnek. Upon completion of these redisposition’s, the HURRICANE Task Force would make final preparations for a new drive to the west.

On 30 and 31 May the 162nd Infantry patrolled around the main ridge near Ibdi for a route over which large bodies of troops might move north to the inland plateau in preparation for the second attack westward. During the course of this patrolling, it was discovered that the main ridge from Bosnek to the Parai Defile actually comprised a series of seven sharp coral ridges, the crests of which were 50-75 yards apart and separated by gullies 50-100 feet deep. These separate ridges were honeycombed with small natural caves, potholes, and crevices. There was little soil on most of the coral, yet the area maintained a cover of dense rain forest containing trees 8-20 inches thick and 100-150 feet high.

The 162nd Infantry discovered two native trails over the ridges. The most easterly of these, designated “Old Man’s Trail,” began on the beach road about 1,200 yards west of Mandom. It was a fairly well defined track which swung north over the seven ridges along a comparatively easy route. Another track began 1,200 yards to the west, near Ibdi. Called “Young Man’s Trail,” the latter followed a very difficult route over the ridges to the inland plateau. Both of these trails ran through the outer defenses of the Ibdi Pocket, into which the Biak Detachment, on 30 May, moved the 3rd Battalion, 222nd Infantry. On 30 and 31 May the 162nd Infantry’s patrols along the ridges north of Ibdi and Mandom were harassed by the Japanese in the Ibdi Pocket, which had not yet been recognized as a major enemy strong point.

On 30 May the 162nd Infantry located a water hole near the beach terminal of Old Man’s Trail. A regimental water point established there was constantly harassed by Japanese rifle fire from the Ibdi Pocket area or by small enemy parties which moved down out of the ridges north of Ibdi and Mandom. The Cannon Company, 162nd Infantry, was therefore assigned the missions of clearing the enemy from the water point area and protecting that important installation from Japanese attacks.

Halfway through the Parai Defile, a little over a mile west of the 162nd Infantry’s main perimeter, an underground stream ran from the base of the cliff into Soanggarai Bay. At the point where the main road crossed the stream, the 162nd Infantry set up an ambush to prevent Japanese infiltration from the west along the beach. The ambush site was also used as a patrol base from which small parties reconnoitered along the cliffs of the Parai Defile to discover enemy dispositions in the area. Patrolling on 30 and 31 May cost the 162nd Infantry 6 men killed, 17 wounded, and 4 injured.

While the 162nd Infantry had been meeting reverses near Mokmer, the 186th Infantry had been expanding the Bosnek beachhead. On the 28th, patrols secured Opiaref (on the coast about four miles east of Bosnek) where a number of well-prepared but deserted enemy positions were found. Other patrols were sent north to the surveyed drome behind Bosnek. A few Japanese were killed in that area, but no signs of organized resistance were found. Other elements of the regiment patrolled along the ridge north of Ibdi and Mandom, finding that area strongly held, while still more patrols maintained contact with the 162nd Infantry along the coastal road. On 29 and 30 May the 186th Infantry continued patrolling from the Parai Defile east to Opiaref, from which village a motor road was discovered to run inland to the surveyed drome. In all this activity few contacts were made with organized Japanese forces, and during the three-day period the regiment lost but 2 men killed and 18 wounded. [n13-12]

On 28 May the 205th Field Artillery Battalion and the rest of the 947th arrived on Biak. Elements of these two units, together with the 146th Field Artillery Battalion, had moved forward to the Ibdi area to support the drive of the 162nd Infantry and had been withdrawn to Bosnek when the latter regiment was forced back. An antiaircraft battalion (less one battery) and two batteries of another antiaircraft battalion also landed on Biak during the period. These units rapidly went into position to supplement the fires of the antiaircraft units already protecting the beachhead and dump areas. Enemy air raids were a daily occurrence and, although causing little damage and few casualties, demanded augmented antiaircraft protection. The antiaircraft units and Seventh Fleet ships lying offshore shot down most of the enemy raiders.

[n13-12 186th Inf Opns Rpt Biak, 27 May-19 Aug 44, pp. 2-5; Company L, One Hundred and Eighty-Sixth Infantry, APO #41, Rec of Events, Co L, from 25 May 44, p. 1, in ORB RAC AGO collection (hereinafter cited as Co L 186th Inf, Rec of Events, Biak) ; Hist of Biak Campaign, Co K 186th Inf, pp. 1-2, in ORB RAC AGO collection (hereafter cited as Co K 186th Inf Hist of Biak Campaign, and not to be confused with Co K 186th Inf, Rec of Events, 18 Apr-16 Jul 44) ; Co I 186th Inf, Hist of Biak Campaign, n. p., in ORB RAC AGO collection; 1st Bn 186th Inf Hist, 27 May-2 Jun 44, pp.1-3.]

During the period in which the HURRICANE Task Force was awaiting reinforcements, the Biak Detachment redisposed its troops to meet new Allied attacks. The 800 well-armed men of the 3rd Battalion, 222nd Infantry, in the Ibdi Pocket, made only harassing attacks with small groups against the positions of the 162nd Infantry. Colonel Kuzume moved most of his 1st Battalion back into the cave and garden area north of the surveyed strip, a position which the bulk of those units had vacated on 28 May. The 2nd Battalion was left in the Mokmer Drome area to reorganize after its heavy losses on the 28th and 29th and to hold the coastal approach to the airfields. Naval troops and a mortar company of the 2nd Battalion manned the East Caves, north of Mokmer village.

On 31 May the 1st and 3rd Battalions, the Antitank Company, and Headquarters, 163rd Infantry, arrived on Biak. The planned redisposition of the HURRICANE Task Force began immediately and was completed by 1800. The task force was ready to execute a new plan of attack on 1 June.

Plans for a New Attack

Upon the arrival of the two battalions of the 163rd Infantry on Biak, General Krueger radioed to General Fuller that the HURRICANE Task Force was expected to regain the initiative with a new offensive. This offensive, said General Krueger, was to be pushed vigorously “with a view to carrying out your mission effectively and expeditiously.” To execute these instructions, General Fuller planned a two-pronged attack. One regiment, the 186th Infantry, was to advance west over the inland plateau, while the 162nd Infantry was again to attack west along the coast. The two battalions of the 163rd Infantry were to remain in reserve at the Bosnek area. Essentially, this was a return to and an enlargement of the alternative regimental attack plan discarded as unnecessary by the 162nd Infantry on Z Day, 27 May. The 162nd Infantry had originally proposed using battalions as General Fuller now intended to employ regiments.

On 1 June the 3rd Battalion, 186th Infantry, was to move directly over the ridge behind Bosnek to the surveyed airdrome. There it would be joined by the 2nd Battalion, which was to advance west along the inland road from Opiaref, and by the 1st Battalion on the morning of 2 June. Five tanks of the 603rd Tank Company, one platoon of the 116th Engineers, and the 12th Portable Surgical Hospital were to be attached to the regiment. Close support would be provided by the 121st Field Artillery Battalion (75-mm. pack howitzer), which was to follow the 186th Infantry to the surveyed airfield area.

While the 186th Infantry moved into position, the 162nd Infantry was to patrol west along the coastal road and north into the ridges behind Ibdi and Mandom. On 2 June the 2nd Battalion, 162nd Infantry, would move north across the ridge at Ibdi and then west along the inland plateau and ridges, maintaining contact with the 186th Infantry. The rest of the regiment was to push through the Parai Defile again in preparation for another concerted attack toward Mokmer Drome. The 162nd Infantry’s operations were to be supported by Company C, 116th Engineers; seven tanks of the 603rd Tank Company; the 146th and 947th Field Artillery Battalions; Company D, 641st Tank Destroyer Battalion, with 4.2-inch mortars; 1 antiaircraft LCM; two LVT (A)’s, with 37-mm. guns; and two rocket-equipped LCV’s and one LCI (G). The 205th Field Artillery Battalion and offshore destroyers were to be in general support for both regiments.

The 186th Infantry was to sweep the inland plateau and, securing a route over the main ridge north of Mokmer village, clear the high ground north and northeast of Mokmer Drome. The 2nd Battalion, 162nd Infantry, would seize part of the high ground northeast of the airfield. When the other two battalions of the latter regiment, attacking westward along the shore south of the ridge, began approaching Mokmer Drome, the 2nd would aid them in seizing the airstrip. The two battalions of the 163rd Infantry were to protect the beachhead and supply installations and patrol behind the 186th Infantry.

The Seizure of Mokmer Drome Action at the Surveyed Strip At 0830 on 1 June the 3rd Battalion, 186th Infantry, left its bivouac area near Bosnek and marched north over the coastal ridge. By 1100 the unit had reached the west end of the surveyed strip and had set up a defensive perimeter. Company K, together with two guns and crews from the Antitank Company, established defenses at a trail crossing some 400 yards northwest of the rest of the battalion. The 2nd Battalion left Opiaref about 0800 and by 1100 was preparing positions near the center of the surveyed airfield. Company F and the Cannon Company arrived from Opiaref, where they had remained until relieved by the 163rd Infantry late in the afternoon.

The Cannon Company, operating as a rifle unit, protected the 121st Field Artillery Battalion, which had also displaced forward to the surveyed drome. The 1st Platoon, 603rd Tank Company, joined the two battalions of the 186th Infantry at the airstrip about 1530. All these units used the road which ran east and west along the inland plateau on the north side of the surveyed strip. Company B, 116th Engineers, worked all day to repair the road from Opiaref to the forward units. By 1630 the most urgent repairs had been made, and wheeled vehicles could laboriously make their way east along the coast from Bosnek, over the ridge at Opiaref, and thence west to the surveyed area.

The Biak Detachment had no intention of allowing the 186th Infantry to advance unopposed and at 1330 had sent about twenty-five men of the 1st Battalion, 222nd Infantry, against Company K. These Japanese, who were supported by machine guns and mortars emplaced northwest of the trail crossing, continued attacks until 1700, when a platoon of Company K, by a flanking movement, forced their withdrawal northward. Company K and two platoons of the Antitank Company remained at the trail crossing for the night. Company I was moved forward to K’s left and left rear and Company L extended K’s perimeter east along the main road toward the surveyed drome. Battalion headquarters and Company M stayed near the strip’s western end. The 121st Field Artillery Battalion, the Cannon Company, the 2nd Battalion, regimental headquarters, the attached engineers, and the tanks remained near the center of the airfield.

The first part of the night passed without incident, but at 0330 the entire area held by the 3rd Battalion, 186th Infantry, flamed into action. About a company and a half of the 1st Battalion, 222nd Infantry, moved from the south against the semicircular perimeter held by Companies I, K, and L, having outflanked the 3rd Battalion on the west.

Simultaneously, other elements of the 1st Battalion attacked from the northwest, attempting to drive a wedge between Companies L and K. By rapid adjustment of its lines, the 3rd Battalion trapped most of the enemy group which had attacked from the south. Under the support of mortar and machine gun fire from both the northwest and southwest, the encircled Japanese desperately tried to fight their way north. Four hours of confused hand-to-hand fighting, marked by the use of bayonets, machetes, and grenades, ensued. At daylight a count revealed that 86 dead Japanese were within and around the 3rd Battalion’s perimeter. The dead included the commander of the 1st Battalion, 222nd Infantry. Losses to the American unit (including attached Antitank Company men) were 3 men killed and 8 wounded.

Despite the confusion resulting from the night action, the 186th Infantry was ready to resume the westward advance by 0900 on 2 June. The 1st and 3rd Battalions, supported by five tanks and an antitank platoon, were to advance abreast, while the 2nd protected the right flank by patrolling north of the main road. The 121st Field Artillery Battalion was to provide continuous close support and was to displace forward with the infantry. Neither artillery nor air bombardment seems to have been provided for or delivered prior to the attack. However, both the 121st and 146th Field Artillery Battalions (the latter from emplacements south of the ridge, near Bosnek) were registered on targets north and west of the 186th Infantry. Air support was available from Wakde Island upon call.

The speed of the advance was contingent upon the arrival of water from Bosnek and upon improvements which engineers could make on the supply road west of the surveyed drome. The inland plateau was devoid of water, and extensive repairs were necessary before the road could bear wheeled vehicles. Tentatively, the objective for 2 June was set at a point on the road 5,000 yards west of the surveyed strip. Upon reaching this point, the 186th Infantry would be about 1,500 yards north of the 3rd Battalion, 222nd Infantry, which was located in the Ibdi Pocket.

West Toward the Airdromes

The 1st Battalion, 186th Infantry (less Company A, attached to the 162nd Infantry) broke camp at its beach defense area at 0800 on 2 June and moved north over the ridge to join the rest of the regiment. The 1st and 3rd Battalions then advanced with two companies abreast against scattered but determined opposition from elements of the 1st Battalion, 222nd Infantry. Small enemy patrols aimed machine gun and rifle fire at the advancing American units and held their positions until killed or dispersed by tank or artillery fire. Most of the enemy parties were located on the north flank and apparently many of them had been driven westward out of the cave and garden area north of the surveyed drome by fire from the 121st Field Artillery Battalion, which destroyed Biak Detachment headquarters installations in that area. By nightfall the 186th Infantry had killed 96 Japanese and had itself lost 6 men killed and 10 wounded. The unit halted shortly after 1600 and began digging in at a point about 600 yards northeast of the day’s objective. The advance had carried the regiment west until it was almost abreast and north of the 162nd Infantry, at the Ibdi Pocket.

The latter regiment had attempted to move west along the coast from Ibdi during the day. The 2nd Battalion had been dispatched on 1 June into the ridges north of Ibdi with orders to clear Young Man’s Trail and, maintaining contact with the 186th Infantry, advance west along the ridges toward Mokmer Drome. Companies E and G had started over the trail on 1 June and by 1300 had reached the crest of the third of the seven parallel ridges which formed the main ridge above Ibdi. Further progress during the afternoon was rendered nearly impossible by increasingly rough terrain and intensifying Japanese small arms fire, which kept the companies pinned down. Company E remained on the third ridge for the night and set up an outpost at the base of the fourth. The company had bypassed a few small parties of Japanese, while other enemy troops moved around its flanks to cut the trail south of the third ridge. To protect the line of communications over the Young Man’s Trail, Company G moved its forward elements back to the first ridge, and Company F pushed up that ridge to G’s right. Company E was left isolated for the night.

The advance northward had been resumed on 2 June against increasingly strong opposition from the 3rd Battalion, 222nd Infantry, and various service units armed as infantry. Communications between Company E and other elements of the 2nd Battalion were re-established early in the morning, and the company had pushed on to the crest of the fifth ridge by 0930. There the unit was pinned down by enemy fire from both flanks. Company F was ordered forward to E’s right, and arrived on the fifth ridge about 1150. Thereafter, better progress was made as the combined fire power of the two rifle companies kept most of the Japanese under cover. In the afternoon Company G moved forward also and the three rifle companies pushed on over the seventh ridge, bypassing numerous enemy strong points, to establish contact at 1500 with Company E, 186th Infantry, on the inland plateau.

By the time this contact was made, two facts had become obvious. First, it was evident that only by a long series of laborious small unit infantry assaults could the Japanese be cleared from the Ibdi Pocket, which was now recognized by the HURRICANE Task Force as a major enemy strong point. Second, the terrain along the main ridge had been found so rugged that it was evident that no large body of troops could move west along it as long as the Japanese retained any control of the Ibdi Pocket. Therefore the 2nd Battalion (less Company H) was attached to the 186th Infantry for use as the commander of that regiment saw fit. Company H remained south of the ridge.

The addition of the 2nd Battalion, 162nd Infantry, to the 186th Infantry helped to complicate the supply problems of the troops on the plateau. No water had yet been found inland. Heat and humidity were intense, and thick scrub growth, about twelve feet high, stopped any breezes. Despite the best efforts of Company B, 116th Engineers, the supply road could not be repaired fast enough to keep pace with the advancing infantrymen. Water had to be brought around from Bosnek via Opiaref to the forward units, and there were not enough water trailers nor five-gallon cans available to supply all the water needed. At night each man received only one canteen of water for the next day, an inadequate amount under the conditions which prevailed inland. The water situation and the necessity for hauling all other supplies north through Opiaref did more to delay the 186th Infantry’s progress westward than did the opposition of the 1st Battalion, 222nd Infantry.

The advance was to be resumed at 0730 on 3 June, the first objective being the point at which the main ridge left the coast and turned inland near Mokmer village. To gain this point, which lay about three miles west-southwest of the night bivouac, three battalions were to advance along a front 900 yards wide, with the 1st Battalion, 186th Infantry, on the north, the 3rd in the center, and the 2nd Battalion, 162nd Infantry, on the south. The latter unit was to look for trails over the ridge to Parai and was to be ready to cross the ridge to the south upon order from Colonel Newman. The 2nd Battalion, 186th Infantry (less Company F), was to assist the engineers and the 41st Quartermaster Company to move supplies forward. Company F was to be regimental reserve.

The reinforced regiment moved off on schedule, but progress was painfully slow. The road over the plateau deteriorated into a mere footpath, the high scrub growth limited visibility to ten yards, and no landmarks, not even the main ridge along the coast, could be seen from the flat inland plain. Again, no water could be found, although the engineers tried blasting for wells. The 2nd Battalion, 186th Infantry, brought a few supplies forward by hand, and the engineers worked feverishly to extend the road behind the forward troops so that wheeled vehicles could be sent westward: The 2nd Battalion, 162nd Infantry, was unable to find any trails over the ridge to the south. Neither that unit nor the 186th Infantry suffered any battle casualties during the day. The 1st Battalion, 222nd Infantry, had disappeared. Only three Japanese were killed and but few more had been sighted. At 1500 all units began digging in at a point a good half mile short of their objective.

General Fuller instructed the 186th Infantry to send one battalion over the main ridge between Mokmer and Parai on 4 June. The battalion, once over the ridge, was to advance east along the coastal road to take from the rear enemy positions which had been holding up the 162nd Infantry’s advance westward from Ibdi. Colonel Newman replied that all trails leading south from his regiment’s night position had been thoroughly investigated and that none led over the main ridge, the north side of which was precipitous and thus impossible for a large body of men to scale. The regimental commander’s own plan was to move west and slightly north from his night position to find a crossing over the main ridge at some point northeast of Mokmer Drome. One element of his command he planned to send southwest to the bend of the main ridge behind Mokmer village, whence it was to patrol northwest along the ridge toward the rest of the regiment.

Before this disagreement was resolved, General Fuller was prompted to change his orders on the basis of information received from ALAMO Force and aerial reconnaissance indicating that the Japanese were about to attack Biak from the sea. The night of 3-4 June proved quiet in the 186th Infantry’s area, but the next morning’s advance was delayed until supplies and water arrived from Bosnek. Then, about 1000, just as the regiment was starting forward, General Fuller instructed it to hold its positions pending the outcome of the possible Japanese attack. The 186th Infantry there-fore limited its operations to patrolling during which no enemy troops were located. Colonel Newman’s plan for the 5th of June entailed sending three battalions forward toward the north-south section of the main ridge northwest of Mokmer village.

The three units were to halt about 500 yards from the base of the ridge while one company pushed on to find a route up the high ground. As soon as the company’s mission was accomplished, a battalion was to follow it to the ridge top and secure the crossing point. From the crossing, patrols were to be sent north and south along the main ridge.

The 2nd Battalion, 186th Infantry, was to remain in reserve, ready to reinforce any of the three leading battalions or to bring supplies forward. The 121st Field Artillery Battalion, which had already displaced westward once from the surveyed drome, was to move forward again on the 5th. Late at night on 4 June, the threat of Japanese attack from the sea having passed, the G-3 Section of Headquarters, HURRICANE Task Force, gave Colonel Newman permission to execute his plan. Warned by the regimental commander that it was important to secure a foothold on the ridge before the Japanese could deny it to the 186th Infantry, the three assault battalions started westward about 0800 on 5 June. Lack of water again slowed the advance.

No water had been received in the forward area since the morning of the 4th, and Colonel Newman had ordered the troops westward against the advice of his staff and battalion commanders. About noon, however, a heavy rain fell. The regimental commander ordered all troops to halt, catch the rain in ponchos, and fill their canteens. “Had it not been for this lucky break, we would undoubtedly have had to halt in midafternoon.” As events turned out, no Japanese opposition was encountered, and by 1500 the 3rd Battalion, 186th Infantry, was within 500 yards of the main ridge. The 1st Platoon of Company K was sent forward and found a rough approach to the ridge top. Following this route, the entire 3rd Battalion moved up the ridge and dug in for the night. Through the thick jungle growth atop the ridge, the men of the 3rd Battalion could catch occasional glimpses of Mokmer Drome, 2,500 yards to the southwest.

The 2nd Battalion, 186th Infantry (less Companies F and G), moved up to the base of the ridge below the 3rd Battalion to protect the latter’s rear. The 1st Battalion bivouacked near the base of the ridge about 700 yards south of the 2nd, while the 2nd Battalion, 162nd Infantry, remained in the flats 700 yards to the southeast. Company F, 186th Infantry, was placed astride the supply road, 1,000 yards east of the rest of the 2nd Battalion, in order to protect the line of communications. Company B, 116th Engineers, harassed by occasional Japanese rifle fire but protected by Company G, 186th Infantry, labored far into the night to extend the supply road westward to each battalion perimeter. The 121st Field Artillery moved forward again during the afternoon and took up new firing positions about 3,500 yards east of the ridge.

To the Beach

Before his men could start the planned ridge-clearing maneuvers on the morning of 6 June, Colonel Newman received a telephone call from General Fuller which forced the 186th Infantry commander to change his plans. The task force commander ordered the 186th Infantry to seize Mokmer Drome and a beachhead on the coast directly south of that strip. Neither Colonel Newman nor the Assistant Division Commander, Brigadier General Jens A. Doe, liked this plan, for they considered it more important to secure the dominating terrain north and northwest of the airfield before seizing the strip. Colonel Newman put it later: “I objected very strenuously to this plan and told [General Fuller] of my prior planning. However, I was overruled.” But General Fuller was anxious to seize at least one of the airstrips—and according to plans Mokmer Drome was to be the first developed—as soon as possible and, in fact, he was under pressure from General Krueger to do so. His orders stood.

The 186th Infantry’s right flank was to be protected during the move to the airfields by Fifth Air Force aircraft strikes against the Borokoe Drome area, while the 163rd Infantry was to safeguard the line of communications back through the inland flats. As soon as the 186th Infantry secured a beachhead at Mokmer Drome, tanks and general supplies would be sent overwater from Bosnek in preparation for subsequent advances to Borokoe and Sorido Dromes.

Throughout the morning of 6 June the 186th Infantry directed most of its efforts to bringing supplies up to the forward units. Almost the entire 2nd Battalion was engaged in hand-carrying supplies to the 3rd Battalion atop the ridge, while the latter unit sent patrols toward Mokmer Drome seeking good routes of approach to that objective. About noon Colonel Newman reported to task force headquarters that no good route had been found and that supplies, especially the ever-needed water, had not been brought forward in sufficient quantities to allow a regimental attack to be launched that day, and he therefore recommended that the attack be postponed until 7 June. General Fuller approved this suggestion.

About 1430 on 6 June, 3rd Battalion patrols finally found a reasonably good trail leading toward Mokmer Drome and, about the same time, water arrived at the forward area after the long trip overland from Bosnek. At 1500 the 3rd Battalion, followed by the 1st, began moving down the west side of the main ridge to take up positions along a line of departure for the next morning’s attack. The 2nd Battalion, 162nd Infantry, was to follow the first two closely, and the 2nd Battalion, 186th Infantry, was to bring up the rear, after carrying supplies to the top of the ridge. The Cannon, Service, and Headquarters Companies were to aid the 2nd Battalion and were to move with it to Mokmer Drome. The 12th Portable Surgical Hospital (which had been accompanying the 186th Infantry), the Antitank Company, the 121st Field Artillery Battalion, and the regimental trains were to move back to Bosnek. Thence they were to move either along the coastal road or overwater to rejoin the regiment at Mokmer Drome.

In preparation for the infantry attack on 7 June, a thirty-minute artillery concentration began at 0700 that morning. The 146th, 205th, and 947th Field Artillery Battalions, from positions along the coast to the east, were registered on targets in the airfield area ready to support the advance, but most of the firing was undertaken by the 121st Field Artillery from its location behind the 186th Infantry. While the artillery fired on Mokmer Drome and along the low ridge between that field and the 186th Infantry, Fifth Air Force bombers attacked the Borokoe Drome area and also struck some targets along the low ridge. The two assault battalions jumped off at 0730, and by 0850 both had crossed Mokmer Drome and had reached the beach. Neither had encountered any resistance. The 2nd Battalion of the 162nd Infantry arrived at the shore about 0930. The 2nd Battalion, 186th Infantry, together with the Cannon, Service, and Headquarters Companies of the same regiment, all hand-carrying supplies and water, began moving south from their night positions at 0915. All closed at the beach before noon.

When, on 5 June, the 186th Infantry had reached the crest of the main coastal ridge, it had been on the left rear of the Japanese defenses on the low ridge and terraces above Mokmer Drome. Thus, the regiment had been in a favorable position to take these defenses from the rear. But in its move to the airfield, the 186th Infantry had bypassed the Biak Detachment’s principal defensive positions. The bypassing had not been intentional. Colonel Newman had instructed both leading battalions to halt on the low ridge, reconnoiter along it in both directions, and report on Japanese defenses before moving on. According to Colonel Newman: “I received a negative report from both [battalions], and ordered the movement to the airdrome. Evidently, the right [battalion had] failed in this patrolling effort.”

As a result of the failure of reconnaissance on 6 and 7 June to discover the Japanese positions, the 186th Infantry had lost a grand opportunity to outflank the Japanese. Indeed, had even one battalion halted on the low ridge, the story of later operations in the Mokmer Drome area would probably have been far different. Instead, when it reached the beach on the 7th and turned around, the 186th Infantry found itself facing the Biak Detachment’s strongest defenses. As fate would have it, the attacker had placed himself where the defender most wanted him to be. This was soon to become obvious.

No fire had been received by the 186th Infantry from the Japanese ridge and terrace positions during the advance south to the beach, nor had any fire come from the Japanese in the East Caves area, the source of trouble to the 162nd Infantry during the first, abortive attempt to seize Mokmer Drome. But suddenly, about 0945 on the 7th, the entire Mokmer Drome area was subjected to Japanese artillery, antiaircraft, mortar, and automatic weapons fire from the northwest, north, northeast, and east.

This fire, coming from emplacements which were well-camouflaged, concealed in dense scrub growth, or protected in defilade or caves, continued for about four hours. Almost all the HURRICANE Task Force’s artillery was called upon to fire on known or suspected Japanese installations in the area, while the 186th Infantry’s mortars blasted away whenever a Japanese gun flash disclosed the location of a position. Japanese mortar and 20-mm. fire from the area of the East Caves was especially troublesome, for the task force’s artillery could not reach those weapons. From the northwest, along the low ridge beyond the West Caves, came 75-mm. artillery or dual-purpose antiaircraft artillery fire, the point of origin of which could not be located.

The 121st Field Artillery fired over 2,000 rounds during the 7th, and it adjusted fire for the 205th and 947th Field Artillery Battalions, also engaged in the counterbattery fire. Late in the afternoon it was estimated that the Japanese fire had been decreased by about 40 percent. At least six enemy gun positions had been silenced and mortar fire had become lighter. Before dark the Japanese, apparently feeling that they had received enough counter-fire, began moving to new locations most of the mobile weapons they had emplaced north of the airdrome. Indications were that HURRICANE Task Force artillery would probably be called upon for heavy concentrations again on the 8th.

Meanwhile, the 186th Infantry had completed occupation of the airdrome area and had organized the beachhead, flushing a few Japanese from small caves along the shore line. It had been planned that the 2nd Battalion, 162nd Infantry, would push east from the airfields to aid its parent regiment to eliminate Japanese resistance at the Parai Defile. However, Japanese in the East Caves covered the road from Mokmer Drome to Parai with automatic weapons fire. Colonel Newman therefore recommended to Headquarters, HURRICANE Task Force, that the 162nd Infantry’s battalion remain in place until this fire could be reduced. He pointed out, moreover, that the 186th Infantry did not have enough rations or ammunition to supply such an attack. General Fuller approved this recommendation and the battalion remained at the Mokmer Drome beachhead for the night.

By evening of the 7th, it had become impracticable to supply the 186th Infantry over the inland plateau road, which ended on the east side of the main ridge. From that point all supplies would have to be hand-carried to Mokmer Drome, and supply parties would be endangered by Japanese patrols, a few of which moved in behind the 186th Infantry as the regiment moved to the beach. Overwater supply appeared easier, and the main supply line was therefore changed to a water route which ran from Bosnek to the village of Sboeria, located on the beach south of Mokmer Drome.

The first attempt to run supplies over this water route was undertaken during the late afternoon of 7 June by three LCM’s and a few LCV’s, each of the former carrying a Sherman tank. These craft were supported by an antiaircraft LCM and an LCS, and all were manned by the 542nd Engineer Boat and Shore Regiment. As the first boats approached the shore they were greeted by machine gun and rifle fire from Japanese whom the 186th Infantry had not yet cleaned out of caves along the water line in front of Mokmer Drome. The small craft returned the fire, but were finally forced to withdraw. The 186th Infantry, according to Colonel Newman, was “glad to see them withdraw since they had our troops running for cover.”

At 1400 another attempt was made to land supplies at Sboeria. The three LCM’s managed to put their tanks ashore in the face of continuing Japanese fire, but accompanying LCT’s were driven off by Japanese artillery. Two of the LCM’s were so damaged by enemy fire that they could not fully retract their ramps and had to proceed the nine and a half miles back to Bosnek in reverse. Plans were made to effect all delivery of supplies and evacuation of casualties at night until the enemy fire on the Sboeria beachhead could be neutralized.

The tanks which had been landed lumbered along the shore road fronting Mokmer Drome, destroying several small bunkers along the beach. Then they wheeled toward the low ridge north of the airfield, taking under fire a Japanese 75-mm. mountain gun and a 20-mm. piece which had opposed their landing. These two weapons were silenced. Moving cautiously northwestward from the field along a road which crossed the low ridge, the tanks destroyed two large pillboxes. By the time this operation was completed, dusk was approaching, and the tanks returned to the beach to bivouac with the 186th Infantry.

The regiment dug in along a semicircular perimeter. The 3rd Battalion was on the western edge of Sboeria, extending from the beach to the south side of the airfield, while the 1st Battalion occupied a similar line east of Sboeria. The 2nd Battalion, 186th Infantry, and the 2nd Battalion, 162nd Infantry, were between the first two, but on the north side of the field. As night fell, the enemy fire slackened and a count could be made of casualties. It was found that the day’s operations had cost 14 men killed and 68 wounded, almost all as a result of Japanese artillery and mortar fire.

During the night of 7-8 June more badly needed supplies were brought forward to Sboeria by small craft of the 542nd Engineer Boat and Shore Regiment in an operation concerning which widely different stories are told. According to the engineers’ reports, no one from the 186th Infantry was on hand at the beach when, about 2330, a convoy of 1 LCS, 14 LCV’s, and 8 LVT’s arrived at Sboeria. After waiting almost half an hour for unloading aid, the engineers transferred the LCV cargo to LVT’s which pushed ashore and finally found some representatives of the 186th Infantry, who were eagerly awaiting the rations and ammunition.

The commander of the 186th Infantry tells a different tale: I personally was at the beach, with my S-4. . . . We had given Division Headquarters flashlight recognition signals, but evidently these were probably not communicated to the boat group commander. . . . They [the boats] did not reply to our signals and proceeded on down the coast before returning and sending in the LVTs. Failure to properly coordinate signals and over caution on the part of the boat commanders was apparently responsible. . . .Whatever the case, the welcome supplies were put ashore, and the LVT’s returned to Bosnek with the most seriously wounded men of the 186th Infantry.

Thus, by daybreak on 8 June, the 186th Infantry was firmly established on Mokmer Drome, and, despite difficulties incident to moving supplies forward by water from Bosnek, it was obvious that the regiment could be supplied. The first of the three Japanese airfields on the southeast shore of Biak had been seized, but the area north of the airfield had not yet been secured. Until it was, Mokmer Drome could not be repaired and Allied planes could not use the field.

Source: Approach to the Philippines: BY; Lieutenant Colonel Robert Ross Smith (Ret.) (United States Army Center of Military History)

World War Two: Biak: Frustration at Mokmer Drome (AP-14)

World War Two: Biak: The Plan, the Landing, the Enemy (AP-12) May 1944


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