- 140 - Pacific War Podcast - Invasions of Guam and Tinian July 23 -30, 1944

Last time we spoke about beginning of the bombing campaign against Japan. The Japanese 11th Army faced setbacks at Hengyang due to resilient Chinese defenses and supply shortages. Reinforced by General Xue Yue, Chinese forces launched effective counterattacks, regaining some territories before being pushed back. By July 20, the Japanese resumed their offensive but faced heavy resistance and were paused. American air raids on Japan and Manchuria intensified under General Arnold’s orders, despite logistical challenges. In Burma, Allied forces under General Stilwell made slow but steady advances, capturing strategic positions and repelling Japanese counterattacks. The Chindits, severely depleted, were eventually evacuated. In Yunnan, Chinese forces encircled and assaulted Japanese positions, achieving significant gains despite heavy resistance and logistical issues. 

This episode is the Invasion of Guam and Tinian

Welcome to the Pacific War Podcast Week by Week, I am your dutiful host Craig Watson. But, before we start I want to also remind you this podcast is only made possible through the efforts of Kings and Generals over at Youtube. Perhaps you want to learn more about world war two? Kings and Generals have an assortment of episodes on world war two and much more  so go give them a look over on Youtube. So please subscribe to Kings and Generals over at Youtube and to continue helping us produce this content please check out www.patreon.com/kingsandgenerals. If you are still hungry for some more history related content, over on my channel, the Pacific War Channel you can find a few videos all the way from the Opium Wars of the 1800’s until the end of the Pacific War in 1945. 

Today our week begins with the ongoings of Operation Forager. By late July, American plans for the invasions of Guam and Tinian were finalized. General Cates’ 4th Marine Division was assigned to land on Tinian’s White Beaches, while General Geiger’s 3rd Amphibious Corps planned two amphibious landings nearly seven miles apart to trap the Japanese in a double envelopment. General Obata, who had relocated his headquarters to Guam, commanded several troops on these islands. On Tinian, Colonel Ogata Keiji's forces included the 50th Regiment, the 1st Battalion of the 135th Regiment, the tank company of the 18th Regiment, and the 56th Naval Guard Unit, totaling 8,039 men. Similar to Saipan, he divided Tinian into three sectors, with most troops defending Tinian Town and Asiga Bay. The 1st Battalion of the 135th Regiment, supported by Ogata’s artillery, formed the Mobile Counterattack Force, ready to respond swiftly to landings. This left only Ogata’s 3rd Company to defend the northwest coast where the Americans planned to land.

Meanwhile, General Takashina’s 29th Division was assigned to Guam and reinforced by Major-General Shigematsu Kiyoshi’s 48th Independent Mixed Brigade and Colonel Kataoka Ichiro’s 10th Independent Mixed Regiment. Takashina’s units fortified the landward neck of the Orote Peninsula and established strong positions on the beaches of Agat, Asan, Tumon, and Agaña Bays. The main fortified area ran along the west coast from Tumon Bay to Facpi Point and included, of course, Orote Peninsula. Other fortified beaches, on the south and east coasts from Merizo to Pago Bay, had been abandoned before W Day, their defenders having moved to the north. Outside the main fortified area, the airfields were provided local defense by anti-aircraft and dual-purpose guns. The most notable and certainly the most effective fortifications on the island were constructed across the neck of Orote Peninsula, which contained a fairly elaborate system of trenches and foxholes arranged in depth, together with large numbers of pillboxes and heavy-caliber weapons. Outside of Orote, the prepared defenses were generally hastily constructed and often incomplete. The typical beach defense was arranged, from the seaward side, in four parallel lines: first were obstacles and mines on the fringing reef offshore; second came beach obstacles and tank traps; third were trenches, machine-gun positions, pillboxes, heavy weapons, artillery, and coast defense guns on the beaches or immediately inland; and, finally, came the machine-guns, heavy weapons, and artillery emplaced on the high ground inland. Insufficient advantage was taken of the high ground, and except on Orote little provision was made for defense in depth. Even as late as the five-week period of pre-invasion bombardment, the Japanese continued to work frantically on improving offshore obstacles and beach defenses, to the neglect of positions in the rear.They also had three tank companies in reserve to strike the beachhead alongside the infantry. Additionally, the 54th Naval Guard Unit, equipped with coastal defense and anti-aircraft guns, secured many positions with reinforced concrete.

The Japanese set up specific defense sectors on this island. Shigematsu’s brigade and Colonel Ohashi Hikoshiro’s 18th Regiment held the Asan Beaches and the Agaña and Tumon Bays. Colonel Suenaga Tsunetaro’s 38th Regiment defended the Agat Beaches, while Kataoka’s forces manned the southern defenses. Additionally, Takashina had a mobile reserve behind the Fonte Plateau, which included five infantry companies, one naval unit, and one tank company. Only Ohashi’s 2nd Battalion was positioned at Guam’s northern end, while Kataoka’s 1st Battalion was deployed to Rota Island. The Americans conducted the longest preliminary air and sea bombardment of the war against Guam, beginning on June 16 after the invasion of Saipan. This bombardment intensified after July 8, when American warships launched the greatest single naval bombardment program of the war, coordinated with Admiral Mitscher’s carrier aircraft. Over the next 13 days, a total of 836 rounds of 16-inch, 5422 of 14-inch, 3862 of 8-inch, 2430 of 6-inch, and 16214 of 5-inch shells were fired at Guam’s main defenses. 

At the invasion of Roi-Namur Admiral Conolly had earned the sobriquet "Close-in Conolly" for his insistence that warships cruise close to shore when firing at land targets. At Guam, he reaffirmed his right to the title, but more important was the systematic procedure he introduced for coordinating naval gunfire and aerial bombardment and checking the results of each. A target board of six officers, representing the air, gunnery, and intelligence sections of the staff, was set up to assign primary missions for air strikes and naval gunfire and assess the damages daily before designating the next day's targets. Aerial photographs were taken each morning and on the basis of these damage was assessed and new targets were assigned. In these operations, the admiral's staff was aided by the presence aboard Appalachian of General Geiger who, as commanding general of the landing force, naturally had the greatest personal concern about the accuracy both of the bombardment and of the damage reports submitted afterward.

In the final three days before the landing, Mitscher’s planes conducted 1430 bombing sorties and 614 strafing attacks, dropping a total of 1131 tons of bombs, depth charges, and rockets, while losing only 16 aircraft. Despite the extensive bombardment, positions reinforced with coral and concrete remained in good condition. Anti-aircraft artillery and harbor installations suffered minimal damage, power installations in caves were unharmed, and communications were not interrupted.

The intensity of the attacks on the western defenses suggested a likely amphibious landing there, prompting Takashina to abandon the ineffective southern and northern defenses. Meanwhile, Conolly's vessels, carrying Geiger's Southern Landing Forces, departed Eniwetok for Guam between July 11 and 18, arriving successfully by July 21. Between July 14 and 17, three underwater demolition teams scouted the landing beaches, and under the protection of LCI gunboats, they removed 640 obstacles from the Northern Beaches and 300 from the Southern Beaches. On the morning of July 21, in excellent weather conditions, the Americans began a preliminary bombardment. Admirals Conolly and Reifsneider directed the shelling of Asan and Agat beaches, respectively, while Admiral Mitscher’s carrier aircraft bombed and strafed the fourteen miles of coastline from Agaña to Bangi Point. At 07:40, the assault waves crossed their departure lines under the cover of rocket fire from LCI gunboats. Eight minutes before landing, when the vehicles were 1200 yards from shore, Conolly's warships launched a final massive bombardment, and Mitscher’s fighters provided covering strafing attacks. These attacks were to be shifted inland as the troops approached the shore. Despite the intense bombardment from ships and aircraft, the Japanese managed to target the assault waves, destroying nine amtracs from the 3rd Marine Division. Nevertheless, the waves of vehicles advanced, and at 08:28, the first LVTs landed, two minutes ahead of schedule. Further south, shore fire was even heavier, hitting one LCI gunboat and destroying 13 amtracs. However, the landing formation held, and the troops landed on schedule.

Despite numerous concrete pillboxes still manned by the Japanese, both assault regiments advanced rapidly. Colonel Merlin Schneider’s 22nd Marines successfully captured Agat amid strong resistance but were eventually halted at a hill position northwest of the town. Meanwhile, Lieutenant-Colonel Alan Shapley’s 4th Marines cleared Bangi Point and Hill 40, setting up a roadblock supported by five tanks on Harmon Road. By the end of the day, General Shepherd had established a beachhead approximately 1300 to 2300 yards deep, at the cost of around 350 casualties and 24 lost LVTs.

At 08:30, the infantrymen of Lt. Col. Robert D. Adair’s 2nd Battalion were climbing down cargo nets from their transports into the bobbing landing craft that were to carry them to the edge of the reef. By 10:30 all boats were in position near the line of departure waiting for the signal to go in. For three and a half hours they circled impatiently. At last, at 14:05, came the message to proceed to the beach and assemble in an area 300 yards inland from Gaan Point. Unfortunately, no amphibian tractors were on hand to transport Adair's men over the reef and onto the shore line, and of course their LCVPs were too deep-drafted to negotiate either the reef or the shallow waters inland of it. Over the sides of their boats the men climbed, and waded the rest of the way in water at least waist deep. Some lucky few were able to pick up rides in Marine LVTs on the landward side of the reef, but most stumbled in over the rough coral bottom, cutting their shoes en route and occasionally falling into deep potholes. Luckily, no enemy fire impeded their progress, and except for the dousing they got and the exhaustion they suffered the troops of the 2nd Battalion, 305th Regiment completed their ship-to-shore movement without injury.To the north, Colonel Edward Craig’s 9th Marines advanced steadily against fairly heavy machine-gun and rifle fire, securing a beachhead about 1500 yards deep. Colonel Arthur Butler's 21st Marines, facing only moderate opposition but difficult terrain, cleared Asan Town and gained a foothold on the face of the Fonte Plateau.

On the left flank, Colonel William Hall’s 3rd Marines encountered the heaviest resistance from two complex cave defense systems on Chonito Cliff and Bundschu Ridge. Hall’s men cleared Chonito Cliff and Adelup Point after several costly assaults and heavy casualties, but progress against Bundschu Ridge was limited, resulting in a 200-yard-wide gap between the 3rd and 21st Marines. Nevertheless, General Turnage secured a beachhead approximately 1600 by 4000 yards and had landed all division infantry, artillery, and support units, at the cost of 105 killed, 536 wounded, and 56 missing.

Upon receiving the alert of enemy landings, Takashina promptly mobilized his reserve units to the Fonte Plateau in an attempt to contain Turnage’s Marines within their limited beachhead. Throughout the night, he initiated several fragmented counterattacks, all of which were easily thwarted, resulting in significant Japanese casualties. In the southern sector, the 4th and 22nd Marines heroically fended off numerous well-coordinated counterattacks, managing to destroy four enemy tanks and eliminate Colonel Suenaga along with his 38th Regiment. By July 22, Geiger’s forces began to expand their footholds on the beaches. In the northern front, Hall’s assault on the Bundschu Ridge faced formidable resistance. Despite some Marines reaching the ridge with support from 20mm and 40mm fire, they were compelled to withdraw due to intense mortar shelling. Unbeknownst to them, their relentless attack forced the Japanese to abandon the position, albeit at a significant cost to the 3rd Marines, which suffered up to 615 casualties and was unable to sustain the advance. Meanwhile, Butler’s 21st Marines encountered difficulty clearing the ravine separating them from the 3rd Marines, necessitating the deployment of their reserve 1st Battalion to support the depleted 2nd Battalion. On the right flank, Craig’s 9th Marines encountered minimal resistance as they swiftly secured the Piti Navy Yard, followed by the landing of the 3rd Battalion on Cabras Island after extensive naval and aerial bombardment. The only significant engagement during the night was a Japanese bayonet charge backed by mortar fire, which Butler’s 1st Battalion successfully repelled, inflicting heavy losses on the enemy.

To the south, following the night landings, the 305th Regiment underwent reorganization while Tanzola's 2nd Battalion relieved Shapley’s 2nd Battalion. Schneider’s 22nd Marines encountered moderate resistance as they moved northward after crossing the Ajuya River. Despite lacking tank support, they advanced until halting approximately 250 yards north of RJ 5. Simultaneously, Shapley’s 4th Marines launched an assault towards Mount Alifan's steep slopes, successfully neutralizing entrenched enemy positions using demolitions and grenades, though hindered by rugged terrain. Eventually, a platoon reached the summit, finding no enemy presence. Tanzola’s 1st and 3rd Battalions then advanced along Harmon Road towards the Maanot Pass, navigating eroded hills and dense vegetation to secure the O-a high ground line. 

The 306th Infantry Regiment's landing on the White Beaches required the entire day because of communications problems and landing craft shortages. It was not until the next day that the 4th Marines was fully replaced by the 306th. 3rd Amphibious Corps Artillery was landing over White 1 at this same time, as was the 77th Division Artillery, leading to a great deal of congestion, especially when coupled with the landing of smaller units, supplies, and ammunition. Most artillery battalions were in-place by nightfall as was the 9th Defense Battalion deployed along the beaches. The defense battalions, besides providing air defense and direct fire support on ground targets, were positioned to engage any Japanese counter-landing attempts on the beachhead. The 77th Division, with the 305th on the right (center of the beachhead) and the 306th on the left, would secure the southern portion allowing the 4th Marines to move north with the 22nd Marines to seal off the neck of Orote Peninsula.

They continued their advance beyond Harmon Road and Maanot Pass, securing commanding positions overlooking Orote Peninsula. Meanwhile, Schneider’s 22nd Marines, initially advancing rapidly against scattered resistance, encountered intense enfilade fire from hills surrounded by rice paddies while attempting to maneuver across the neck of Orote Peninsula. This compelled them to withdraw approximately 400 yards to a line of hills south of Old Agat Road.

Further to the north, Hall’s 3rd Marines eventually discovered that the Bundschu Ridge had been deserted. However, following their clean-up operations, they were not in a condition to advance any further. Craig’s 3rd Battalion successfully secured Cabras Island and then relieved the 2nd Battalion on the mainland. Meanwhile, Butler’s 21st Marines faced challenges in bridging the gap with the 3rd Marines and encountered limited progress against well-fortified enemy pillboxes on the plateau’s slopes. Turnage initiated the first contact attempt with Shepherd’s brigade on July 24th, but the 30-man patrol was forced to retreat due to enemy fire. Despite Butler’s 2nd Battalion's efforts to close the gap by attacking up the ravine, they were repeatedly hindered by heavy machine-gun fire from caves on the cliff sides. Although both the 3rd and 9th Marines managed to enhance their positions, Turnage's casualties rose to 2034 since the initial landing.

Further south, Shepherd, in response to the formidable defense on the neck of the Orote Peninsula, instructed Schneider to advance the 1st and 3rd Battalions in company columns along the Agat-Sumay Road. The objective was to penetrate the enemy lines and seize the O-2 Line from the coast to Apra Harbor, while the 2nd Battalion shifted to occupy strategic high ground near Atantano from its position on the Old Agat Road. This maneuver not only flanked the Japanese strongholds guarding the rice paddies but also established a barrier across the neck of Orote, securing the beachhead line in front of the brigade.

Following an extensive air, artillery, and naval bombardment, Schneider's primary thrust along the Agat-Sumay Road encountered determined resistance but successfully advanced to the R-2 Line. The 1st Battalion then spread out to the right, while the 3rd Battalion veered further east across the hills, swiftly capturing the fortified positions around the rice paddies that had posed significant challenges the previous day. By nightfall, the 1st Battalion had reached the O-2 Line, but the 3rd Battalion halted 400 yards short of its target, prompting Shapley's 2nd Battalion to fill the breach between them. After repulsing a vigorous counterattack, the 2nd Battalion pushed forward with minimal opposition and secured Atantano. Consequently, by the end of July 24, Shepherd had firmly established his beachhead and contained the enemy on the Orote Peninsula, albeit with casualties totaling 200 killed, 748 wounded, and 97 missing. General Bruce, with the remainder of the 77th Division, assumed control of most of the beachhead perimeter, while Shepherd's Marines readied for the capture of Orote. Subsequently, after repelling several tank-led counterattacks resulting in the destruction of 12 Japanese tanks, they sealed off the peninsula entirely on July 25. By afternoon, approximately 2500 troops under Commander Tamai Asaichi were confined to the eight square miles of Orote Peninsula. Meanwhile, Turnage pressed his forces to secure the objective beachhead definitively.

Accordingly, the 9th Marines progressed southward along the Apra Harbor shoreline towards the Aguada River, reaching the midpoint before being compelled to retreat to the Laguas River due to Craig's stretched lines. Meanwhile, the 21st Marines faced formidable defenses at the Mount Chachao-Aluton-Tenjo complex, managing to establish defensive positions just shy of Mount Tenjo Road after slow progress. Simultaneously, the beleaguered 3rd Marines, with reinforcements from Craig's 2nd Battalion, launched a determined assault, overcoming moderate resistance and mortar fire to seize Mount Tenjo Road and gain a vantage point. Despite the extended frontline, troops stationed on the newly captured high ground could finally survey the terrain ahead by nightfall.

As Takashina consolidated his forces on the plateau, he prepared for a coordinated counterattack aimed at dividing and conquering the enemy. The 48th Independent Mixed Brigade planned to strike Turnage's left flank before pivoting northeast to target Hall's rear. Meanwhile, the 18th Regiment aimed to assault Butler's positions and advance toward the coast to establish a new defensive line, targeting the enemy's headquarters, artillery, and supply units. Additionally, elements of the 10th Independent Mixed Regiment were tasked with exploiting an 800-yard gap between the 9th and 21st Marines, protected only by the 3rd Reconnaissance Company.

In a desperate move following a failed attempt to evacuate by barge, Tamai opted for a nighttime banzai charge with his trapped 2500-strong force, seeking to break free from the Orote Peninsula and join Takashina's troops at Fonte. After dusk, the intermittent showers that had been falling all day became more frequent. A heavy downpour hampered organization of the brigade's defense for the night. On the other hand, the pitch blackness and the unpleasant weather aided the Japanese in making preparations for their supreme effort. Marines in the front lines could hear screaming, yelling, laughter, and the breaking of bottles as the Japanese made final arrangements. At times so much clamor could be heard that reports reached the command post that the assault had started. Afterwards someone aptly said that the confusion "sounded like New Year's Eve in the Zoo." While the enemy made ready and drank, Marine artillerymen laid down normal barrages along the swamp's edge and at all other points of possible penetration. Shortly before midnight the Japanese commanders felt that their men had reached the proper emotional state, and the assault began. Sake-crazed attackers swarmed from the cover of the mangroves in front of the 3rd Battalion, 22nd Marines. Led by flag-waving, sword-swinging officers, the enlisted men stumbled forward, carrying everything conceivable. Unsteady hands clutched pitchforks, sticks, ballbats, and pieces of broken bottles, together with the normal infantry weapons. The assault faced formidable resistance from Marine forces, particularly Shapley’s 1st Battalion, which alone accounted for 256 enemy casualties. 

When the surging Japanese mass came within range, Marine forward observers and company commanders gave the order to commence firing. Brigade, 77th Division, and corps artillery, 37mm guns, 81mm and 60mm mortars, machine guns, rifles, and grenades saturated the entire area. At one time officers brought the fire of the Pack Howitzer Battalion, 22d Marines, to within 35 yards of 3/22's front lines in an at tempt to stop the swarming horde. One weapons company lieutenant reported: "Arms and legs flew like snowflakes. Japs ran amuck. They screamed in terror until they died." But in a powerful attack it is inevitable that some men will seep through the blocking fire. Company L, 3/22, received the brunt of the subsiding attack and repulsed it before too much damage could be done. Those Japanese who survived fled to the momentary safety of the swamp. But observers shifted the artillery fire and between midnight and 0200 some 26,000 shells took a heavy toll of the remaining peninsular defenders. On the right flank of the 22d Marines a second counterattack hit. The Island War describes the action quite vividly: “. . . At its height, flares revealed an out-of-this-world picture of Nipponese drunks reeling about in our forward positions, falling into foxholes, tossing aimless grenades here and there, yelling such English phrases as they had managed to pick up, and laughing crazily, to be exterminated in savage close-in fighting. Succeeding waves were caught in a deadly cross-fire. Not until dawn did this attack finally dwindle out, at which time more than four hundred bodies were counted in front of the position.” In contrast to the frenzied close quarter action in the 3/22 zone, the platoon from Company A (1/4) that filled the gap between the two regiments participated in a shooting gallery affair with the Japanese. Enemy troops made no attempt at a concerted attack, and the platoon plus artillery, without the loss of a single Marine, killed 256 Imperial soldiers. This fantastic figure was verified by officers from regiment the following morning.

Despite the intense machine-gun and artillery fire, some Japanese managed to infiltrate Marine positions, engaging in fierce hand-to-hand combat. However, by dawn, the Japanese offensive had been halted, with most remaining enemy forces eliminated, leaving Tamai with no option but to defend Orote Peninsula to the end. Meanwhile, Takashina's main assault, launched on July 26 at 04:00, faced initial success in overrunning Company B positions but was ultimately contained by the relentless machine-gun fire of the 1st Battalion. 

Major Maruyama's men (2/18) advanced noisily, shouting, "Wake up American and die." The initial impetus of the assault passed completely over Company B in the center, previously reduced to about 50 men, and streamed through the gap down a draw toward the cliff. Despite the breakthrough, companies held the shoulders of the penetration and Lieutenant Colonel Williams ordered the units to refuse their flanks to the cliff. Company A on the left, commanded by Captain William G. Shoemaker, rallied in the face of the withering fire and overwhelming numbers. Shoemaker pulled back his right platoon to deny his flank to the enemy and to permit regrouping for a local counterattack. Company C (Captain Henry M. Helgren, Jr.) also successfully refused its flank to protect the position and immediately began firing into the onrushing Japanese. Tanks parked in the rear of the Marine positions took a great toll as the intruders surged through the widening gap. One report described the rush on the tanks as resembling a horde of ants. It went on to say of the Nipponese: “Savagely they swarmed upon the mechanized vehicles, oblivious of the vicious machine-gun fire, and frantically pounded, kicked, and beat against the turrets in an attempt to get the crew within. When this seemed futile they leaped to the ground and continued their wild rush down the draw to the rear areas. . .” Demolition charges were forgotten in the mad scramble to reach deeper into Marine-held territory. Machine gunners of 1/21 had a field day. Never had they seen such lucrative targets, but grenades and bayonets soon silenced the Marines as enemy soldiers overran the gun positions. Many of the Japanese were killed as they moved through the lines and into the ravine.

Although some of the infiltrating Japanese got down the cliff to attack the battalion command post and Butler’s mortar platoons, killing most of the mortarmen before being repelled by service troops, To the left, Craig’s tenacious 2nd Battalion, in its exposed position, received the brunt of Shigematsu’s attack, yet it managed to defeat seven determined counterattacks without losing any ground. Nonetheless, though they killed 950 Japanese, they suffered 50% casualties as well. Looking right, Ohashi’s 3rd Battalion hit Butler’s 3rd; and although two machine-guns were initially captured, their attack ended up being rapidly repelled. Consequently, the Japanese slid along the front and attacked down the vulnerable 800-yard gap, successfully defeating a strong roadblock to set up a dangerous line on the high ground behind Butler’s 3rd Battalion. 

The lack of a swiftly organized regimental reserve line led to approximately 70 Japanese infiltrating into the Division Hospital area, where they were eventually repelled by a pioneer force. The first warning came about 6:30 when corpsmen reported that a number of enemy soldiers could be seen on the high ground to the right of the hospital. Division headquarters immediately ordered Lieutenant Colonel George O. Van Orden (Division Infantry Training Officer) to take command of two companies of pioneers standing by for just such an eventuality and clear the enemy from the hard-pressed area. At the hospital, doctors ordered patients to evacuate the tents and go to the beach. Onlookers saw a pathetic sight as half-clothed, bandaged men hobbled down the coast road helping the more seriously wounded to safety. 41 of the patients grabbed rifles, carbines, hand grenades, and whatever else they could find and joined the battle. The hospital doctors, corpsmen, and pajama-clad patients presented a rare sight as they formed a defensive line around the tents. It was a solid line, however, and one that held until the recently organized reinforcements arrived. Only one patient was wounded during the fighting, but one medical officer and one corpsman later died of wounds. The casualty list also included one medical officer, one dental officer, one Navy warrant officer, 12 corpsmen, and 16 Marines from the medical companies wounded in action. This does not include those casualties suffered by Van Orden's force. After cleaning out the assigned area, Van Orden proceeded up the Nidual River Valley in pursuit of the fleeing Japanese. The attack had pushed the enemy back to the hill at the head of the ravine by 11:00, but a request to send a Marine patrol to the ridge to determine the hostile strength was denied. Other plans had already been made for the assault of this dominating terrain. It was from this high ground that Major Yukioka's men paralyzed the operation of 3/21's CP and threatened the flank of both the 9th and 21st Marines.

While this action was taking place, the 12th Marines CP and several of its battalions were engaged in stopping the suicide squad attacks. In order to have these parties in position to make their foray in conjunction with the all-out offensive, enemy commanders had ordered the groups to infiltrate behind Marine lines on the night of 24-25 July. With typical Japanese patience, the raiders lay hidden in caves all day. As soon as darkness came on the night of 25-26 July they started firing random shots into the headquarters of the 12th Marines and began to move in small groups down the Asan Valley. A hand grenade duel went on during the early hours of darkness, but some of the intruders sought the safer confines of a cave not 20 feet from the headquarter's fire direction center. The artillerymen's perimeter defense held, and only one of the enemy succeeded in getting through to the guns. He was killed in the 3d Battalion's area before he could do any damage. In the five-hour long fighting around the regimental headquarters, 17 explosive-laden Japanese died. Most of them carried packs containing about 20 pounds of TNT with ready detonators, while others carried magnetic mines. With the coming of daylight, patrols went out to clean up any troops that might cause trouble later in the day. Men of the 12th Marines killed approximately 50-60 more enemy soldiers and drove the remainder into other areas where they were liquidated one by one.

Despite the initial success of Takashina’s well-coordinated counterattack, by noon, his forces had suffered defeat, marking the breaking of the backbone of Japanese resistance on Guam. Marine casualties were significant, with around 166 killed, 645 wounded, and 34 missing between July 25 and 27. Consequently, the 9th Marines retreated approximately 1500 yards to establish better defensive positions, and a battalion of Colonel Stephen Hamilton’s 307th Regiment was deployed near Piti Navy Yard. However, the focus now shifted to covering the invasion of Tinian. While naval guns had intermittently harassed Tinian since June 11, the preliminary bombardment of Saipan’s sister island commenced on June 20, with the first Army artillery battery targeting northern Tinian. By July 9, the 531st Field Artillery Battalion had fired a total of 7571 rounds. Following the fall of Saipan, the remaining 24th Corps Artillery and Marine howitzers intensified the bombardment, maintaining a continuous round-the-clock schedule and expending a total of 24,536 rounds on northern Tinian.

For the most part, 14th Corps Artillery confined its efforts to the area north of the line between Gurguan Point and Masalog Point, while aircraft restricted their efforts to the southern half of the island. Naval ships were assigned any targets on Tinian deemed unsuitable to either of the other two arms. Coordination of the three supporting arms was assigned to the corps artillery representative attached to General Schmidt's staff. In one instance, an artillery air observer discovered three 140-mm. coastal defense guns on Masalog Point that were within easy firing range of White Beaches 1 and 2, but were masked from field artillery. The battleship Colorado was called in and, with its main batteries adjusted by an airborne artillery observer, succeeded in neutralizing or destroying the enemy weapons. Because the spotting plane was not in direct radio contact with the ship, it was necessary for the plane to submit its spotting data to the artillery post by radio, whence they were relayed by telephone to General Schmidt's headquarters, and in turn by radio on another frequency to the firing ship. In spite of this somewhat complicated system of communications, the time lag was so slight as to be insignificant.

Meanwhile, starting from June 22, the P-47s belonging to the 318th Fighter Group maintained a relentless barrage on the airfields at Ushi, Gurguan Point, and just east of Tinian Town through constant strafing and bombing, further devastating the town to ruins. Beginning on July 15, naval gunfire operations were reinstated, with Admiral Hill’s cruisers and destroyers delivering destructive bombardment daily against Tinian’s harbor defenses. Then, on July 22, two P-47s dropped the first napalm bombs used in the Pacific war on Tinian, proving highly effective in incinerating canefields, underbrush, and enemy personnel located in open trenches and dugouts. The following day, Hill intensified preparatory fire with a formidable naval force comprising three battleships, two heavy cruisers, three light cruisers, and sixteen destroyers, positioned strategically to shell Tinian from all directions. However, there was no attempt to focus on the White Beaches to mislead the Japanese about the actual landing point. Throughout the rainy night, destroyers and cruisers maintained control over crucial road junctions while an UDT conducted a last-minute underwater reconnaissance, albeit unsuccessfully attempting to detonate recently discovered mines due to adverse weather conditions. At dawn on July 24, Hill’s transports carrying the 2nd and 4th Marine Divisions finally departed from Tanapag Harbor for the short journey to Tinian, successfully reaching their designated areas by 06:00. Simultaneously, the onslaught of artillery, air raids, and naval bombardment persisted over the Japanese defenses, intensifying into a full-scale onslaught by 07:00, with particular focus on the White Beaches. Additionally, efforts were made to neutralize mines on White 2, although these attempts proved futile.

As the assault waves took shape, General Watson’s Marines effectively executed the demonstration near Tinian Town without suffering any casualties. This demonstration effectively held the defenders in place, preventing them from deploying northward. However, a cleverly concealed Japanese battery managed to inflict significant damage on the battleship Colorado and the destroyer Norman Scott, resulting in the loss of 62 lives and 245 wounded before being neutralized. At 07:17, the initial landing wave crossed the designated line and began the 3000-yard journey to the beach, supported by intense pre-landing bombardment and rocket fire from LCI gunboats. 

At about the same moment small-caliber fire--estimated variously as 50-caliber, 20mm and 40mm--began falling around the LST's. Its source could not be located because of the pall of smoke and dust that cloaked the island. Regarding this incident the logistics officer of the 2d Battalion, 23d Marines, aboard one of the LST's in the area, recalled: “The fire . . . wounded two or more Navy enlisted men of the crew of the vessel, and possibly a couple of Marines belonging to the landing team. . . . My recollection concerning the Marines who were wounded is hazy . . . the incident created a stir and speculation concerning the source of the fire, but everyone soon settled down to the business at hand.” Despite encountering the sporadic small-caliber fire, the LVTs successfully reached the narrow beaches by 07:50. Upon landing, Company E of the 24th Marines swiftly engaged and eliminated a small beach-defense unit on White 1, while the remainder of the battalion made landfall. On White 2, the 2nd and 3rd Battalions of the 25th Marines landed simultaneously but faced a delay in advancing due to the need for engineers to clear 100 horned mines that had destroyed three LVTs. Subsequently, Colonel Batchelder’s Companies G and I circumvented two enemy blockhouses and initiated an inland attack, while other units subdued strongpoints. However, the presence of additional mines and staunch resistance from caves and ravines prevented them from reaching their objective at the O-1 Line and Mount Maga. Meanwhile, Colonel Hart’s 1st and 2nd Battalions of the 24th Marines successfully advanced to the O-1 Line amid minimal opposition. Later in the day, reserve and artillery battalions were landed, along with Colonel Jones’ 23rd Marines, although their landing was delayed due to communication issues. This delay proved beneficial due to heavy congestion on White 2 at the time.

By nightfall, Colonel Wallace’s 1st Battalion, along with the 2nd and 4th Tank Battalions, under Hill's command, successfully disembarked 15614 men ashore. General Cates, anticipating Japanese counterattacks, directed his troops to halt at 16:30 to fortify defenses, achieving a beachhead spanning about 7000 yards. This came at a cost of 15 Marines killed and 225 wounded. Ogata, as expected by Cates, immediately ordered counterattacks with the 1st and 2nd Battalions of the 50th Regiment and mobilized the Mobile Counterattack Force. While Japanese probes commenced at 22:30, the major assaults, marked by fierce banzai charges, began after midnight. 

The attack on the left came first and lasted longest. At 2:00, men of the 1st Battalion, 24th Marines, straining their eyes through the black moonless night, suddenly saw a compact group of Japanese a short 100 yards away. The Marines opened fire. The compact group became a screaming mass of attackers as the first Marine bullets and shells found targets. Now the shadows were alive with about 600 leaping Japanese naval troops, loaded with aggressive spirit, requiring no instructions to make their screaming charge. Marines called flares into action; the battlefield became light. Marines needed no orders either: the 37mm guns sprayed canister; machine guns cut into the enemy area with grazing fire; rifles pounded out at sighted or suspected targets; mortars crunched into the defilade areas; artillery crashed steadily behind the Japanese to shatter and destroy any reinforcement group. The tightly packed foe was a choice target for all these weapons, and hundreds of shells lashed his ranks. At no time did the enemy penetrate the 1st Battalion; but extremely heavy pressure against Company A, the unit that bore the brunt, caused the battalion commander to reinforce it with engineers, corpsmen, communicators, naval gunfire liaison and shore party personnel. The fight continued hot and heavy until about 0545, when dawn and the vigor of the enemy effort broke simultaneously. Medium tanks from Company B, 4th Tank Battalion, entered the fray at this time and stopped all further thrusts at the Marines' lines. Many Japanese, convinced that all was lost, committed suicide with grenades. While armored amphibians afloat fired on enemy groups hiding along the coast, Marines of the 1st Battalion, 24th Marines, mopped up the area to their front, an activity completed by 0700. They counted 476 Japanese bodies, most of them within 100 yards of Company A's lines. Although no figures are available for Marine casualties in this action, the battalion commander estimated that ". . . Company A was reduced to about 30 men with usable weapons before the enemy was repulsed."

Ogata’s infantrymen struck Cates’ center thirty minutes later, yet their efforts were thwarted by intense small-arms, mortar, and 37mm fire. Despite briefly breaching the line through weak points, they were ultimately defeated by rear elements after prolonged and heavy fighting. 

This time, though many of the attackers fell forward of the lines, others penetrated a weak spot at the boundary between the two Marine regiments. About 200 Japanese poured through this spot before the flow could be stopped. After pausing in a swamp behind the lines, the enemy force speared out in two prongs: one straight into the beachhead toward U. S. artillery positions, the other turning west into the 25th Marines' rear areas. The latter group of Japanese attained first contact when they met a well-prepared support platoon from the 3d Battalion, 25th Marines. Positioned to contain just such a penetration as had occurred, the Marines quickly eliminated this Japanese threat, killing 91 in a brief, violent skirmish. The other prong pushed deep into the rear of the beachhead, finally reached the 75mm howitzer firing positions of the 2d Battalion, 14th Marines. Battery D, firing a mission for the 24th Marines, suddenly found itself beset from the front by many determined Japanese. Marines not actively engaged in servicing the howitzers rallied to the defense of their positions with small arms, while the remainder continued firing an artillery mission for the 24th Regiment. Later, as pressure mounted, all hands turned to the task of stopping the Japanese close at hand. At this juncture the .50-caliber machine guns of the other two batteries (E and F) of the battalion levelled a heavy volume of enfilading fire into the area forward of besieged Battery D. This fire, in the words of the battalion executive officer, "literally tore the Japanese . . . to pieces." To reinforce Battery D in its bitter fight, Company C, 8th Marines, arrived at 0445. But by then the situation was well in hand; the Japanese had faltered and stopped before the deluge of small-arms fire. Morning revealed about 100 dead Japanese in the area, while the artillerymen had lost but two of their number--both killed manning a .50-caliber machine gun with Battery D. The only Japanese penetration of the night had shattered itself against a prepared rear area. Up at the front, meanwhile, Marines of the 25th Regiment and the right (2d) battalion of the 24th Regiment, fought off a series of frontal rushes upon their positions. In each case the Japanese were stopped at the barbed wire forward of the Marines' lines. The all-night firing had taken a heavy toll of the Marines' ammunition stocks, however, and by shortly before daylight there was concern along the lines that another heavy attack might exhaust supplies. Dawn came first. Attached tanks moved up at once to range the area forward of the lines. They blasted points of resistance with their 75mm guns, killing or chasing such few Japanese as had survived the night melee. Nearly 500 Japanese were killed in the attacks against the center of the beachhead and in the skirmishes behind the lines following the penetration.

The third and last major enemy effort struck the extreme right (south) flank of the beachhead at 3:30. The 2d Battalion, 23d Marines, in position along the coast, bore the brunt of this thrust, although the 2d Battalion, 25th Marines, also figured prominently in the action. Moving north along the coastal road, the enemy force consisted of five or six light tanks (about half of those available to the Japanese at Tinian) with infantrymen riding and following on foot. First warning of the enemy move came when Marine listening posts stationed along the road a short distance forward of the lines reported enemy tanks rumbling in from the south. With the tanks an estimated 400 yards in front of the lines, Marine artillery opened up. The tanks came on. Ready for just this situation, U. S. ships began firing illuminating shells over the area, virtually turning night into day. Bazookas, 75mm half-tracks, and 37mm guns attached to three battalions now went into action. One of the 37mm platoons, positioned astride the coral road, leveled point-blank fires into the enemy armor. Even so, one fast-moving tank weathered a 37mm hit and drove through the front lines into rear areas before a Marine bazookaman finished it off. An officer present on the scene described the action as he saw it: “The three lead tanks broke through our wall of fire. One began to glow blood-red, turned crazily on its tracks, and careened into a ditch. A second, mortally wounded, turned its machine guns on its tormentors, firing into the ditches in a last desperate effort to fight its way free. One hundred yards more and it stopped dead in its tracks. The third tried frantically to turn and then retreat, but our men closed in, literally blasting it apart. . . . Bazookas knocked out the fourth tank with a direct hit which killed the driver. The rest of the crew piled out of the turret, screaming. The fifth tank, completely surrounded, attempted to flee. Bazookas made short work of it. Another hit set it afire, and its crew was cremated.” Thus, five tanks stood immobile on the field of battle. If a sixth accompanied this incursion, it escaped, since there was no trace of it the following morning when Marines moved through the area. Despite the fact that their armor was gone, enemy foot soldiers from the 1st and 2d Battalions, 50th Infantry, and the 1st Battalion, 135th Infantry, pressed toward the Marines. The fighting that ensued was close-in and savage, but the Japanese never cracked the tight defense. The few who seeped through the lines met a quick end at the hands of the 23d Marines' reserve (1st Battalion), positioned to provide depth in this precise area. The operations officer of the 2d Battalion, 23d Marines, described the weird termination of the Japanese activities: “. . . as it began to get light, Jap bodies began to fly ten to fifteen feet in the air in the area in front of our lines. . . . We knew that hand grenades did not have the power to blow a man's body that high and could not figure out what was happening. [Later] we moved out to mop up. . . . It turned out that about fifty percent of the dead Japs carried magnetic mines and had obviously been ordered to break through our lines and destroy the tanks in the rear of us. . . . The Japs who were wounded and unable to flee were placing the tank mines under their bodies and tapping the detonators.” Daylight revealed that the enemy had expended 267 men and five tanks (of 12 on the island) against the right flank of the beachhead with no success. By the end of the night's counterattacks, 1241 Japanese bodies lay scattered along Cates’ front, with the 1st Battalion, 135th Regiment virtually decimated, while Marine casualties numbered less than 100. Reflecting on the engagement, they later concluded: "It was there and then that [we] broke the Jap's back in the battle for Tinian". This assessment proved accurate, as Ogata’s forces began retreating towards the southern end of the island.

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Similar to the experience invading Saipan, Guam and Tinian proved to be literal horror shows. The savagery of the Island hoping campaign had increased ten-fold. The Japanese hoped by inflicted as much pain as possible, the Americans might simply come to the peace table, but was there any real chance of that?