The 'Battle of Peleliu', which was codenamed 'Stalemate II', was fought for the island of Peleliu between US and Japan forces during the 'Forager' campaign for the Mariana and Palau island groups (15 September/27 November 1944).

Major General Julian C. Smith’s III Amphibious Corps (in the form of the 1^st Marine Division and then the US Army’s 81^st Division), fought to capture an airfield on the small coral island of Peleliu within the context of the larger 'Forager' campaign between June to November 1944 in the Pacific theatre.

The main objective of the Palau islands assault, Peleliu lies on the south-western end of the Palau barrier reef, and Angaur, the other objective, is 7 miles (11.25 km) to the south-west while Eil Malk, the nearest large island, is 8 miles (12.9 km) to the north-east and Babelthuap is 25 miles (40 km) in the same direction. Often described as possessing the shape of a lobster claw, Peleliu is about 6 miles (9.7 km) long on its north-east/south-west axis and slightly more than 2 miles (3.2 km) across. The island’s main part is elongated, but a sprawling peninsula, almost an island in itself, is attached to the south-eastern side by an isthmus just 300 yards (275 m) wide. Most of the island’s coast is lined with mangrove swamps. Much of the southern one-third of the island, its widest portion, is generally flat, but covered by dense scrub woods and scattered palms, as also is the south-eastern peninsula. On this area lay the well-developed X-shaped Japanese airfield and a road system. The island’s north-eastern two-thirds is an arm 3,500 yards (3200 m) long and averaging 1,000 yards (915 m) wide. This is covered by an extremely rugged spine of rocky ridges, coral outcroppings, rubbled valleys, gorges, crags and sinkholes pockmarked with caves, and all heavily wooded with dense underbrush. The eastern side of the arm’s coast is lined with mangrove swamps. Many of the features in this jumbled terrain would receive nicknames from the marines and soldiers who fought on them. Western and eastern roads extended along both sides of the coast on the arm to its north-eastern end, Akaraoro Point. Here there was a phosphate refinery to process the mineral mined on the island. The southern half of the arm is dominated by the 550-ft (168-m) Umurbrogol mountain, and the central portion is covered by the slightly lower Kamilianlul mountain. Umurbrogol is faced with 30- to 60-ft (9.1- to 18.3-m) cliffs on its northern side and edged by a mangrove swamp on its southern side. On the north-eastern end of the arm is the T-shaped Amiangal mountain. These 'mountains' are actually rocky ridges, and in 1944 were a formidable obstacle to the attackers and were thus ideally suited for the needs of the defenders. Well-dug-in pillboxes and fortified cave positions were developed in depth with interlocking fields of fire providing mutual support. The natural defences were reinforced by elaborate tunnel systems, of which the most intricate was those built by the Imperial Japanese navy on the northern arm.

Off Peleliu’s southern tip is Ngarmoked island, which was in fact connected with the main island by a narrow isthmus and also known as the Southwest Promentory. A similar, though smaller, feature was the Southeast Prementoru, which was attached to the island just to the north of this and defined the south-western end of a shallow bay choked with a mangrove swamp and bounded on the north by a large flat peninsula.

A pair of islets lie on the north-eastern end of the peninsula, the smaller nicknamed Island 'A' and the larger called Ngabad island. Off the north-eastern end of Peleliu’s long upper arm are two more islands. The larger, approximately L-shaped, Negesebus island is connected with the main island by a causeway 600 yards (550 m) long. The second, but non-operational, Japanese airfield covered the base of the 'L'. Attached by a 100-yard (90-m) causeway was the elongated Kongauru island on Negesebus’s eastern end. Both of these islands are flat, sandy and covered with scrub trees.

The most suitable landing beaches were deemed to be those on the southern portion of the western coast of Peleliu’s south-eastern part, although landings could also be made at almost any point providing the reef and mangroves allowed access. On the island’s eastern side, a reef fringes the southern coast, but is as much as 1,600 yards (1465 m) wide along the northern coast. The north-western side has reefs up to 1 mile (1.6 km) wide, but narrowing to between 600 and 700 yards (550 and 640 m) along the southern portion’s western coast. There it is shallow, but littered with boulders and outcroppings. The outer lip of the reef is raised and the surf is moderate. This lip prevented landing craft from reaching shore and great reliance was placed on amphibian tractors and DUKW amphibious trucks, as well as barge-mounted cranes to transfer supplies and munitions from landing craft to the amtracks and DUKWs. In-depth defences had been dug in facing these beaches and natural obstacles on the reefs were reinforced with man-made obstacles and mines. A rocky islet dubbed Unnamed Island sits on the southern end of these beaches on the northern side of Ngarmoked island on Peleliu’s tip. From this, automatic weapons and anti-boat guns covered the approaches to the beaches.

Major General William H. Rupertus, commander of the 1^st Marine Division, predicted that the island would be secured within four days, but after repeated Imperial Japanese army defeats in previous island campaigns, Japan had developed new island-defence tactics and fixed defences that were well designed and very sturdily constructed, and this made it possible for the Japanese to offer a resistance that was far more effective than Rupertus and other US leaders had expected. This resulted in a battle which lasted more than two months. Although heavily outnumbered, the Japanese defenders put up a resistance so stiff that the island became known to the Japanese as the 'Emperor’s Island'.

In the USA, the 'Battle of Peleliu' became a matter of controversy because of the island’s negligible strategic value and the high casualty rate, which exceeded those of all other amphibious operations during the Pacific War.

By the later part of 1944, US successes in General Douglas MacArthur’s South-West Pacific Area and Admiral Chester W. Nimitz’s Central Pacific Area had brought the war closer to Japan, with US four-engined heavy bombers now able to strike at the Japanese main islands from air bases constructed on the islands which had been secured in the Mariana islands campaign of June to August 1944. At this juncture, there emerged disagreement among the US Joint Chiefs-of-Staff over two proposed strategies to complete the final defeat the Japanese empire. The strategy proposed by MacArthur called for the recapture of the Philippine islands group, followed by the capture of Okinawa, then an attack on the Japanese home islands; that proposed by Nimitz favoured a more direct strategy of bypassing the Philippine islands group, but seizing Okinawa and Taiwan as staging areas for an attack on the Japanese mainland and finally an invasion of the Japanese home islands. Both strategies included the invasion of Peleliu, but for different reasons.

The 1^st Marine Division had already been chosen to make the assault. US President Franklin D. Roosevelt travelled to Pearl Harbor in the Hawaiian islands group to meet both commanders and hear their arguments, and finally opted for MacArthur’s plan. Before MacArthur could invade and retake the Philippine islands group, however, the Palau islands group, and specifically Peleliu and Angaur islands, were to be neutralised and an airfield built to protect MacArthur’s left flank.

By 1944, the island of Peleliu was garrisoned by about 11,000 men of Lieutenant General Sadae Inoue’s 14^th Division, supplemented by Korean and Okinawan labourers. Colonel Kunio Nakagawa, commander of the division’s 2^nd Regiment, supervised the preparations for the island’s defence.

After their losses in the Solomon, Gilbert, Marshall and Mariana island groups, the Imperial Japanese army assembled a research team to develop new tactics and physical concepts for the defence of the islands which the Japanese still held. The team opted for the abandonment of the current concept of trying to stop an invading force on the beaches, where the defending forces were exposed to the landing forces' naval gunfire support. The new tactics were designed only to disrupt the landings at the water’s edge and depend for the most part on an in-depth defence farther inland. In accord with this new doctrine, Nakagawa was able to plan on the basis of using the rough terrain to his advantage by constructing a system of heavily fortified bunkers, caves and underground positions, all interlocked in a 'honeycomb' system. The traditional banzai attack was also discontinued as being both wasteful of men and ineffective. These changes would thus force the US forces into a war of attrition requiring more resources.

Nakagawa’s defences were centred on Peleliu’s highest point, Umurbrogol mountain, a collection of hills and steep ridges in the island’s heart and overlooking a large portion of the island, including the crucial airfield. The Umurbrogol complex contained some 500 limestone caves, connected by tunnels. Many of these were former mine shafts that were turned into defensive positions. Engineers added sliding armoured steel doors with multiple openings to serve both artillery and machine guns. Cave entrances were opened or altered to be slanted as a defense against grenade and flamethrower attacks. The caves and bunkers were connected to a vast tunnel and trench system throughout central Peleliu, which allowed the Japanese to evacuate or reoccupy positions as needed, and to take advantage of shrinking interior lines.

The leaders of the Japanese defence, commanded by Lieutenant General Sadao Inoue’s Palau District Group with its headquarters on Koror island, included Vice Admiral Yoshioka Ito and Major General Kenjiro Murai: Sadao sent Murai to Peleliu to provide sufficiently high army rank to balance the command authority of Ito, who was nominally in command of the Japanese naval forces in the southern part of the Palau islands group. On Peleliu was part of Sadao’s 14^th Division in the form of Nakagawa’s Peleliu Sector Unit comprising the reinforced 2^nd Regiment (2/2^nd Regiment, 3/2^nd Regiment, 3/15^th Regiment and 346/53^rd Independent Mixed Brigade.

The Japanese were well armed with 81-mm (3.19-in) and 150-mm (5.91-in) mortars and 20-mm anti-aircraft cannon, backed by a light tank unit and an anti-aircraft detachment.

The Japanese also used the beach terrain to their advantage. The northern end of the landing beaches faced a 30-ft (9.1-m) coral promontory that overlooked the beaches from a small peninsula, a spot later known to the marines who assaulted it simply as 'The Point'. Holes were blasted into the ridge to accommodate a 47-mm (1.85-in) gun and six 20-mm cannon. The positions were then sealed shut, leaving just a small slit through which to fire on the beaches. Similar positions were created along the 2-mile (3.2-km) stretch of landing beaches.

The beaches were also littered with thousands of obstacles for the landing craft, principally mines and a large number of heavy artillery shells buried with their fuses exposed to explode when any landing craft passed over them. One battalion was placed along the beach to defend against the landing, but it was meant merely to delay the inevitable US island advance.

The US assault forces for 'Stalemate II', under the overall command of Nimitz, were led by Admiral William F. Halsey’s 3^rd Fleet, and comprised Vice Admiral Theodore S. Wilkinson’s Joint Expeditionary Force (Task Force 31) with Smith’s III Amphibious Corps as its Expeditionary Troops (TF36). Major General Roy S. Geiger’s Western Landing Force (Task Group 36.1) was centred for the initial landings on Rupertus’s 1^st Marine Division of three infantry regiments and one artillery regiment. Other units were the 12^th Anti-Aircraft Artillery Battalion, 1^st Amphibian Tractor Battalion, 3^rd Armored Amphibian Tractor Battalion, 4^th, 5^th and 6^th Marine War Dog Platoons, and Underwater Demolition Teams 6 and 7.

Unlike the Japanese, who had effected a major alteration of their tactics for the forthcoming battle, the US invasion plan was essentially unchanged in conceptual terms from that of previous amphibious landings, even after suffering 3,000 casualties and enduring two months of delaying tactics in 'Horlicks' against the entrenched Japanese defenders in the Battle of Biak'. For Peleliu, US planners chose to land on the south-western beaches because of their proximity to the airfield in the south part of the island. The 1^st Marines, commanded by Colonel Lewis B. Puller, were to land on the northern end of the assault on Beaches 1 and 2; the 5^th Marines, under Colonel Harold D. Harris, were to land in the centre on Beaches Orange 1 and 2; and the 7^th Marines, under Colonel Herman H. Hanneken, were to land at the southern end of the assault on Beach Orange 3.

The division’s artillery regiment, the 11^th Marines under Colonel William H. Harrison, was to come ashore after the infantry regiments. The plan was for the 1^st and 7^th Marines to push inland, guarding the 5^th Marines' flanks, and allowing the latter to capture the airfield located directly to the centre of the landing beaches. The 5^th Marines were to push to the eastern shore, cutting the island in half. The 1^st Marines would push north into the Umurbrogol mountain areas, while the 7^th Marines would clear the southern end of the island. Only one battalion was left behind in reserve, with the US Army’s 81^st Division, commanded by Major General Paul W. Mueller, available for support from Angaur island, just to the south of Peleliu.

On 4 September, the marines departed Pavuvu, just to the north of Guadalcanal for their a 2,100-mile (3380-km) passage across the Pacific to Peleliu. An underwater demolition team of the US Navy went in first to clear the beaches of obstacles, while warships began their pre-invasion bombardment of Peleliu on 12 September. The battleships Pennsylvania, Maryland, Mississippi, Tennessee and Idaho, the heavy cruisers Indianapolis, Louisville, Minneapolis and Portland, and the light cruisers Cleveland, Denver and Honolulu, led by the command ship Mount McKinley, subjected the tiny island to a massive three-day gunfire bombardment, interrupted only to permit air attacks from the three fleet carriers, five light carriers and 11 escort carriers with the attack force. Totals of 519 rounds of 16-in (406-mm) shells, 1,845 rounds of 14-in (356-mm) shells and 1,793 500-lb (227-kg) bombs pounded the islands during this period.

The Americans believed the bombardment to have been successful, as Rear Admiral Jesse B. Oldendorf, commander of the heavy ships constituting the Fire Support Group, claimed that the US Navy had run out of targets. In reality, the majority of Japanese positions remained completely unharmed. Even the battalion left to defend the beaches was virtually unscathed. During the assault, the island’s defenders exercised unusually tight fire discipline to avoid giving away their positions. The bombardment managed to destroy only Japan’s aircraft on the island, as well as the buildings surrounding the airfield. The Japanese remained in their fortified positions, ready to fall on the US landing troops.

The US Marines landed on Peleliu at 08.32 on 15 September, the 1^st Marines to the north on Beaches White 1 and 2 and the 5^th Marines and 7^th Marines in the centre and south on Beaches Orange 1, 2 and 3. As the landing craft approached the beaches, the marines were caught in a crossfire when the Japanese opened the steel doors guarding their positions and started to open fire with their artillery. The positions on the coral promontories guarding each flank fired on the marines with 47-mm guns and 20-mm cannon, and by 09.30 the Japanese had destroyed 60 LVTs and DUKWs.

The 1^st Marines were quickly pinned down by heavy fire from the extreme left flank and 'The Point'. Puller’s LVT was hit by a high-velocity artillery round which failed to detonate, and his communications section was destroyed on its way to the beach by a hit from a 47-mm round. The 7^th Marines faced a cluttered Beach Orange 3, with natural and man-made obstacles, forcing the LVTs to approach in column rather than line. 

It was the 5^th Marines whos made the greatest progress on the first day, aided by cover provided by coconut groves.  They pushed toward the airfield, but were met with Nakagawa’s first counterattack. The Japanese tank company raced across the airfield to push the marines back, but was soon engaged by tanks, howitzers, naval guns and dive-bombers. Thus Nakagawa’s tanks and escorting infantry were quickly destroyed.

At the end of the first day, the marines held little more than their 2-mile (3.2-km) stretch of landing beaches. Their biggest push in the south moved 1 mile (1.6 km) inland, but the 1^st Marines to the north made very little progress because of the extreme resistance they met.  The marines had suffered 200 men killed and 900 wounded. Still unaware of the Japanese change of tactics, Rupertus believed the Japanese would quickly crumble since their perimeter had been broken.

On the second day, the 5^th Marines moved to capture the airfield and push toward the eastern shore. They moved quickly across the airfield, enduring heavy artillery fire from the highlands to the north and sustaining heavy casualties in the process. After capturing the airfield, they rapidly advanced to the eastern end of Peleliu, leaving the island’s southern defenders to be destroyed by the 7^th Marines. 

This area was strongly contested by the Japanese, who still occupied numerous pillboxes. The temperature rose to as much as 46° C (115° F), and the marines soon lost many men to heat exhaustion. Further complicating the situation, the marines' water was distributed in empty oil drums, contaminating the water with the oil residue. By the eighth day, however, the 5^th Marines and 7^th Marines had accomplished their objectives, holding the airfield and the southern portion of the island, although the airfield remained under threat of sustained Japanese fire from the heights of Umurbrogol mountain until the end of the battle. Even so, the US forces began using the airfield on the third day of the campaign. Taylorcraft L-2 Grasshopper single-engined observation aircraft of the VMO-3 squadron started to undertake aerial spotting sorties for the marine artillery and naval gunfire. On 26 September, Vought F4U Corsair single-engined fighter-bombers of the marines' VMF-114 squadron landed on the airstrip, and began dive-bombing sorties across Peleliu, firing rockets into open cave entrances for the infantry and dropping napalm; it was only the second time the latter weapon had been used in the Pacific theatre. Napalm proved effective, burning away the vegetation hiding spider holes and usually killing their occupants. The Corsairs' time from take-off to the target area was very short, sometimes only 10 to 15 seconds. Most pilots did not bother to raise their machines' landing gear, leaving it lowered during the air attacks, after which the Corsairs simply turned back into the landing pattern.

The fortress at the end of the southern landing beaches, known as 'The Point', continued to cause heavy marine casualties to the enfilading fire of Japanese heavy machine guns and anti-tank artillery across the landing beaches. Puller ordered Captain George P. Hunt, commander of Company K, 3/1^st Marines, to capture the position. Hunt’s company approached 'The Point' short on supplies, having lost most of its machine guns while approaching the beaches. Hunt’s second platoon was pinned down for nearly a day in an anti-tank ditch between fortifications. The rest of the company was endangered when the Japanese cut a hole in their line, surrounding his company and leaving his right flank isolated. A rifle platoon began knocking out the Japanese gun positions one by one, however, using smoke grenades for concealment and sweeping through each hole, and destroying the positions with rifle grenades and close-quarters combat. After knocking out the six machine gun positions, the marines faced the cave accommodating the 47-mm gun. A lieutenant blinded the Japanese gunner’s fields of vision with a smoke grenade, allowing Corporal Henry W. Hahn to launch a grenade through the cave’s aperture. The grenade detonated the 47-mm gun’s shells, forcing the cave’s occupants out into the open with their bodies alight and their ammunition belts exploding around their waists. A marine fire team was positioned on the flank of the cave and the emerging occupants were shot down.

Company K had captured 'The Point', but Nakagawa counterattacked. The next 30 hours saw another four major counterattacks against a sole company, critically short of supplies, without water, and surrounded. The marines soon had to resort to hand-to-hand combat to fend off the Japanese attackers. By the time reinforcements arrived, the company had repulsed all of the Japanese attacks, but had been reduced to 18 men after suffering the loss of 157 men during the battle for 'The Point'.

After securing the airfield, the 5^th Marines were sent to capture Ngesebus island, just to the north of Peleliu. Ngesebus was occupied by many Japanese artillery positions, and was the site of an airfield still under construction. As noted above, the tiny island was connected to Peleliu by a small causeway, but Harris, the 5^th Marines' commander, opted instead to make a shore-to-shore amphibious landing, appreciating that the causeway was an obvious target for the island’s defenders. Harris co-ordinated a pre-landing bombardment of the island on 28 September, when it was carried out by US Army 155-mm (6.1-in) guns, naval guns, howitzers of the 11^th Marines, strafing runs from VMF-114’s Corsair fighter-bombers, and 75-mm (2.95-in) fire from the approaching LVTs. Unlike the US Navy’s bombardment of Peleliu, Harris’s assault on Ngesebus was successful and killed most of the Japanese defenders. The marines still faced opposition on the ridges and in the caves, but the island fell quickly, with relatively light casualties for the 5^th Marines, which had suffered the loss of 15 men killed and 33 wounded, and inflicted 470 casualties on the Japanese.

After capturing 'The Point', the 1^st Marines moved to the north into the Umurbrogol pocket, named 'Bloody Nose Ridge' by the marines. Puller led his men in numerous assaults, but each resulted in severe losses from Japanese fire. The 1^st Marines were trapped in the narrow paths between the ridges, with each ridge fortification supporting the other with crossfire. The marines continued to suffer increasingly high casualties as they advanced slowly through the ridges. The Japanese again showed unusual fire discipline, striking only when they could inflict maximum casualties. As the marine casualties mounted, Japanese snipers began to take aim at stretcher bearers, knowing that if stretcher bearers were injured or killed, more would have to return to replace them, and the snipers could then steadily pick off increasing numbers of marines. The Japanese also infiltrated the US lines at night to attack the marines in their fighting holes. The marines responded by building two-man fighting holes, so that one marine could sleep while the other kept watch for infiltrators.

One particularly bloody battle on 'Bloody Nose' came when the 1/1^st Marines, under the command of Major Raymond Davis, attacked Hill 100. In six days of fighting, the battalion suffered 71% casualties. Captain Everett Pope and his company penetrated deep into the ridges, leading his remaining 90 men to seize what he thought was Hill 100. It took a day’s fighting to reach what he thought was the crest of the hill, which was in fact another ridge occupied by more Japanese defenders. Trapped at the base of the ridge, Pope set up a small defensive perimeter, which was attacked relentlessly by the Japanese throughout the night. The marines soon ran out of ammunition, and had to fight the attackers with knives and fists, even resorting to throwing coral rock and empty ammunition boxes at their opponents. Pope and his men managed to hold out until dawn, which brought on more deadly fire. When the marines evacuated the position, only nine men remained.

The Japanese eventually inflicted 70% casualties, 1,749 men, on Puller’s 1^st Marines. After six days of fighting in the ridges of Umurbrogol, Geiger, now commander of the III Amphibious Corps, sent elements of the US Army’s 81^st Division to Peleliu to relieve the regiment. The 321^st Regimental Combat Team landed on Peleliu’s western beaches at the northern end of Umurbrogol mountain,on 23 September. The 321^st Regimental Combat Team and the 7^th Marines had encircled 'The Pocket' by 24 September,

By 15 October, the 7^th Marines had suffered 46% casualties and Geiger relieved the regiment with the 5^th Marines. Harris adopted siege tactics, using bulldozers and flamethrower tanks, pushing from the north. On 30 October, the 81^st Division took over command on Peleliu, and took another six weeks, with the same tactics, to reduce 'The Pocket'.

On 24 November, Nakagawa proclaimed 'Our sword is broken and we have run out of spears.' He then burned his regimental colours and committed suicide: he was posthumously promoted to lieutenant general for the bravery he had displayed on Peleliu. On 27 November the island was declared secure, ending the 73-day-long 'Battle of Peleliu'.

One Japanese lieutenant and 26 men of the 2^nd Regiment, together with eight men of the 45^th Guard Force held out in the caves in Peleliu until 22 April 1947, surrendering after a Japanese admiral had convinced them the war was over.

The reduction of the Japanese pocket around Umurbrogol mountain has been called the most difficult fight that the US military encountered in the whole of World War II. The 1^st Marine Division had been mauled and remained out of action until the 'Iceberg' invasion of Okinawa began on 1 April 1945. In total, the 1^st Marine Division suffered more than 6,500 casualties during its month on Peleliu, more than one-third of the entire division. The 81^st Division also suffered heavy losses, totalling 3,300 men, during its final reduction of the island.

After the war, statisticians calculated that it took the US forces more than 1,500 rounds of ammunition to kill each Japanese defender and that, during the course of the battle, the Americans expended 13.32 million rounds of 0.3-in (7.62-mm), 1.52 million rounds of 0.45-in (11.43-mm), 693,657 rounds of 0.5-in (12.7-mm) ammunition, 118,262 hand grenades, and about 150,000 mortar bombs.

The 'Battle of Peleliu' became a matter of controversy in the USA as a result of the island’s lack of strategic value and the high casualty rate. The defenders possessed no means of interfering with potential US operations in the Philippine islands group, and the airfield captured on Peleliu did not play a key role in subsequent operations. Instead, the Ulithi atoll in the Caroline islands group was used as a staging base for the 'Iceberg' invasion of Okinawa. The high casualty rate exceeded those all other amphibious operations during the Pacific War.

In addition, few news reports were published about the battle because Rupertus’s prediction of a four-day victory motivated only six reporters to report from shore. The battle was also overshadowed by MacArthur’s return to the Philippine islands group and the Allies' push toward Germany in Europe.

The 'Battle for Angaur' and the 'Battle of Peleliu' showed the US forces the pattern of future Japanese island defences, but the US forces made few adjustments for the 'Detachment' battle for Iwo Jima and the 'Iceberg' battle for Okinawa. The pre-assault naval bombardment at Iwo Jima was only slightly more effective than that at Peleliu, but at Okinawa the preliminary shelling was much improved. Frogmen performing underwater demolition at Iwo Jima confused the Japanese by sweeping both coasts, but later alerted Japanese defenders to the exact assault beaches at Okinawa. The US ground forces at Peleliu gained experience in assaulting heavily fortified positions such as they would find again on Okinawa.

On the recommendation of Halsey, the planned occupation of Yap island in the Caroline islands group was cancelled. Halsey had actually recommended that the landings on Peleliu and Angaur be cancelled, too, and their marines and soldiers be committed instead to the 'King II' assault on Leyte island, but was overruled by Nimitz.