Last time we spoke about liberation of Luzon.. American forces, led by General Eichelberger and supported by General Krueger's armies, relentlessly advanced against the entrenched Japanese defenders of General Yamashita’s 14th Area Army. Amid thick jungle and treacherous terrain, battles raged through the northern mountain ranges, as American troops aimed to restore the Filipino government. Facing overwhelming odds, the Japanese forces displayed extraordinary resilience, temporarily halting American progress. Remarkable efforts from General Swift’s 1st Corps across Routes 9 and 11 led to significant breakthroughs as American forces captured critical positions, including Sablan and Baguio. However, the Japanese command, complacent and misjudging the American strategy, fell into disarray. As the tide turned with relentless American assaults, key Japanese positions were systematically dismantled. By late April, most of Luzon was liberated, restoring hope and autonomy to the Filipino people.
This episode is Invasion of Balikpapan
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The battles for Okinawa and Luzon just closed up, and today we are going to be venturing back to the Dutch East Indies. As we left off in mid-May, the tides of war were shifting dramatically on the island of Luzon, with General Krueger's 6th Army celebrating significant victories across the region. In the north, General Swift’s 1st Corps had successfully secured the scenic Baguio area, known for its lush mountains and cool climate, a stark contrast to the tropical heat that engulfed much of the Philippines. Yet, the fighting was far from over, as fierce battles continued on three major fronts. Colonel Volckmann’s guerrilla 121st Regiment was making strides, snagging much of the strategically vital Bessang Pass, a crucial artery connecting northern Luzon to the central regions. However, their success came at a cost, leaving them overextended amidst fierce Japanese resistance. Meanwhile, General Gill’s weary 32nd Division managed to claim dominance over the rugged terrain of Salacsac Pass along the historic Villa Verde Trail, known for its breathtaking views and treacherous paths that had challenged both soldiers and their supply lines.
General Mullins’ 25th Division achieved a remarkable breakthrough by capturing the key Balete Pass, opening the way for further advances. Not stopping there, the 25th Division pressed onward, quickly redirecting their focus northward towards the town of Santa Fe. By May 24, the 27th Regiment had cleared the Sawmill River valley, an area teeming with dense foliage and rugged hills, a significant accomplishment that paved the way for the next objectives. From there, the 1st Battalion expertly maneuvered eastward against the imposing Kanami Ridge. On May 22, the 161st Regiment dealt a heavy blow to Japanese positions in a stronghold on Mount Haruna, a location known for its steep, challenging slopes. Following this triumph, they began their descent down the northern slopes of Haruna Ridge, gearing up for a critical junction with the Villa Verde Trail by May 27. Meanwhile, the 35th Regiment launched a vigorous assault from Balete Pass, systematically clearing out the remaining Japanese caves and fortifications by May 26, culminating in the capture of Santa Fe the very next day. At Salacsac, the Japanese forces, led by General Iwanaka, initiated a limited counteroffensive, presumably to buy time for a strategic evacuation of their increasingly tenuous positions. If delay was indeed Iwanaka's intention, he executed it well; it wasn’t until May 19 that the American supply line was finally deemed secure again. The 2nd Battalion of the 128th Regiment resumed its push east from Hill 525, but the progress was slow. By May 22, the 1st Battalion had only managed to advance a mere 500 yards east from Hill 508, while the 3rd Battalion commenced a southward and southeastward advance from Hill 516 on May 16. It was not until May 24 that the relentless fighting in the region bore fruit, leading to the eventual clearing of the area, and Salacsac Pass was officially declared secured.
On that pivotal day, General Iwanaka began the difficult task of withdrawing the remnants of his battered forces northward, retreating up the winding valley of the Imugan River. This river, which flows through a lush, verdant landscape, would serve as a vital sanctuary, albeit one fraught with danger for the disheartened Japanese troops. Meanwhile, the American forces were gaining ground. The 2nd Battalion aggressively seized control of Hill 527, a position that provided a commanding view of the surrounding area, crucial for planning further advances. The 126th Regiment took decisive action, utilizing trucks to transport troops swiftly along Route 5 to Balete Pass before launching an assault toward Imugan from the east and southeast. Concurrently, the guerrilla 1st Battalion of the Buena Vista Regiment embarked on a northward push from Valdez, culminating in the hard-fought capture of Hill 528 on May 28. This hill, commanding and steep, presented a formidable challenge but also promised a vantage point critical for any further operations in the region. The very next day, Imugan finally succumbed to the relentless pressure of the advancing American forces, marking a significant milestone as the Villa Verde Trail came firmly under American control. This development effectively concluded the arduous operations of the 32nd Division. It was a costly campaign for General Gill; the division suffered approximately 825 men killed, 2,160 wounded, with an alarming 6,000 classified as non-battle casualties. In stark contrast, the Japanese defense was decimated, with at least 5,750 of the 8,750 troops they had deployed to defend the trail lying dead.
As we gaze northward, we find Colonel Volckmann’s guerrillas, who had extended themselves too thinly across Bessang Pass and into the challenging terrain of Yubo Ridge. The aftermath of their overreach saw them facing fierce Japanese counterattacks that swiftly pushed them back across Lamagan Ridge in the latter part of May. However, a small contingent managed to hold tenaciously onto the eastern slopes of Langiatan Hill, a strategic position that allowed them to maintain some level of influence in the region. Additionally, a robust force from the Japanese 76th Regiment assembled south of Butac, planning an offensive northward. However, this advance was met with fierce resistance from the guerrilla 15th Regiment, who successfully repelled the attack. Seizing the momentum, Volckmann directed the 15th Regiment into a new offensive eastward, and by the end of May, they had successfully re-secured their foothold up to Lamagan Ridge. Meanwhile, elements of the 121st Regiment executed a remarkable retaking of both Langiatan Hill and Yubo Ridge, gradually restoring control over this strategically vital area. Looking south, we find General Hall's 11th Corps vigorously engaged in two crucial offensives aimed at capturing Ipo Dam and Wawa Dam, both essential water reservoirs located east of Manila. The strategic importance of these dams cannot be overstated; they were vital not only for securing fresh water but also for controlling the flow of operations in the region. However, the relentless heavy downpours that characterized the season rendered air support missions impractical, exacerbating an already challenging supply situation for the advancing troops. As a result, General Wing’s 43rd Division was forced to pause its offensive late on May 14 to reassess and devise new attack plans.
As of late May 14, the 43rd Division found itself in a precarious situation, necessitating a halt to operations to devise new attack plans. To this point, the division had made limited progress toward securing Route 52, a crucial supply line vital for their mission to capture Ipo Dam. Recognizing the urgency, General Wing decided it was essential to commit the 169th Regiment to a targeted attack to clear this road, as it would serve as a critical route for both supply and evacuation in the coming days. The adverse weather conditions had created a significant operational hindrance. For nearly the entire duration of their offensive, intermittent rains had severely disrupted ground and aerial supply chains, as well as evacuation and the crucial air support operations necessary for a successful advance. Ground conditions had become challenging, and division engineers struggled to construct and maintain supply roads at a pace even close to that of the infantry's advances. Consequently, supply drops and hand-carried provisions were just sufficient to keep combat units barely above the minimum required levels, but the evacuation of sick and wounded soldiers remained a pressing issue that plagued the division. By May 14, the situation worsened significantly. For the first time since May 6, the 5th Air Force was completely grounded, unable to conduct any air support or supply missions due to the worsening weather conditions. This represented a troubling turning point for the 43rd Division. Moreover, intelligence reports indicated that sizable groups from the Japanese Tomono and Hanabusa Detachments had shifted their focus away from their defenses along Route 52, moving instead to confront the 103rd and 172nd Regiments attacking from the south. General Wing recognized that this presented a timely opportunity for the 169th Regiment. Striking directly along Route 52 would likely be far easier and less costly than it would have been just a week prior. Furthermore, a successful offensive by the 169th could not only expedite the capture of Ipo Dam but also prevent further eastward redeployments of Japanese forces. This would be a vital maneuver, potentially relieving pressure from Fork Ridge, where the left flank of the 172nd Regiment was currently bogged down in fierce fighting. Time was of the essence, and decisive action was required to turn the tide in favor of the 43rd Division.
The situation was critical; delay would allow Japanese forces to fortify their defenses further. In response, Wing mapped out a robust plan: he directed the 103rd Regiment to capture the Route 52 terminus at Ipo Dam itself, which was crucial for any further advances. Their orders included not only taking control of the dam but also clearing the high ground north of the road and west of the dam to ensure a secure position against any possible counterattacks. Additionally, he tasked the 172nd Regiment with seizing Hill 804, a vantage point that could provide vital intelligence and support to the offensive, while the 169th Regiment was directed to eliminate the last Japanese defenders in the Bigti area before advancing eastward along Route 52 to connect with the 172nd. A break in the weather finally came on May 17, allowing the 43rd Division to launch their offensive with much-needed air support. Aircraft successfully dropped napalm and strafed Japanese defensive positions, a strategy that proved devastatingly effective. General Kawashima, facing mounting losses, ultimately ordered the remnants of his command to withdraw to an assembly point on the western slopes of Mount Maranat, a retreat that revealed their deteriorating ability to hold the line. With the air support providing a critical advantage, the 103rd Regiment advanced boldly and swiftly cleared the last Japanese holdouts from Hill 860, securing an essential position. However, it was the guerrilla forces, under the command of Colonel Augustin, from the Marking Regiment who achieved a historic victory by capturing Ipo Dam shortly after noon. His patrols descended the slopes of Hill 803, crossed the Angat River at the dam, and triumphantly raised the American flag over the powerhouse on the south bank, a potent symbol of liberation and resistance. Simultaneously, the 172nd Regiment seized control of Fork Ridge, further tightening the noose around Japanese forces, while the 169th Regiment secured strategic ground from Hill 535 to Osboy Ridge, pushing forward with relentless determination.
In the following four days, the 43rd Division, supported by the fearless Marking guerrillas, meticulously mopped up the area west of Ipo Dam. Their efforts culminated in the successful opening of Route 52 from Bigti to Ipo on May 19, a critical milestone that allowed for the unhindered movement of troops and supplies. By May 21, they completed the operation by clearing out the last pockets of organized resistance in the region west of the dam and south of the Angat River, a crucial waterway that would play a significant role in sustaining American operations. With the capture of Ipo Dam intact, General Wing achieved his primary objective, making a significant contribution to addressing Manila's pressing water supply problems. This success would have lasting implications for the civilians and military alike, as the dam was key to ensuring a reliable water supply in the region. The 43rd Division maintained its momentum, continuing mopping-up operations through May 31. They patrolled eastward across the Ipo River, pressed northeast up the Angat from the dam, and scoured the areas that had witnessed some of the most intense fighting during the campaign. The cost of these operations was notable; Wing’s forces suffered losses of 120 killed and 515 wounded, while the Kawashima Force endured devastating casualties, with over 2,700 men killed and approximately 115 captured during the grueling battle.
Meanwhile, General Chase's 38th Division pressed forward with its offensive against Wawa Dam, following the failure of General Yokoyama’s most recent counteroffensive. The 145th Regiment found itself holding a precariously exposed salient at Mount Binicayan, which severely hampered their ability to launch an effective attack toward Wawa Dam. Japanese positions on the high ground to the north of the dam dominated the narrow, winding road with artillery, mortar, and machine-gun fire, making any advance perilous. In response to this daunting challenge, General Chase decided to launch an offensive with the 151st Regiment in the area north of the Marikina River, targeting the formidable Mounts Pamitinan and Hapanong-Banoy. This bold maneuver was contingent upon the 152nd Regiment gaining momentum in its attack to clear Woodpecker Ridge. As such, on May 19 and 20, the 152nd Regiment executed enveloping maneuvers centered on Woodpecker Ridge, ultimately breaking through enemy lines on May 21. The breakthrough was dramatically supported by the introduction of medium tanks and flamethrower tanks, powerful assets that helped turn the tide of battle. The following day, what began as a breakthrough rapidly escalated into a rout of Japanese defenders. By May 25, the 152nd Regiment had established control over the strategic junction of the Marikina and Bosoboso Rivers, a key position that not only bolstered their operational capabilities but also positioned them for further advances in the ongoing campaign.
As Japanese resistance began to dissipate under the relentless pressure from the advancing American forces, the 149th Regiment, which had successfully relieved the 145th at Mount Binicayan, launched a bold strike toward Wawa Dam on May 27. Encountering little to no opposition, they secured the dam intact the following morning, marking a significant victory. It was on May 27 that General Yokoyama ordered a general retreat, recognizing the untenable position of his forces. Acting on these instructions, General Kobayashi's remaining troops fell back, pursued by vigilant patrols from the 38th Division. With Wawa Dam secured, General Chase shifted his strategy; rather than launching direct assaults against organized Japanese lines, he opted to focus on mopping up operations and pursuing the retreating enemy. The human cost of the campaign was significant. Chase’s forces sustained losses of 160 killed and 590 wounded, while the Kobayashi Force suffered catastrophic losses, with over 10,000 men killed since the onset of the offensive.
Shifting focus southeast, the 7th Cavalry and Lieutenant Colonel Bernard Anderson’s guerrillas converged on the coastal town of Infanta in late May. Faced with overwhelming pressure, the Japanese naval garrison retreated westward into the Sierra Madre mountains, a rugged and dense area that posed challenges for both sides. Infanta ultimately fell on May 25, and by the evening of the following day, the reinforced 7th Cavalry had successfully cleared the entire flat, rice-rich region surrounding the town, encountering only scattered and ineffective resistance. In a strategic move bolstered by overwater supply movements, the 7th Cavalry implemented an aggressive patrolling program to the southwest, seeking out any remaining enemy forces. Meanwhile, the 8th Cavalry focused its efforts on clearing the northern section of Santa Maria Valley, advancing northward into the Sierra Madre. By the end of May, the Shimbu Group, once a significant Japanese fighting force, was rendered ineffective. Its main units began to disband, breaking into small groups in a desperate bid to forage for food or to navigate their way to safety in northern Luzon.
At the end of May, the Shimbu Group still boasted a strength of nearly 26,000 men, over half of its total personnel as of February 20. However, the remaining survivors were not the elite forces they once were. The relentless campaigns by the 11th and 14th Corps had decimated the best-trained and most well-equipped units, leaving behind a shell of what had once been a formidable fighting force. Of the approximately 13,000 survivors still organized into units, their combat effectiveness had deteriorated so significantly that it's worthy of mention only in passing. Meanwhile, about 13,000 others were struggling to survive without proper organization; roughly 5,000 of these were receiving whatever limited medical treatment the Shimbu Group could provide. The remaining 8,000 men had essentially lost all structure, scattering into small groups to forage for food or attempting to make their way north to Luzon, where they hoped to find safety and sustenance.
The supply situation faced by the Shimbu Group at the end of May was even more dire than its personnel situation. They had been unable to transport significant portions of their vast stockpiles of supplies into the Sierra Madre mountains, a shortfall that would prove catastrophic for their survival. The only supplies they still possessed in any quantity were ammunition for small arms and machine guns, alongside medical materials for treating combat wounds. The most pressing issue, however, was a critical lack of food. The early loss of several key agricultural regions, including the Bosoboso Valley, the shores of Laguna de Bay, the Santa Maria Valley, and the fertile Infanta region, had deprived the Shimbu Group of expected food stocks. Most of the supplies brought out of Manila had already been consumed. For instance, the organized remnant of the Noguchi Force could currently allocate a meager two ounces of rice per day for each man—a portion that would undoubtedly vanish by mid-June. The Kobayashi Force fared little better, while the Kawashima Force managed to issue slightly more, around six to eight ounces of rice daily. The troops were gradually reduced to scavenging for survival, resorting to eating roots, bark, grass, and whatever food they could find in long-abandoned Filipino gardens. It’s worth noting that after just a few days in June, there wasn’t a single pig, carabao, or dog left alive within sight of the remnants of the Shimbu Group. Recognizing that mere existence was the overarching challenge, General Yokoyama hoped to regroup his organized units and move them into areas where they might have some chance to cultivate food, scattering them through the challenging terrain of the Sierra Madre. This desperate strategy highlighted the dire straits faced by the Shimbu Group as their chances for survival dwindled.
Meanwhile, the Noguchi Force received orders to transfer its main strength to the mountainous region along the eastern shore of Laguna de Bay, where some of its elements were already positioned. This shift aimed to gather their forces in a more favorable terrain, potentially allowing for better access to resources. The Kobayashi Force was tasked with establishing a defensive sector in the area north of Mount Purro and east of Wawa. In a coordinated effort, the 31st Infantry, minus its 3rd Battalion, along with various miscellaneous troops from the 8th Division, were ordered to occupy positions north of the Lenatin River, enhancing their defensive capabilities in a strategic location. The remnants of the Kawashima Force, already in the process of withdrawing from the Ipo Dam area, were instructed to relocate to the mountains east of San Miguel, approximately 22 miles northwest of Ipo. This area was believed to have more abundant food supplies, crucial for the survival of their forces. However, as circumstances unfolded, this transfer later proved impossible. Unable to move effectively, the bulk of the Kawashima Force remained entrenched in the area surrounding Mount Inuman, where they faced mounting challenges in sustaining their troops.
In the following month, General Hall directed the 38th Division and Major Edwin Ramsey’s 2nd Provisional Regiment to pursue the remnants of Yokoyama’s forces as they moved eastward toward Santa Iñez. Meanwhile, the 112th Cavalry employed various mountain and river valley trails to mount a converging attack from the south. They encountered light opposition and successfully captured the town on June 9, further consolidating their gains in the region. At the same time, patrols from the 43rd Division reported no signs of organized resistance north and east of Ipo Dam. The 2nd Cavalry Brigade, alongside Anderson’s guerrillas, effectively dispersed the last organized remnants of the Kogure Detachment and the remaining Japanese naval units at Lamon Bay. By the end of June, the only indication of organized Japanese resistance in an area extending five miles north and ten miles east of Wawa Dam was found in the Lenatin River valley, approximately three miles north of Santa Iñez. This development forced the remnants of Yokoyama’s forces into trackless and only partially explored wilderness, significantly complicating their ability to regroup or launch further operations. The operations throughout June were costly for Hall, resulting in approximately 110 men killed and 370 wounded. In contrast, Japanese losses during the month were staggering, amounting to 7,540 killed or found dead, alongside 1,105 captured.
Looking back north, General Yamashita aimed to avoid a similar fate for his northern forces. Ever since the fall of Baguio, he had been meticulously planning for the ultimate withdrawal of the Shobu Group deep into the Cordillera Central. On May 5, less than two weeks following the fall of Baguio, General Yamashita disseminated an outline plan for future operations to the major components of the Shobu Group throughout northern Luzon. His strategy was built on three fundamental premises: Estimation of Enemy Actions: Yamashita assessed that the 6th Army would concentrate its main effort on a northward drive along Route 5, anticipating that General Krueger would only launch secondary attacks toward Bontoc via Routes 4 and 11. This understanding allowed him to anticipate the flow of enemy movements and allocate his resources more effectively. Timing for Resource Stripping: He calculated that the Shobu Group would have approximately three months during which it could strip the Cagayan and Magat Valleys of the essential food and military supplies needed for a protracted stand in the mountains. During this period, the group aimed to transport this matériel into the Cordillera Central through the junction of Routes 4 and 5, located near Bagabag, 25 miles north on Route 5 from Bambang. Control of Key Routes: Yamashita recognized that the success of his planned withdrawal and future delaying actions hinged on maintaining control over the Routes 4-5 junction for as long as possible. He estimated that his defenses south of Santa Fe would be robust enough to hold until mid-June. Additionally, he planned to construct new defensive positions across Route 5 between Santa Fe and Bambang, enabling him to contain the 1st Corps south of Bambang until the end of June. Most crucially, he believed that he would be able to retain control of the Junction of Routes 4 and 5 until the end of July, which was essential for his operational strategy. His initial perimeter encompassed the vital Route 11 terminus of the Baguio-Aritao supply road, as well as key locations such as Bessang Pass, Bontoc, Banaue, Oriung Pass, and Santa Fe In his May 5 plan, Yamashita outlined the necessity of holding the Salacsac Pass-Balete Pass line until mid-June while constructing additional defenses between Santa Fe and Bambang. After mid-June, the Japanese forces were to withdraw to a second perimeter, extending through Ambuclao, Mankayan, Sabangan, Bontoc, Oriung Pass, and Bambang, strategically positioning themselves for potential future engagements.
Yamashita understood that these defenses would need to hold until July, when the defenders would be expected to retreat to his last-stand positions centered around Bokod, Mankayan, Polis Pass, the Rayambugan Farm School, and Bambang. He anticipated that the Shobu Group would be compelled to hold their ground until annihilation at these key locations. On April 27, the 103rd Division received orders from the Area Army to transfer its main strength to the Cauayan-Cabagan area, leaving behind only the Yuguchi Detachment 80th Brigade Headquarters in Aparri, which comprised a meager two battalions of nuclear infantry. Yamashita’s plans called for virtually abandoning the Cagayan Valley, temporarily retaining only the 103rd Division, which was significantly outnumbered and equated to less than two American Regimental Combat Teams (RCTs), particularly since the Araki Force was stationed in the Cervantes area.
The primary duty of the 103rd Division would be to gather all available resources in the valley, including rice and livestock such as carabaos, and dispatch these supplies into the Cordillera Central through Bagabag. Once this crucial task was completed, the division would also withdraw into the mountains, aligning with Yamashita’s broader strategic objectives. Yamashita’s decision to abandon the Cagayan Valley made logical sense. He realized that the forces he had remaining could not hold the valley for much longer. Additionally, there seemed little necessity to maintain a strong presence there any further. Initially, he had kept units in the valley to harvest and gather food, deny the Allied Air Forces of the Southwest Pacific Area (SWPA) the use of airfields for strikes against Formosa and Okinawa, and hold onto Aparri in the hope that supplies and reinforcements might still reach Luzon. However, by early May, Yamashita concluded that the situation at Okinawa was largely resolved, negating any strategic purpose behind holding the valley airfields. The hope for reinforcements had long since faded, and crucially, his troops had already gathered the early rice harvest from the valley. With no new crop expected to come in until late September, Yamashita recognized that he would not be able to harvest this future crop, further solidifying his decision to withdraw. Yamashita also ordered the 79th Brigade to take over the defense of Banaue, while directing the 105th Division to defend both the Magat Valley and the Bato Bridge area against potential airborne attacks. However, by the end of May, the situation deteriorated significantly: Santa Fe had fallen, and the retreat of the 10th Division had devolved into a chaotic rout. This development put the defenders at risk of allowing the enemy to reach Bambang before they could establish any strong delaying positions south of the town.
In response, Yamashita ordered the 10th Division and the 2nd Tank Division to assemble for a defensive stand across Route 5 at Bato Bridge. He also repositioned the 105th Division to the Rayambugan Farm School and directed the 103rd Division to occupy the vacated defenses at Oriung Pass. Despite these strategic maneuvers, time was not on their side. General Krueger wasted no time launching an aggressive pursuit northward, immediately sending the relatively fresh 37th Division to drive straight up Route 5 from Santa Fe to Bagabag. This force was then to swing east through Oriung Pass into the Cagayan Valley, continuing its advance north along Route 5 toward Aparri. To prepare for a larger offensive, Krueger also intended to use the 25th and 33rd Divisions in the initial assault against the Japanese home islands. To this end, he directed the 32nd Division to take over operations in the Baguio area, while the 6th Division was tasked with relieving the 25th at Santa Fe before striking northwest up Route 4 into the deep Cordillera Central, pursuing the Japanese forces further into the mountainous terrain.
Finally, Swift was ordered to execute limited attacks up Route 11 from Baguio, maintain the guerrilla offensive against Cervantes, and deploy the Connolly Task Force to follow Route 3 around the northwest tip of Luzon to secure the Aparri region. Leading the charge, the 129th Regiment of the 37th Division advanced north from Santa Fe on May 31, quickly encountering a reinforced provisional anti-tank unit just south of Aritao. This unit managed to delay the town's capture until June 5. However, the following day, Bambang fell without resistance, and the 129th faced only token opposition at Bato Bridge before ultimately reaching Bayombong on June 7. On June 8, the 145th Regiment took over the lead, and by nightfall, they had seized the crucial junction of Routes 4 and 5 near Bagabag without a fight. Advancing further, the 145th crossed the Magat River on June 9 and pressed toward Oriung Pass, where they rapidly engaged the reinforced 179th Independent Battalion. Although the outgunned and outnumbered defenders valiantly delayed the advance, the 145th pushed through the pass along Route 5 and secured it late on June 12. This breakthrough prompted the bulk of the 103rd Division to decide on a strategic retreat toward the Bontoc-Natonin area, while the remnants of the 4th Air Division abandoned Echague to join this withdrawal. By the evening of June 13, the 145th finally halted its advance at Santiago, while the 148th Regiment worked to neutralize the remaining Japanese positions at Oriung Pass. With these positions secured, the offensive resumed, resulting in the fall of the Echague airbase on June 14, followed by the occupation of Cauayan two days later.
As we can see, neither the 10th Division nor the 2nd Tank Division managed to reach Bagabag in time to impede the American advance; the latter was assembling along the Bambang-Pingkian road. On June 12, the 20th Regiment initiated a southwest drive along this road from Bambang. Two days later, elements of the 126th Regiment began pushing west toward Pingkian from Aritao, thereby applying significant pressure on Iwanaka’s beleaguered troops. Meanwhile, the 10th Division had become hopelessly cut off east of Route 5 and had retreated to the Old Spanish Trail south of Aritao. On June 11, the 25th Division launched a two-pronged attack against this isolated group, forcing General Okamoto’s remnants to retreat eastward deep into the Sierra Madre. In the meantime, General Clarkson dispatched the 130th Regiment up Route 11, where they encountered the 58th Independent Mixed Brigade, which was only capable of weak resistance. Poor weather conditions hindered the 33rd Division's operations in the following days, but by June 15, elements of the 130th Regiment had swung east along the Baguio-Aritao supply road and reached Ambuclao on the Agno River. To the north, Volckmann continued his offensive throughout June, deploying the 121st Regiment to clear Route 4 and secure the northern half of Lamagan Ridge. The 15th Regiment was tasked with advancing to seize Upper Cadsu Ridge and then moving generally northeast along the south side of Route 4. Additionally, the still-arriving 66th Regiment aimed to secure the area south of Butac and swing to the east on the 15th's right flank. As a result, both Lamagan Ridge and Lower Cadsu Ridge were cleared by June 5, with the 15th Regiment then turning its focus toward Upper Cadsu while the 121st Regiment advanced directly toward Bessang Pass.
Volckmann’s Provisional Battalion launched an attack on Magun Hill and, after a series of minor setbacks, succeeded in clearing much of the area by June 10. On that day, the 121st Regiment initiated a final assault toward Bessang Pass, advancing from the west and southwest. The following day, the Provisional Battalion began pressing in from the north and northeast. Meanwhile, the 15th Regiment overran the last organized resistance on Upper Cadsu on June 12, just as the 66th Regiment was reaching the southwestern corner of the ridge. Supported by artillery, the 121st finally overcame the last organized defenses at Bessang Pass on June 14, establishing contact with the Provisional Battalion east of the pass. On the same day, the final pockets of opposition crumbled before the 15th and 66th Regiments south of the pass. Consequently, the remnants of Japanese forces fled east along Route 4 toward Cervantes, pursued by elements of the 15th and 121st Regiments, which successfully secured the town before dark on June 15. During this final offensive, the guerrillas suffered losses of 119 men killed and 120 wounded, while exaggerated estimates placed Japanese losses at around 2,600 killed. At the same time, by mid-June, the guerrilla 11th and 14th Regiments had cleared almost all the valley west of the Cagayan River, stretching from Cauayan north to Aparri. They also gained complete control over Route 11 from Bontoc to the valley, effectively preventing the 103rd Division from joining Yamashita’s last-stand positions. Meanwhile, the Connolly Task Force, after a largely uneventful march, approached Aparri and began an attack on June 11 to clear the last Japanese forces from the area. The last event forcing Yamashita to alter his plans came on 13 June, when the 6th Division's 63d Infantry began probing northwest up Route 4 from Bagabag. The reconnaissance foreshadowed a push that Yamashita especially feared, since Route 4 provided direct access to the deep Cordillera Central. The 105th Division, with defenses across Route 4 at the Rayambugan Farm School, did not have sufficient strength to hold the highway, Yamashita knew.
Recognizing that he could not hope to maintain control along any of the three perimeters he had established in May, Yamashita issued new orders for a strategic withdrawal to a last-stand area. This new perimeter would be set up along the inhospitable valley of the Asin River, positioned between Routes 4 and 11. Accordingly, the orders were as follows: The 105th Division was to retreat from Route 4 to the Pacdan-Antipolo line. The 2nd Tank Division was to move north and hold the line from Tubliao to Antipolo. The 23rd Division was tasked with defending along the Adaoay-Bokod line. The 58th Independent Mixed Brigade was to hold the Agno Valley from Buguias south to Adaoay. The 19th Division was to consolidate the bulk of its forces into the Agno Valley, defending the river line from the Loo Valley south to Buguias. The 79th Brigade was assigned to defend Route 390 at Hapao. Once this last-stand perimeter collapsed, Yamashita planned for all remaining forces to retreat into the barren Asin Valley between Toccucan and Kiangkiang, prepared to fight to the death. The area behind this new last-stand perimeter boasted excellent defensive terrain, and Yamashita estimated that most of his units had sufficient ammunition for machine guns, mortars, and small arms to hold their positions for an extended period. However, the Shobu Group faced dire challenges: they were virtually out of medical supplies, had no clothing stocks, and their food reserves would be completely exhausted by mid-September. If they were not annihilated by the advancing Filipino-American forces, the Shobu Group could only anticipate a slow death by starvation and disease.
Now, it’s time to shift focus from the Philippines and head to Borneo to cover the preparations for the invasion of Balikpapan, codenamed Operation Oboe II. As the 9th Australian Division completed its tasks in North Borneo, General Milford’s 7th Australian Division was assembling at Morotai for the upcoming invasion scheduled for July 1. Milford’s plan entailed an amphibious assault on a two-brigade front between the Klandasan Besar River and Klandasan town, where the Japanese had established their strongest defenses. In June, it was estimated that approximately 3,900 troops were stationed around Balikpapan, composed of: 1,500 in mobile units. 2,400 in anti-aircraft, air force, and base units. Additionally, there were 1,100 Japanese workers, 2,400 Indonesians, and 1,000 Formosans present. Near Samarinda, it was believed there were about 1,500 troops, plus possibly a battalion that had recently arrived from Tarakan. Experience had demonstrated that when estimating the strength of the enemy's resistance, every Japanese and Formosan, whether part of a fighting unit, base unit, or civilian labor group, had to be regarded as a combatant. Key defensive features included: At least 18 coast-defense guns, primarily located on ridges overlooking the sea. 26 heavy dual-purpose guns and 78 medium and light anti-aircraft guns. Offshore, between Klandasan and Manggar, rows of stout poles were driven into the seabed, horizontally braced with timber, and protected with barbed wire. An almost continuous anti-tank ditch, from 12 to 14 feet wide, extended above the beach from Stalkudo to Sepinggang. Extensive trench systems, with many tunnel openings, were detected on the ridges overlooking Klandasan. Numerous concrete strongpoints and a continuous line of bunkers lined the beach’s fringe. This area was among the most strongly fortified that the Australians had encountered during the war. Indeed, Air Vice-Marshal Bostock, responsible for air support of the landing, cautioned the Prime Minister in a letter that these meticulously prepared defenses might result in Australian casualties comparable to those experienced during the landing at Gallipoli. It appeared that the Japanese had established their main defenses on the slopes overlooking the beaches from Klandasan to Stalkudo. The Australian staff believed the Japanese would attempt to contain the invaders within their beachhead area for as long as possible, before withdrawing inland, either south to Bandjermasin or overland to Bintulu in Sarawak. Additionally, it was anticipated that the enemy would direct burning oil onto the beach unless the oil tanks were destroyed during the preliminary bombardment.
Brigadier Ivan Dougherty’s 21st Brigade was to land with one battalion on Green Beach, while Brigadier Frederick Chilton’s 18th Brigade would go ashore with two battalions on the Yellow and Red Beaches. Once a beachhead was secured, the 18th Brigade would seize the high ground dominating the town and clear the harbor for use, while the 21st Brigade would advance along the coast to capture the airstrips. Additionally, Brigadier Kenneth Eather’s 25th Brigade, held in reserve, was set to land on July 2 with the likely objective of thrusting inland along the Milford Highway. Although Admiral Barbey favored a landing site farther east, possibly at Sepinggang, where their ships could be positioned more safely and further from Japanese coastal defense guns, Milford countered with sound reasoning: “Why land up the coast and have to fight miles through jungle, which suits the enemy, when you can go straight in under heavy supporting fire, which the enemy can't withstand, in comparatively open and favorable country?” Supported by General Morshead, this plan received approval, and by June 16, the 7th Division was successfully assembled at Morotai. Admiral Noble’s Task Force 78 would once again transport the Australian troops to the landing area, supported by Rear-Admiral Ralph Riggs’ cruiser group and Rear-Admiral William Sample’s escort carriers.
Against the Japanese defenses, Admiral Kamada’s 22nd Special Base Force consisted of approximately 3,900 troops, with 1,500 in mobile units and 2,400 in anti-aircraft, air force, and base units, in addition to an estimated 4,500 laborers. In preparation for the invasion, aircraft from the Royal Australian Air Force and the 5th and 13th Air Forces began bombarding enemy defenses and storage tanks on June 4. These attacks intensified a week later as they specifically targeted Japanese gun positions. On June 15, Noble’s minesweepers arrived to clear the sea around Balikpapan of magnetic mines, but faced losses, with three ships sunk and three damaged during the operation. Ten days later, American underwater demolition teams began working to locate and breach the underwater obstacles, often under heavy gunfire. To further confuse the enemy, efforts were made to create the impression that the landing would occur at Manggar. This included spreading rumors, landing a reconnaissance party in that area, and demolishing underwater obstacles at both Manggar and Sepinggang. Finally, on June 26, Noble’s convoy set sail from Morotai. After an uneventful voyage, they reached Balikpapan unmolested just before dawn on July 1. During the morning, Riggs’ cruisers and Noble’s destroyers shelled the landing beaches and the defenses behind them, continuing the bombardment until the first waves of landing craft were within 1,300 yards of the shore, at which point the fire shifted to the flanks and rear of the enemy positions. About an hour before the landing, a combined rocket barrage and low-level airstrike were executed, followed by a second rocket barrage just ten minutes before the troops hit the beaches. In total, during the 20 days leading up to the assault, the Balikpapan-Manggar area received 3,000 tons of bombs, 7,361 rockets, 38,052 shells, and 114,000 rounds from automatic weapons, all aimed at crippling the formidable Japanese defenses. Covered by a successful bombardment, the assault waves finally hit the beaches just before 09:00. However, due to navigation errors, the troops were put ashore at the wrong locations. The 2/27th Battalion landed on Yellow Beach instead of Green Beach and quickly captured the Ration, Romilly, Rottnest, and Charlie's Spur positions. The 2/12th Battalion landed on Red Beach instead of Yellow, necessitating a northeast swing to take over Ration and reduce the remaining Japanese defenses in the area. A platoon was also detached to push inland along Vasey Road to seize Portee, while other elements secured Parkes, Plug, and Blyth’s Junction. The 2/10th Battalion, correctly landing on Red Beach, rapidly seized the high ground in front of them. Patrols found Prudent and Petersham Junction to be unoccupied. The 2/10th then assembled at Petersham Junction and captured the lower slopes of Hill 87, successfully taking the hill under assault by noon. Meanwhile, Dougherty landed his reserve units, which also came ashore further west than expected on Yellow Beach. The 2/16th Battalion quickly assembled at Ravenshoe and captured Record, Pigeon, and Mount Malang. By 11 a.m. the battalion was on Ravenshoe, whence Malang and Pigeon were visible. Advancing under sharp fire Captain Madigan's company on the left took Record about 4 p.m., killing 46 Japanese. At 4.5 Captain R. H. Christian's company launched a concerted attack on Malang, sup-ported by the fire of artillery, mortars and machine-guns, and using a flame-thrower. The hill was taken and 40 Japanese were killed. The Australians lost four killed, including the leading platoon commander, Lieutenant Armstrong, and 14 wounded. By nightfall the 2/16th held a line through Malang, Pigeon and Record. It had lost 6 killed or died of wounds in the day and 24 wounded; 86 Japanese dead had been counted.
The 2/14th Battalion advanced swiftly to secure a bridgehead over the Klandasan Besar and seized the Stalkudo ridge. The 2/5th Commando Squadron passed through this bridgehead and attacked northeast but encountered heavy opposition. Returning to Hill 87, the 2/10th Battalion assaulted and captured Parramatta in the afternoon, aided by artillery and tanks, while patrols further secured Newcastle and the Cracking Plant by dusk. A patrol led by Sergeant A. A. Evans was sent out from Davey's platoon towards Newcastle. They silenced a bunker with a flame-thrower, and came to a house from which Japanese were firing. They overcame this position with grenades and small arms fire and then moved on to New-castle. As Evans reached Newcastle he saw the surviving Japanese making off towards Portee. Davey's platoon now occupied Newcastle and the other platoon took up positions on Parramatta. The seizure of Parramatta gave the 2/10th observation over the low ground to the north and the northern end of the town, and tied the battalion in with the 2/12th on Portee; the Japanese were now in a very poor position to counter-attack from the western end of the beach-head. Lieutenant Russack of Sanderson's company led a patrol to the Cracking Plant where it silenced a Japanese pill-box. This patrol was strafed by American aircraft, but worse was to follow. At 4.55 American carrier-borne aircraft made a run over Parramatta from the west and dropped bombs and fired rockets across Hill 87, which had then been in the hands of the 2/10th for four hours and a half. Much of this fire landed in the area into which Captain Brocksopp's" company ("D") had moved and where Daly's command post was established. Three were killed, including Lance-Sergeant Hackett, a veteran of several cam-paigns, and 14 wounded, including Major G. R. Miethke and two other officers. Air panels were displayed in all platoon areas after this. Daly decided to hold that night as far forward as Newcastle, on which he placed two platoons plus a platoon of the 2/1st Machine Gun Bat-talion, all under Captain Bowie. In the day the battalion had lost 13 killed and 30 wounded, but 216 Japanese dead were counted. That night 24 more Japanese were killed while trying to penetrate the Australians' positions and no Australian was hit. All night there were fires round about where houses were burning, and the blazing oil tanks on the Tank Plateau 600 yards to the west of the Parramatta ridge lit up the landscape. Finally, Brigadier Chilton also landed the reserve 2/9th Battalion on Red Beach and sent it west in the afternoon to occupy Klandasan town, leading to the capture of Santosa Hill by nightfall. Thus, the Australians successfully landed at Balikpapan and secured a sizable beachhead, marking the beginning of what would become a fierce and challenging battle.
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In June 1945, American forces, led by Generals Eichelberger and Krueger, fought fiercely against Japanese troops in Luzon, achieving significant victories despite heavy resistance. The tide turned as they captured key positions, restoring hope to Filipinos. Meanwhile, preparations for the Balikpapan invasion intensified. The 7th Australian Division readied for an amphibious assault on July 1 against well-fortified Japanese defenses. Despite facing strong opposition, the Australians successfully landed at various beaches, seizing vital ground.
