'Cherryblossom' was the US seizure of a substantial beach-head at Empress Augusta Bay on Bougainville island at the northern end of the Solomon islands group as the final US operation within the eastern portion of 'Cartwheel' (1 November 1943).

The operation was known formally as 'Dipper' (ii), but is universally recognised as 'Cherryblossom', which was the US codename for Empress Augusta Bay.

Bougainville is the largest island of the Solomon islands group, and is about 130 miles (210 km) long and 30 miles (48 km) wide, with an area of 3,598 sq miles (9318 km²). The island lies near the north-western end of the chain, 190 miles (300 km) to the east of Rabaul, the Japanese primary base area in the northern part of New Britain island. Bougainville is mountainous, dominated by the Emperor and Crown Prince ranges, with two active volcanoes of which the higher is Mt Balbi, at 10,171 ft (3100 m). The lower slopes and coastal plains are covered in dense jungle. With an average of some 100 in (254 cm) of rain per year, the island is wet right through the year, although the winter months include south-east winds which bring slightly drier conditions than during the summer period’s north-west winds. Malaria and other tropical diseases are endemic.

Late in 1941, there was an adequate anchorage with a small landing for loading copra at Buin near the southern end of the island, and a grass airstrip. A 1,400-ft (430-m) airstrip had also been completed on Buka island just across the narrow Buka Passage from the northern tip of Bougainville. There were several native trails, mostly along the coast, but only the trail around the north-west coast of the island was usable by motor vehicles. The population was about 54,000 native people speaking about 18 different languages, but only 100 Europeans and 100 Asians, of whom the majority were Chinese.

The evacuation of European women and children was ordered on 12 December 1941, and that of the remaining Europeans on 18 December. Many of the European residents refused to leave, this including many of the island’s missionaries. Many of the Europeans and most of the Chinese were later evacuated, with some difficulty, by submarine. Among those who remained were Jack Read and Paul Mason, who became part of the 'Ferdinand' coastwatcher organisation and transmitted vital early warnings of Japanese air raids against Henderson Field during the Guadalcanal campaign.

Japanese troops landed in the Buka Passage area on 30 March 1942 with the intention of establishing an outer position for the strategic defence of Rabaul, and the airfield on Buka quickly became a useful satellite to the air bases at Rabaul. Occupation of the rest of the island was undertaken only slowly: for example Kieta, in the centre of the eastern coast, was not occupied until July. The Japanese initially made little effort to hunt down the coastwatchers, who operated almost unhindered during the most crucial part of the Guadalcanal campaign.

During their occupation, the Japanese constructed naval aircraft bases in the north, east and south of the island, but none in the west. They developed a naval anchorage at Tonolei harbour near Buin, their largest base, on the southern coastal plain of Bougainville. On the nearby Treasury and Shortland island groups they built airfields, naval bases and anchorages. These bases helped protect Rabaul, the major Japanese garrison and naval base in Papua New Guinea, while allowing continued expansion to the south-east, down the 'chain' of the Solomon islands group, to Guadalcanal and beyond. To the Allies, possession of Bougainville would later also be considered vital for neutralising the Japanese base around Rabaul.

In March and April 1942, the Japanese landed on Bougainville as part of their advance into the South Pacific. At the time, there was only a small Australian garrison on the island: this comprised about 20 men of the 1^st Independent Company and some coastwatchers. Shortly after the Japanese arrived, the bulk of the Australian force was evacuated, although some of the coastwatchers remained behind to provide intelligence. Once the island had been secured, the Japanese began constructing airfields: the main airfields were on Buka island, the Bonis peninsula in the north, Kahili and Kara in the south, and Kieta on the eastern coast. A naval anchorage was constructed at Tonolei harbour near Buin on the southern coastal plain, along with anchorages on the Shortland islands group.

The airfield at Kahili was known by the Japanese as Buin Airfield, and to its south was an airfield on Ballale island in the Shortland islands. These bases allowed the Japanese to conduct operations in the southern part of the Solomon islands group and to attack the Allied lines of communication between the USA, Australia and the South-West Pacific Area.

Bougainville’s native population co-operated with the Japanese more readily than the populations of other islands of the Solomons group. There were a number of reasons for this. The evacuation of the European population proved deeply disturbing to the native population, who rioted at Kieta on 23 January 1942 and were brought under control only by the efforts of one of the German residents who had refused evacuation. The influence of German missionaries and the fact that the Japanese had so easily driven out the Allies also had their effect on the attitude of the natives.

Japanese pressure on the coastwatchers became unbearable, and they were evacuated from the north-east coast in March 1943 by the US submarines Gato and Guardfish. Nine women, 27 children and three nuns were also evacuated.

The airfield at Buka was rapidly improved by the Japanese after the Allied 'Watchtower' landing on Guadalcanal, and boasted a powerplant, underground fuel tanks, and 2,300-ft (700-m) runway surfaced with a mixture of crushed coral and asphalt. By a time late in 1943 the Japanese had completed other airfields at Kahili, Ballale, Kara and Bonism and another was under construction at Kieta. The most southerly airfield, at Kahili, was plagued by rain and harassing air raids, however, and was barely usable by a time late in October 1943.

During 1942, Allied operations in General Douglas MacArthur’s South-West Pacific Area and Vice Admiral Robert L. Ghormley’s (from 18 October Admiral William F. Halsey’s) South Pacific Area were directed at the encirclement and then the capture of the great Japanese base area round Rabaul in 'Cartwheel'. By a time early in 1943 it was clear that this would require the establishment of a ring of air bases around Rabaul, and on 28 February 1943 the Joint Chiefs-of-Staff approved the 'Elkton' strategic plan, which included the invasion of Bougainville by Halsey’s South Pacific Force, which had been established on the basis of a headquarters at Nouméa on New Caledonia island on 18 April 1942. The seizure of part of Bougainville would allow the Allies to construct air bases from which the neutralisation of the Japanese air bases on the rest of Bougainville and on Buka could be undertaken, and also provide fighter cover for Allied bombing raids on Rabaul.

'Elkton' proceeded even after it had been decided not to take the Rabaul area as it was still necessary to encircle and neutralise this great Japanese base.

By the middle of 1943, Bougainville was defended by more than 25,000 men of Lieutenant General Harukichi Hyakutake’s 17^th Army and 12,000 Imperial Japanese navy personnel. This concentration of Japanese strength in heavily fortified positions caused the Allies to re-evaluate their plans, and by a time early in August, Halsey’s planners had proposed an invasion of the Shortland islands group rather than of Bougainville itself.

The Shortland islands group is located just off the southern tip of Bougainville, at the head of 'The Slot'. Shortland island itself is about 13 miles (21 km) long and 10 miles (16 km) wide, relatively flat with a maximum height of 777 ft (237 m), and heavily forested. Most of the coast is fringed by coral reefs, and the nearby small islands are covered with palms. Occupied by the Japanese on 13 March 1942, the anchorage became an important staging area for Japanese forces heading down 'The Slot' to Guadalcanal. The Japanese also established a seaplane base on the island of Faisi and an airfield on the island of Ballale. Faisi later became the headquarters of Vice Admiral Baron Tomoshige Samejima’s 8^th Fleet and was garrisoned by the 5,000 men of the 1^st Base Force.

Ballale airfield was constructed by the 18^th Construction Battalion between November 1942 and January 1943. Lacking bulldozers, the Japanese used some 517 British prisoners of war, primarily artillerymen taken prisoner at the time of Singapore’s surrender in February 1942. The Japanese refused to permit the prisoners to build any kind of air raid shelters, and most of the gunners were eventually killed either in air raids or from Japanese abuse. The survivors were allegedly massacred on 5 March 1943.

The Allies considered seizing the area, but cancelled the invasion plan in August 1943 because of the strength of the defences, the lack of good landing beaches, and the lack of good airfield sites. The area was bypassed by the Allied 'Goodtime' landing in the Treasury islands group to the south-west and 'Cherryblossom' land at Cape Torokina on western Bougainville.

This cancellation came on 7 September, when Halsey’s senior commanders proposed landings in the Treasury islands group and at Choiseul Bay on the northern tip of Choiseul island. Depending on the Japanese reaction, the Allies could then advance either from Choiseul Bay to Kieta, on the east coast of Bougainville, or from the Treasury islands group to Empress Augusta Bay on the west coast of Bougainville. The combination of three factors (the rapid success of the 'Dogeared' operation on Vella Lavella, pressure from MacArthur to land on Bougainville as soon as possible, and lack of available shipping) then led Halsey to adopt yet another plan. The landing on Choiseul would be reduced to the 'Blissful' diversionary raid, and the 'Goodtime' invasion of the Treasury islands group would be followed almost immediately by the landing of the 3^rd Marine Division at Cape Torokina at the northern end of Empress Augusta Bay.

This final plan, issued on 15 October 1943, was unorthodox by the standards of the time. The terrain along most of the coast was coastal swamp, with virtually no road net, but it was also far from the Japanese concentrations in the south, and there were believed to be no more than 1,000 Japanese in the area. Allied planners estimated that it would take three months for the Japanese in the south to organise and implement an effective counterattack, and by that time the Allies planned to have established a secure lodgement including at least one airfield.

The other potential landing site was Kieta, but though this seemed to possess a superior anchorage, it was farther from Rabaul, had better communications with the Japanese garrisons to the south, and would have required the prior seizure of Choiseul. A reconnaissance late in September by submarine-landed parties found that Kieta was in fact a poorer harbour than originally thought, and that the Japanese had all but abandoned the airstrip. By contrast, other reconnaissance parties found that Cape Torokina had no swamps immediately behind the beach, and soil tests at a coconut plantation to the east of Cape Torokina indicated that the soil was capable of supporting an airfield extending parallel with the shore.

To alleviate the shipping shortage, a depot was established on Vella Lavella, which was within tank landing craft range of Cape Torokina. Even so, the troops coming ashore in the first waves would carry only two units of fire. An unprecedentedly comprehensive level of reconnaissance was also carried out, including aerial reconnaissance, hydrographic surveys by submarine, and reconnaissance patrols landed from submarines. To help conceal the Allied intentions, reconnaissance patrols were also landed by submarine on Santa Isabel island, Choiseul island and the Shortland islands group, as well as on the Treasury islands group and at Kieta and Cape Torokina on Bougainville.

The assault force carried out rehearsals in the middle of October at Efate in the New Hebrides islands group and in the Guadalcanal area.

In overall terms, therefore, the Americans had decided after the their 'Toenails' and 'Dogeared' operations to take New Georgia and Vella Lavella islands in the centre of the Solomon islands chain between June and August 1943, to bypass the two next logical steps up the ladder (the small island of Kolombangara and the larger island of Choiseul), and instead land on Bougainville in an operation supported by 'Blissful', a feint designed to persuade the Japanese that the Americans were in fact making a real effort against Choiseul.

The decision to bypass Kolombangara proved to be operationally sound, for even as US forces were securing Vella Lavella, Lieutenant General Minoru Sasaki, commanding the 'Nanto' Detachment, was ordered by Imamura’s 8^th Area Army to save his troops for another day and was shifting the forces on Kolombangara island, between Bougainville and Vella Lavella islands, to Bougainville. On three nights at the end of September and in early October, Japanese barges, landing craft and torpedo boats, under escort by destroyers and aircraft, managed to evacuate more than 9,000 troops, while the efforts of US Navy destroyers to thwart the withdrawal were frustrated by the Japanese escorts. The fight for the central part of the Solomon islands group thus ended with New Georgia, together with all the islands round it, firmly in US hands. More than 1,000 Americans had died in the battle, and nearly four times as many had been wounded. Japanese casualties probably totalled around 10,000, of which at least a quarter had been killed.

Furthermore, continuing Japanese air and naval losses emphasised the growing attrition of these valuable resources at the hands of increasingly rampant US forces. Still, the four-month Japanese defence of the central part of the Solomon islands group meant that the 8^th Area Army had been given that more time to prepare the north-eastern part of New Britain, centred on Rabaul, and the whole of New Ireland for its final defence. On Bougainville, the Japanese hoped to delay the US forces still further.

The importance of this was greater than perhaps they realised. The victories of Halsey’s South Pacific Area command in the southern and central parts of the Solomon islands group had been matched by impressive advances by the army-based forces of MacArthur’s South-West Pacific Area command in New Guinea, and it was this which had persuaded the Joint Chiefs-of-Staff that it would now be more advantageous to bypass and neutralise Rabaul than to capture it, thus freeing large forces for a more rapid drive on targets closer to the Japanese home islands. Ratified by Allied military leaders late in August 1943, this decision left Bougainville as Halsey’s last obstacle before the drive beyond Rabaul.

While pressure was kept on the Japanese by heavy US bombing of Japanese air bases on Bougainville and surrounding islands late in September, Halsey’s staff was planning 'Cherryblossom'. Though precise numbers are still disputed, it seems likely that there were more than 38,000 men of Hyakutake’s 17^th Army on Bougainville, as well as some 20,000 Japanese naval troops. The most important combat formation of the 17^th Army was Lieutenant General Masatane Kanda’s 6^th Division, and Japanese army units which arrived after the US landing were a brigade of Lieutenant General Yasushi Sakai’s 17^th Division from New Britain and the brigade-sized 4^th South Seas Garrison Unit. The Japanese navy could also provide maritime support by means of Kusaka’s twin commands, the South-East Area Fleet and 11^th Air Fleet, both headquartered at Rabaul.

On and round Bougainville, the Japanese deployed their forces in the Buin area (15,000 men of Kanda’s 6^th Division, about 6,800 men of several special naval landing forces, and also the headquarters of the 17^th Army), Buka (5,000 men of Major General Kesao Kijima’s 38^th Independent Mixed Brigade), Kieta (5,000 men of the 6^th Division), and Mosigetta (1,000 men), the last comprising in the main labour force involved in the cultivation of rice as the staple of the garrison’s food supply. The Japanese naval strength was centred on Faisi island off the south-eastern end of Bougainville, and comprised the headquarters of Samejima’s 8^th Fleet, Outer South Seas Force and the 1^st Base Force. The ships of the 8^th Fleet, all based at Rabaul, were the heavy cruisers Myoko and Haguro of Rear Admiral Sentaro Omori’s 5^th Cruiser Division, the light cruisers Sendai and Agano, the destroyers Shigure, Samidare, Shiratsuyu, Naganami, Hatsukaze and Wakatsuki, and five destroyer transports.

Allied intelligence had a fairly good appreciation of this strength, and also of the fact that the bulk of the Japanese strength was concentrated in the area of Buin at the south-eastern tip of the island. Halsey’s staff decided that it made sense to bypass this concentration, a decision facilitated by the fact that what the US forces needed was not the whole island but rather the location for a major air base complex from which Rabaul could be neutralised by bombing and from which the Japanese supply line between Rabaul and the Solomon islands group could be severed: in short, it was not necessary to crush all of Hyakutake’s forces, but merely to bypass and isolate them. And this is exactly what Halsey proposed to do. Thus the fact that most of the Japanese forces were concentrated in the south-eastern part of Bougainville and at the island’s north-western tip, made the practically undefended Empress Augusta Bay area, located mid-way up the western coast, an attractive target.

The date for the 'Cherryblossom' landing on Bougainville was set for 1 November, and the ground task was allocated to Lieutenant General Alexander A. Vandegrift’s I Marine Amphibious Corps delivered and supported by the ships of Rear Admiral Theodore S. Wilkinson’s 3^rd Amphibious Force (Task Force 31). Once landed, the troops were to come under the command of Major General Roy S. Geiger, who was to take command of the I Marine Amphibious Corps when Vandegrift was elevated to the position of Commandant of the Marine Corps on 1 January 1944.

During October, the bombers of Major General George C. Kenney’s 5^th AAF continued to pound the six Japanese airfields on Bougainville, as well as the single airfield on Buka island, knocking out the last of these by the end of the month. To confuse the Japanese further, in the pre-dawn hours of 27 October, a small force of New Zealand troops occupied the Treasury islands, to the south of Bougainville, in 'Goodtime'. Then, later in the same day, a battalion of US Marines landed on the large island of Choiseul to the east. This 'Blissful' operation was merely a raid, but was designed to mislead the Japanese about US intentions.

The Japanese knew that the Allies would soon launch another assault landing on an island of the Solomon islands group, but did not anticipate that the Allies would undertake an amphibious leap of the length represented by 'Cherryblossom'. After some delays resulting from erroneous intelligence suggesting an Allied move in the central Pacific, Admiral Mineichi Koga ordered the air groups from the carriers of his Combined Fleet to join the 11^th Air Fleet at Rabaul in 'Ro' for a pre-emptive attack on the Allied shipping and airfields in the Solomon islands group. Koga also ordered Vice Admiral Eigi Goto’s 12^th Air Fleet in Japan, from which its task was to cover Goto’s own North-East Area Fleet, to prepare to move to Rabaul and come under the command of Vice Admiral Gunichi Mikawa’s South-West Area Fleet, 2^nd Southern Expeditionary Fleet. By 1 November 1943, the air groups of the three fleet carriers Zuikaku, Shokaku and Zuiho (Vice Admiral Jisaburo Ozawa’s 3^rd Fleet), comprising 45 Aichi D3A 'Val' single-engined dive-bombers, 40 Nakajima B5N 'Kate' single-engined level and torpedo bombers, 82 Mitsubishi A6M Reisen 'Zero' single-engined fighters and six reconnaissance aircraft (probably Yokosuka D4Y 'Judy' single-engined machines), had completed the move.

At the same time Kenney’s US 5^th AAF was undertaking an air offensive against Rabaul. Aerial reconnaissance on 11 October revealed that there were 128 bombers and 145 fighters on Rabaul’s airfields, and on the following day launched the largest air attack of the Pacific war up to that time, comprising 213 heavy and medium bombers and 125 Lockheed P-38 Lightning twin-engined long-range fighters. The attack claimed three merchant ships and many smaller vessels sunk, and more than 100 aircraft destroyed on the ground. The claims were, as usual, greater than the actuality. On 2 November, for example, a raid after the arrival of the Japanese reinforcement by carrierborne aircraft, the 5^th AAF lost 10 bomber and nine fighters, but claimed at least 85 Japanese aircraft destroyed and 114,000 tons of shipping sunk, whereas the actuality was 20 aircraft destroyed and 5,100 tons of shipping sunk. Whatever the damage which may or may not have been inflicted, however, the raids were successful in diverting Japanese attention away from Bougainville, and also in damaging ground facilities sufficiently badly to reduce Japanese combat efficiency.

On the other side of the coin, though, the 5^th AAF was worn down to the point that on 29 October Kenney could gather only 53 P-38 fighters and 37 Consolidated B-24 Liberator four-engined heavy bombers for a raid on Rabaul.

The airfields on Bougainville itself were neutralised by Airsols (Air Solomons command), whose aircraft flew 3,259 sorties against Bougainville in October 1943.

At the time of 'Cherryblossom', the I Marine Amphibious Corps comprised Major General Allen H. Turnage’s 3^rd Marine Division, the 2^nd and 3^rd Marine Raider Battalions, the 3^rd Amphibious Tractor Battalion, the 1^st Marine Parachute Battalion (arrived 23 November 1943), the 8^th Brigade Group of the New Zealand 3^rd Division for 'Goodtime', Major General Robert S. Beightler’s 37^th Division (arrived 9 November 1943), Major General John R. Hodge’s Americal Division (arrived 15 December 1943), and the 7^th Advance Naval Base Unit with the 71^st Naval Construction Battalion.

Wilkinson’s 3^rd Amphibious Force included several major elements 1, and benefited from the availability of considerable air power. Longer-range air defence and air support was afforded by Rear Admiral Frederick C. Sherman’s TF38 with the fleet carrier Saratoga (Air Group 12 with 33 Grumman F6F Hellcat single-engined fighters, 16 Grumman TBF Avenger single-engined level and torpedo bombers and 22 Douglas SBD Dauntless single-engined dive-bombers), light fleet carrier Princeton (Air Group 23 with 19 F6F and seven TBF aircraft), the anti-aircraft light cruisers San Diego and San Juan, and nine destroyers.

Land-based air support could be provided by Major General Nathan F. Twining’s Airsols command at Barakoma with 64 Vought F4U Corsair single-engined day fighters, six F4U night-fighters, six Lockheed PV-1 Ventura twin-engined night-fighters and 413 other aircraft; and Kenney’s 5^th AAF at Dobodura with 75 B-25 twin-engined medium bombers, 61 B-24 heavy bombers, 80 P-38 fighters and 133 other aircraft.

The resources available for the support of 'Cherryblossom' were limited by the fact that Nimitz was about to open his 'Galvanic' offensive in the central Pacific. Halsey therefore had only a single carrier group with which to cover the landings, along with cruiser and destroyer forces. A second carrier group had been allotted to the theatre, but this could not arrive before 7 November. Wilkinson was allocated just 12 attack troop and cargo transport ships, supplemented by tank landing ships and other short-range landing craft. The assault troops themselves carried just one unit of fire, though additional ammunition was brought in by attack cargo ships.

Just after 24.00 on 1 November 1943, the day of the main landings at Cape Torokina, the warships of Merrill’s TF39 undertook a gunfire bombardment of Buka for two and a half hours. The ships then raced to the south and undertook a gunfire bombardment of the Shortland islands group. The 'Cherryblossom' landings were also covered by the aircraft of Sherman’s TF38 (Saratoga and the newly arrived Princeton), which launched air attacks on Buka.

Whatever the effect of the 'Goodtime' and 'Blissful' landings, when it was landed by the eight attack troop transports and four attack cargo transports of Task Unit 31.5, the Northern Force of Wilkinson’s TF31 (3^rd Amphibious Force), on the northern shore of Empress Augusta Bay near Cape Torokina early on 1 November met very little Japanese opposition. The approaches to the landing beaches were poorly charted, but the designated transport area was found to be free of shoals. The landings were themselves extremely well organised, with the first assault waves of Turnage’s 3^rd Marine Division coming ashore from 07.26, a mere 41 minutes after their transports had anchored, and almost 8,000 men were ashore within two hours. However, heavy surf took its toll of the landing craft, of which more than 30 were wrecked during the landings.

The 14,321 men of Turnage’s 3^rd Marine Division were faced by a mere 270 or so Japanese soldiers of the 2^nd Company, 2/23^rd Regiment of the 6^th Division in the landing area, but these were concentrated around Cape Torokina itself and gave the southern element of the landings short but significant difficulty. There were about 25 Japanese pillboxes in this area, and their single 75-mm (2.95-in) gun, concealed in a coconut log and sand bunker, managed to sink four landing craft and damage several others. The personnel landing craft containing the senior officer of the initial assault was one of those hit, and this threw the landing of 1/3^rd Marines into disarray. Sergeant Robert A. Owens led an attack which knocked out the gun but cost him his own life. The battalion commander, Major Leonard M. Mason, was wounded but managed to restore order before being evacuated.

It was later noted that the pre-landing gunfire bombardment had been almost completely ineffective. The 'Longsuit' landing on Betio island of Tarawa atoll was still three weeks in the future within 'Galvanic', and it was the US losses in this bloodbath rather than 'Cherryblossom' which provided absolute proof of the overwhelming importance of highly accurate naval gunfire from the closest possible range. Moreover, Wilkinson later noted that many ships fired short for more than five minutes before correcting their aim.

The 3^rd Marine Raider Battalion was assigned to land on Puruata island, just off Cape Torokina, where there was a platoon of Japanese defenders. These men resisted fiercely in spite of being heavily outnumbered, but by 15.30 on 2 November the island had been cleared, some 29 Japanese being killed at a cost of five marines killed and 32 wounded.

Unloading on Cape Torokina was interrupted at 07.35 by the attack of nine D3A dive-bombers and 44 A6M fighters, but the damage inflicted by the Japanese warplanes was negligible. A second attack at 13.00 by about 100 naval aircraft achieved little more than forcing one transport vessel to run aground, though only for a short time. The Americans claimed some 15 Japanese aircraft shot down, and the worst consequence of the raids was that unloading of supplies was delayed by four hours.

Only 68 of the Japanese defenders escaped the initial advance of the marines, whose casualties were 78 men killed and 104 wounded.

In fact the terrain had been a greater obstacle than the Japanese on the northern beaches. The beach was essentially a large sand bar between the ocean and nearly impenetrable swamp, with only isolated small areas of just slightly higher ground. Given the fact that the terrain around the bay was low and wet, the Japanese had thought it unsuitable for an amphibious assault and thus made only the most limited defensive preparations: thus fewer than 300 men had been deployed to Empress Augusta Bay, and these were overwhelmed in short order as, within just a few hours, Vandegrift’s men secured the area.

The attack cargo ships were only lightly loaded, with no more than 550 tons apiece, to ensure that these supplies could be landed as swiftly as possible. By 17.30 eight of the ships were fully unloaded, putting 14,000 men and 6,200 tons of supplies ashore. The LVTs of 3^rd Amphibious Tractor Battalion made n especially important contribution to moving supplies over the swampy ground. Some 29 LVTs landed on the first day, and eventually 124 LVTs operated with the marines. All the transport ships pulled back at 18.00, but the four still carrying essential supplies and equipment were then detached to return and finish unloading. These ships retreated once again when a scouting aeroplane reported that Japanese warships were departing Rabaul, then returned following the Allied victory in the Battle of Empress Augusta Bay.

After unsuccessful air attacks had been flown from Rabaul, Samejima’s 8^th Fleet committed almost all of its available strength to an assault on the US invasion fleet. Thus the inevitable Japanese counterattack came by air and sea rather than on land. As noted above, almost immediately after the Japanese had learned of the landing at Cape Torokina, Rabaul-based bombers and fighters had been despatched to strike at the landing force, only to be driven off with heavy losses by the defending US aircraft. At the same time, a strong force of Japanese navy cruisers and destroyers now steamed to the south-east to tackle and destroy the US invasion force, and this undertaking led to the Battle of Empress Augusta Bay, known to the Japanese as the Battle of Gazelle Bay.

Omori happened to be in Rabaul on 30 October, having escorted a convoy supplying the 8^th Fleet with additional ships. At a time later on the following day, Omori despatched a force of two heavy cruisers, two light cruisers and two destroyers on a sweep. This force could have posed a considerable threat to Wilkinson’s invasion force if contact had been made, but the Japanese failed to find the Americans and returned to Rabaul, only then to learn that the Americans had already landed at Cape Torokina.

Omori at once received approval from Koga, commanding the Combined Fleet from the great base at Truk in the Caroline islands group, to combine his force with that of Samejima in order to escort 1,000 Japanese troops to Empress Augusta Bay for a land counterattack, while at the same time the Japanese naval force attacked and destroyed the transports and the supporting US naval force. Omori’s transports could not be made ready in time, but the admiral received permission to proceed to Torokina Point, where he would await his transports and then attack the US transports which he believed to be there.

Omori sailed into the St George Channel to await the transports, but when they arrived he found them too slow for his operation, and left them in the St George Channel at 19.30. Coming north to meet him was Merrill’s TF39, which had just returned to base from bombarding Buka airfield on 31 October. Just before contact was made in the 'Battle of Empress Augusta Bay', at a point some 22 miles (25 km) to the north-west by west of Torokina Point the Japanese forces were steaming in three columns. On the port side was the light cruiser Sendai leading the destroyers Shigure, Samidare and Shiratsuyu; some 10,000 yards (9145 m) to starboard was the central column, comprising the heavy cruisers Myoko and Haguro; and 5,000 yards (4570 m) still farther to starboard was the light cruiser Agano with the destroyers Naganami, Hatsukaze and Wakatsuki. All three columns were steaming to the south-east.

On a northerly course was TF39 with its four light cruisers (Montpelier, Cleveland, Columbia and Denver) in column, screened at a distance of 1,000 yards (915 m) on their starboard side by the van destroyers, and on their port side by the trailing destroyers. At the point of first contact, the Japanese force was almost 20,000 yards (18290 m) to the north-west of TF39.

The visibility was poor, the Japanese ships lacked radar, an Omori commanded ineptly: he was confused by the reports of his reconnaissance floatplanes, he attempted manoeuvres which were too complex for a force whose ships had not trained together and, perhaps most importantly of all, he had no idea of the strength and nature of the US force opposing him. First, a reconnaissance floatplane reported three US battleships and many cruisers and destroyers at Torokina Point. Then at 01.26 Haguro catapult-launched a floatplane which at 01.40 reported minelayers, one cruiser and three destroyers at a location some 23 miles (37 km) to the south of the Japanese ships. Desiring both to confuse the US commander and to buy the time for further air reconnaissance reports, Omori then ordered a 180° simultaneous turn, a difficult manoeuvre for his tightly spaced ships, especially as they were operating in total darkness. A short time later he ordered another 180° simultaneous turn. By this time his columns were in some disorder: the port screen was only about 300 yards (275 m) away from the main column, and Samidare was out of line. Shortly after this one of Shigure's lookouts sighted US ships, which completely surprised Omori.

TF39 had been heading due north at high speed, and Montpelier's radar had already detected Sendai's screen. At 01.31 Merrill ordered his four van destroyers to veer off to port to attack the Japanese ships. Eight minutes later, Merrill’s group executed a simultaneous turn which would free the rearguard destroyers for a second torpedo attack. One minute after Shigure's sighting, Ausburne, Dyson, Stanley and Claxton launched 25 torpedoes and then split into two units, the first two destroyers reversing course to starboard, the latter two doing the same, but then continuing their loop so that they were closing the light cruisers. Shigure reported seeing two destroyers retiring and two paralleling Sendai's column, and Sendai reacted with a hard turn to starboard, because it was likely that US torpedoes were headed for the column’s flank.

But the earlier loss of formation now caused trouble, for Sendai's turn was sharper than that of Shigure and the two ships almost collided. In trying to avoid Sendai, Samidare collided with the side of Shiratsuyu, which was moderately badly damaged. Both ships were now effectively out of the battle, although Samidare did manage to launch eight torpedoes at 01.52. Shigure launched an eight-torpedo spread at 01.48, and Sendai a similar spread at 01.50.

But now the US light cruisers had gone into action, opening fire at 01.50, and, as usual, the US guns, controlled by radar, were all trained on the largest target. At 01.51 Sendai was hit by the first three salvoes from the four cruisers' 6-in (152-mm) guns. She was almost literally smothered by flying metal, and erupted in flame. Omori in Myoko was startled to see Sendai on fire on his port beam, for he thought Sendai was ahead of him, in the port van. He tried to re-form his ships by turning to port onto a south-south-westerly heading.

In the meantime Agano and its three destroyers closed the US ships, and when the order to re-form came, Agano's group turned in column hard to starboard, causing Myoko and Haguro to cut directly through the column. Myoko sliced off Hatsukaze's bow and smashed the destroyer’s torpedo tubes. Haguro only just missed a collision with Naganami and Wakatsuki.

In response, Merrill’s light cruisers had been executing complicated manoeuvres, but as Myoko and Haguro finally set their course straight to the south, the US light cruisers headed to the south-west, four abreast, gradually edging into a westerly course, and then into a single column steaming due north.

Finally a fire fight between the two Japanese heavy cruisers and four US light cruisers broke out. Myoko and Haguro opened fire at 02.15 and in turn were straddled by American fire. They launched 24 torpedoes at 02.18, but neither side scored, and at 02.29 Omori ordered his ships to withdraw. The US rearguard destroyers did not deliver the torpedo charge expected of them, and Foote managed to blunder into a torpedo aimed at the cruiser column and had her stern blown off, but was then towed to safer waters.

The Japanese had clearly lost this battle, even though they had the heavier guns. Sendai soon sank. The submarine I-144 picked up Rear Admiral Baron Matsuji Ijuin and 37 more of the cruiser’s complement, but the rest of the crew (her normal complement was 450) was lost. US destroyers later sank the bowless Hatsukaze with gunfire after all but nine of her crew had been rescued. Samidare suffered two direct hits, but with collision damage and on manual steering, she regained Rabaul, as did Shiratsuyu. Agano suffered minor damage from a near miss, and Haguro's and Myoko's action reports indicate neither casualties nor damage. With the exception of Sendai, Omori’s manoeuvres and collisions hurt him more than did the torrent of 5- and 6-in (127- and 152-mm) shells and the many torpedoes which had been launched at his force. The US Navy lost 19 men killed, while the Japanese navy suffered between 421 and 581 men killed.

Because Omori was turned back, the US invasion of Bougainville could not be stopped, especially after no greater success attended the several Japanese air attacks of the following day on the US beach-head.

The defeat of Omori’s force persuaded Koga that he had to reinforce the 8^th Fleet at Rabaul as a US foothold on Bougainville could not be tolerated. He therefore detached to Rabaul the heavy cruisers Atago, Chokai, Maya, Takao, Mogami, Suzuya and Chikuma, screened by the light cruiser Noshiro and four destroyers, of Vice Admiral Takeo Kurita’s 2^nd Fleet (Diversion Attack Force). Kurita then assumed local command.

When the news of this Japanese reinforcement reached Halsey, there were no US battleships or heavy cruisers available to him as all the US heavy warships were in the Central Pacific preparing for 'Galvanic' against Tarawa and Makin atolls in the Gilbert islands group. What Halsey did have was Sherman’s TF38, a fast carrier force built around the fleet carrier Saratoga and light carrier Princeton. Fearing that he might lose one if not both of the carriers, Halsey nonetheless took the gamble of sending them to a launch point to the south of Torokina Point, some 265 miles (425 km) to the south-east of Rabaul, and launching all their aircraft at once, relying on surprise and a small combat air patrol provided by the Aircraft Solomons command.

The weather favoured TF38, for Sherman steamed to the north under cloud and in heavy rain, and although they were seen by aerial reconnaissance, the US ships were not recognised as carriers, the Japanese instead believing that the force was a reinforcement group steaming to cover the Bougainville landing.

The Japanese task force arrived on 5 November at about 07.00, and at Rabaul joined the light cruisers Agano and Yubari as well as seven destroyers.

The weather at Rabaul was bright and clear, which was perfect for a surprise air raid. When the air raid signal sounded some time after 10.00, most of the ships were in no condition to get under way and so leave the harbour for dispersal. Saratoga and Princeton had launched their aircraft at 09.00, despatching 52 F6F fighters, 23 TBF torpedo bombers and 22 SBD dive-bombers. These aircraft were first seen at Rabaul at about 10.20. The pilots kept their aircraft in a compact group until the moment of attack, so that they would have maximum protection against the Japanese fighters up to the very last moment. The raid lasted until about 10.44, causing heavy damage to the Japanese ships.

Atago suffered three near misses, her torpedo flasks were exploded, her hull, armament and machinery were damaged, and 22 men were killed and another 64 wounded. Maya had started to leave harbour but was hit on her catapult flight deck: a chain of explosions and fires gutted all her engine rooms, making navigation impossible, and 70 men were killed and another 60 wounded. Chikuma escaped comparatively lightly, with some slight damage to her hull, armament and machinery, and she was able to leave for Truk at 20.38, and steam for Eniwetok on 20 November. Mogami cleared the harbour at 10.37, but before that she had been hit and set on fire, probably by a torpedo. The magazines for the Nos 1 and 2 turrets were flooded. At 10.45 she stopped all engines and concentrated on fire-fighting. That evening, because of the damage to her bow, she departed for Truk under escort of Suzuya and the destroyer Tamanami. Takao received a bomb hit on the starboard side of her No. 2 turret, heavily damaging her hull and machinery. Suzuya, which was just moving up to the oiler Naruto for refuelling when the attack started, took evasive action and escaped with just light damage.

The light cruisers Agano, Noshiro and Yubari received no damage. Of the destroyers, Fujinami was hit by a torpedo whose warhead failed to detonate, and Amagiri and Wakatsuki suffered only light damage.

Having lost a mere 10 of their own number, the US aircraft then returned to their carriers, which sped away to the south without being detected. No sooner had the Japanese fleet begun to sort out the disorder than an attack by aircraft of the 5^th AAF struck the fleet again, this time with a force comprising 27 B-24 heavy bombers and 67 P-38 fighters. The aircraft encountered no opposition in the air as the Japanese warplanes based round Rabaul were out looking for TF38, but despite this fact the US land-based aircraft attack inflicted no further damage on the Japanese warships.

This event was arguably the beginning of the end for Rabaul as a Japanese naval base, although it would take many more raids to drive the Japanese out. The 2^nd Fleet's heavy cruisers, which had been withheld from battle during most of 1943, had suffered grievously at Rabaul: four of them had to be returned to Japan for repair, and would therefore be unavailable for months. The 5^th AAF kept up the pressure with frequent raids. The loss of Japanese aircraft for the defence of Rabaul was serious, but the Japanese navy still desperately needed to use the base and Koga therefore flew in 100 aircraft from his fleet carriers at Truk, further depleting the carriers' supply of warplanes and crews.

TF38’s attack had been so successful that it set the pattern for the US carrier raids of the future, and such raids were one of the three principal factors later said by General Hideki Tojo, the Japanese prime minister for much of the Pacific war, to have caused Japan’s defeat.

Halsey planned an immediate repeat attack. He had just secured the fleet carriers Bunker Hill and Essex, as well as the light carrier Independence, and by 8 November had established Task Group 50.3 under Rear Admiral Alfred E. Montgomery. TG50.3 launched 180 aircraft on 11 November, but this time the Japanese were ready. They not only defended Rabaul’s Simpson Harbour, but also prepared a return attack against the carriers.

The US carrierborne warplanes found fewer targets: inside and outside Simpson Harbour were the heavy cruiser Maya, the light cruisers Agano, Noshiro and Yubari, and the destroyers Kazagumo, Urakaze, Suzunami, Hayanami, Fumizuki, Umikaze, Naganami, Makinami, Fujinami and Amagiri.

The Japanese fighters sent forward to Rabaul from the Truk-based fleet carriers were already aloft, and the US attack force was not flying with the same precision that it had shown before. Nevertheless, Noshiro was attacked by torpedo bombers outside the harbour at 08.57, while a fierce rainstorm was in progress. She evaded the torpedoes but was strafed and suffered limited damage, and then at 09.03 was again subjected to a torpedo attack which also failed. Suzunami was dive-bombed and sunk at 08.20, while Yubari, Urakaze and Umikaze each suffered slight damage. Naganami took a near miss, was then struck by a bomb on her deck abaft the bridge, and had to be towed back into Rabaul.

This second US carrier raid had lasted less than one hour.

At 12.00, the Japanese launched a force of more than 100 aircraft against TG50.3. The US ships' combat air patrols and screening destroyers protected their charges well, however, and the Japanese aircraft scored no hits while also losing more than 35 of their number. Over Rabaul another 20 Japanese aircraft were downed, and thus a mere 52 of the machines sent from the Japanese carriers returned to Truk. Not only had Rabaul been defended ineffectually, but the Combined Fleet carriers had lost so many carrier pilots that Koga could not respond to the US forces' 20 November 'Galvanic' landing on Tarawa.

As in many other similar cases, the Japanese reluctance to lose one part of their defence perimeter allowed another part to be overrun, and now even the original defence perimeter was beginning to collapse because of inadequate naval support. So effective had been the two US carrierborne air attacks in decimating Japanese ship and aircraft strengths in New Britain that the surviving Japanese warships were pulled back to more northerly bases, most notably Truk, thus ending the chances of further naval attacks on the US beach-head on Bougainville.

Japanese air strength also suffered badly. A sustained air offensive on Empress Augusta Bay, lasting for the 10 days following the marines' landing, was a total failure in which the Japanese suffered heavy losses for little gain. By 12 November, with the Japanese naval forces withdrawn from Rabaul, which now accommodated little or no air strength, the great Japanese base was no longer an offensive threat.

Meanwhile, on Bougainville the 'Seabees' of the 71^st Naval Construction Battalion had started work during 4 November on a fighter airstrip, 5,150 ft (1570 m) long and 200 ft (60m) wide, near the coast just to the south-east of Cape Torokina with the support of elements of the 53^rd Naval Construction Battalion and marine labour parties.

Meanwhile, by 5 November, the marine landings had secured a beach-head extending some 2,000 yards (1830 m) inland at the cost of fewer than 200 casualties. A second echelon of troops arrived on this same day under cover by Merrill’s task force.

In response to the US 'Cherryblossom' landing round Cape Torokina, Imamura decided that a counterattack had to be made with the least possible delay. Not fulyy appreciating the size of the US assault forces, the Japanese despatched a force of 850 soldiers to execute a counter-landing as the first step in their attempt to drive the US forces back into the sea.

In response to the US landings on 1 November, Imamura had decided to send a force to counter the landing. The initial concept was to deploy about 3,000 men from Rabaul, but US air and naval strength prevented this and Imamura then opted for a smaller force. Hyakutake, the Japanese commander on Bougainville, therefore despatched a large group of reinforcements from the 23^rd Regiment from the main Japanese position around Buin, on the southern tip of Bougainville to assault the right flank of the US lodgement. At the same time a force of 475 men was sent from Rabaul to the Torokina area to make a counter-landing on the left flank in co-ordination with the assault on the right, and another 700 men were sent to reinforce the Japanese garrison at Buka. These troops were drawn from the 17^th Division and included several companies of the 53^rd Regiment and 54^th Regiments. With the addition of support and service troops, the Japanese landing force totalled some 850 men.

The Japanese estimated US strength in the area to be between 5,000 and 10,000 men, but the real figure was more than 14,000 troops landed around Cape Torokina on the first day. These were followed by another 3,500 men on 6 November. These troops were the main strength of Turnage’s 3^rd Marine Division, which had been sent ashore as part of Wilkinson’s 3^rd Fleet Amphibious Forces. Since the initial landing, Turnage, assisted by Brigadier General Oscar R. Cauldwell, had been in tactical command of the US troops ashore while Lieutenant General Alexander A. Vandegrift returned to Guadalcanal with Wilkinson. As Japanese resistance to the landing declined, Turnage began the reorganisation of his units round the Torokina perimeter, establishing patrols and unloading supplies, and starting base development work.

The Japanese force departed for Bougainville on the night of 1/2 November, but was sighted by US aircraft. A major US force was soon despatched to respond. This convinced the Japanese that a counter-landing at this time would be difficult, so the attempt was postponed and the troops were recalled to Rabaul. Japanese losses sustained in the course of the naval 'Battle of Empress Augusta Bay' further delayed the second sailing of the force and another attempt was cancelled on 5 November after a US air raid. The landing force finally departed Rabaul on 6 November, aboard four destroyers. These were covered by a force, under the command of Rear Admiral Morikazu Osugi, comprising the light cruiser Agano and the destroyers Naganami, Wakatsuki, Shigure, Samidare, Shiratsuyu and Amagiri of the 10^th Destroyer Squadron.

Soon after 00.00, the transport group entered the planned landing area, but the first attempt to effect the landing was quickly abandoned when US ships were seen to be blocking the way. The destroyers headed to the north once again and back-tracked closer to the coast for a second attempt. A light naval force, totalling eight PT-boats, had been established by the US Navy around Puruata island, but none of these boats detected the Japanese ships, which unloaded the embarked troops about 2 miles (3.2 km) from the beach in Atsinima Bay to approach the coast in 21 ramped barges, cutters and motor boats. The landing force was put ashore near the Laruma river and Koromokina lagoon without meeting any immediate response. The plan for the landing had included a naval gunfire bombardment, but the nearby presence of US major warships meant that this was not carried out. Having landed their troops, the Japanese destroyers withdrew.

The US marines were at first confused by the landings, believing that the landing craft they saw were American, and this confusion accordingly delayed the marines' response. Meanwhile, Japanese troops moved to isolate a marine outpost, which was withdrawn during the following day by naval landing craft, and occupied several defensive positions that had been abandoned by the marines the day before during Turnage’s reorganisation. After a Japanese barge was sighted about 4 miles (6.4 km) to the north of Cape Torokina, a PT-boat was sent to investigate; however, reports from marines of the 3^rd Marine Division on that flank of the beach-head confirmed that Japanese barges were landing troops at scattered points along the shore and that the marines were now engaging them. Artillery fire from the gun s of the 12^th Marine Regiment, coast-defence guns and 90-mm (3.5-in) anti-aircraft batteries of the 3^rd Defense Battalion under Lieutenant Colonel Edward H. Forney opened fire on the Japanese barges and landing beaches. The Japanese landings was scattered over a wide area, as was often the case at night and in conditions of rough surf. Unable to concentrate quickly, the Japanese were initially forced to attack in small numbers: the first attack was delivered by fewer than 100 men.

The 3/9^th Marines, commanded by Lieutenant Colonel Walter Asmuth, was allocated the mission of stopping the Japanese counter-landing, and Asmuth called down artillery support fire along the perimeter’s front and the beach. At 08.20, Company K of the 3/9^th Marines boosted by a platoon of the regimental weapons company departed to tackle the Japanese landing. About 150 yards (140 m) from the centre of the Japanese resistance, the advancing marines struck the Japanese force which, seeking cover from the artillery fire, had rapidly prepared itself for defence and, taking advantage of abandoned foxholes and emplacements of the departed 1 and 2/9^th Marines, had established a hasty but effective defensive position.

Heavy fighting broke out, the Japanese firing light machine guns from well-concealed defences covered by automatic rifle fire by snipers hidden in trees. Company K’s attack became pinned as the American advance was halted. Japanese resistance increased as reinforcements from the remainder of the counter-landing force began to arrive. At 13.15, the 1/3^rd Marines was ordered into the fray from reserve, entering the fight after being transferred from the right flank of the US beach-head. Company K provided covering fire while Company B moved across the left flank and passed through Company K to take up the fight. Company C of the same battalion advanced on the right flank and Company K withdrew, having lost five killed and 13 wounded, of whom two later died.

The two companies of the 1/3^rd Marines, under the command of Major John P. Brody, found their task difficult as the Japanese positions were well concealed and they were subjected to heavy machine gun and automatic weapons fire. Then US tanks moved up to help with the assault, and the marines ground their way forward as the fire of the tank destroyed the Japanese emplacements. Late in the afternoon the marines' advance was halted as there began a heavy artillery bombardment of the Japanese positions as a preparation for a full-scale attack by the 1/21^st Marines. The artillery smashed through the Japanese positions, and Companies B and C placed the fire of mortars almost on top of their own positions.

The attack of the 1/21^st Marines, under the command of Lieutenant Colonel Ernest W. Fry, was scheduled to begin at 17.00, but was postponed until the next morning. Right through the night of 7/8 November, small groups of Japanese pushed through US defensive lines, threatening the field hospital which had been established by the 3^rd Medical Battalion. A defence was swiftly mounted by rear-echelon troops, who drove back the Japanese attack and thereby shielded the field hospital.

Several small marine units had been cut off from the main force during 7 November. One of these was a platoon from Company K of the 3/9^th Marines, which had been despatched to reconnoitre the part of the Laruma river area, to the north-west of the location of the Japanese beach-head at Koromokina lagoon, and ambushed a pursuing Japanese patrol several times before escaping into the interior. The platoon returned to the marines' lines 30 hours later with one man wounded and another missing after, but inflicting a number of casualties on the Japanese landing force. Another patrol from Company M of the 3/9^th Marines was cut off on the beach between the two Japanese forces, and when the radio of the patrol’s radio officer failed, he headed back to the main lines directing an artillery barrage that landed on the Japanese position to the left of the patrol from Company M. The patrol then moved toward the marines' line, only to find the beach blocked by Japanese forces opposing Company K. The marines then wrote a message in the beach’s sand, and this was seen by an air spotter: this paved the way for two tank lighters to evacuate the 60-man patrol from the beach after it had killed an estimated 35 Japanese. Only two of the marines had been wounded.

Two other marine groups became isolated in the fighting along the perimeter. One platoon from the 1/3^rd Marines, which was scouting the Japanese flank position, slipped through the jungle and passed the Japanese without being observed. Choosing to head for the beach instead of the interior, the platoon struggled to the coast. There, the patrol cleaned its weapons with petrol from a wrecked barge, and spent the night in the jungle. In the morning of the following day, the marines caught the attention of a US warplane, and less than 60 minutes later the platoon was picked up by a tank lighter and returned to the main lines. The other isolated unit, a patrol of Company B, was cut off from the rest of the battalion during the fighting and spent the night of 7/8 November behind Japanese lines without detection.

After a 20-minute preparatory bombardment by five batteries of artillery together with machine gun, mortar and anti-tank gun fire on the morning of 8 November, the 1/21^st Marines passed through the lines of the 1/3^rd Marines and began the US attack with the support of light tanks. Only a few Japanese soldiers resisted the attack, and these were either killed or captured. More than 250 dead Japanese were found in the area. Moving about 1,500 yards (1370 m) through the jungle parallel to the shore, the marines met no further opposition. During the afternoon of the same day, the marines created a defensive line behind a lagoon, and sent out extensive patrols, none of which made any contact with the Japanese.

On the morning of 9 November, the area between the marine positions and the Laruma river was bombed and strafed by US dive-bombers operating from Munda airfield on New Georgia island. Patrols found the bodies of many Japanese who had taken refuge in the Laruma river area. There was no further Japanese activity on the left flank of the perimeter, and at 12.00 on the same day control of the sector was transferred to the 148^th Infantry of the 37^th Division, which had just arrived. The battalion of the 9^th Marines moved to the right flank, and the 1/3^rd Marines withdrew to the regiment’s main area. The 1/21^st Marines held the left flank and remained under operational control of the 148^th Infantry until other units of the 37^th Division arrived.

The Japanese attempt to destroy the Allied landing force by counter-landing had failed, largely as a result of the Japanese commanders' gross underestimation of the size of the US landing forces, and also their inability to co-ordinate their actions on each sides of the perimeter. Of the 850 men despatched, a mere 475 had been landed. At least 377 men were killed, and the survivors withdrew into the jungle, most of them then being killed in artillery barrages and air attacks between 7 and 9 November. For the Japanese, the landing site was also an unfortunate choice: its location was very close to that of the AUS beach-head, which the Japanese believed to be farther to the east around Cape Torokina. In addition, the Japanese had chosen to assault over a front so large that they had been unable to concentrate in sufficient numbers to take advantage of the initial surprise they had achieved. The marines lost 17 men killed and 30 wounded.

On 9 November, Major General Roy Geiger assumed command of I Marine Amphibious Corps, replacing Vandegrift. Four days later, Geiger assumed command of all Allied forces on Bougainville and adjacent areas. After the end of the fighting round Koromokina lagoon, the 23^rd Regiment began arriving from the south, and subsequently launched an attack on a US force holding a roadblock around the junction of the Piva and Numa Numa trails, which were important avenues of approach toward the US beach-head. The subsequent 'Battle for the Piva Trail' resulted in heavy casualties for the Japanese, totalling some 550 men killed.From this point onward, US Army forces started to reach Bougainville to reinforce and later replace the marines as further echelons arrived at Cape Torokina, bringing more supplies and expanding the size of US forces on Bougainville still further. Another 5,715 men had landed on 8 November, followed by another 3,599 and 6,678 on 11 and 13 November respectively. With the beach-head secured into a useful lodgement, and tactical command transitioned ashore, US forces slowly pushed their perimeter forward, systematically advancing to several inland defence lines, resulting in further actions around Coconut Grove, Piva Forks, Hellzapoppin Ridge and Hill 600A.

Japanese commanders had initially believed that the landing at Cape Torokina was only temporary and would be followed by a larger assault on Buka. As a result, they delayed the launch of any concerted counterattack even though there were up to 15,000 troops available in the southern part of Bougainville island. Meanwhile, further developments saw the construction of several US airfields inside the Torokina perimeter, and these came into service for the projection of US air power toward the main Japanese base at Rabaul, while Japanese sea lanes of communication between Rabaul and Bougainville were heavily interdicted. As the conditions necessary for a large-scale counterattack faded, Hyatukake commander of the 17^th Army, was ordered to delay his plans, postponing the assault on Torokina until March 1944.

As they swept the Koromokina area after the defeat of the Japanese landing force, the marines discovered documents indicating that Imamura’s 8^th Area Army had planned to land 3,000 men in three echelons close to the marine perimeter with the task of infiltrating the perimeter while two battalions of the 23^rd Regiment concentrated just to the east of the Piva river and then attacked the eastern side of the marines' perimeter. However, the destruction of the first landing echelon dissuaded Imamura from any further counter-landing attempts close to the marines' perimeter.

The 23^rd Regiment meanwhile made probing attacks on the marines' perimeter, just to the west of the Piva river, on 5 November but ran straight into a roadblock manned by elements of the 2^nd Raider Battalion on Mission Trail, which the main trail from the area of Cape Torokina to the east. The 23^rd Regiment attacked the roadblock on 7 November in an effort timed to coincide with the counter-landing at Koromokina Lagoon, but was repulsed by the 2^nd Raider Battalion supported by heavy mortar fire. A second Japanese attack on 8 November was preceded by a four-hour mortar bombardment, but the 2^nd Raider Battalion again held, then counterattacked in the early afternoon. By afternoon the next day the Japanese resistance had crumbled, but the marines advanced only a short distance before halting and digging in around the village of Piva.

Between 8 and 13 November the Japanese made three major raids against shipping near Cape Torokina, making wildly exaggerated claims to have sunk US battleships and carriers. In fact, the worst damage was two bomb hits and one torpedo hit on the light cruiser Birmingham, which little impaired its fighting capacity, and one torpedo hit on one of the engine rooms of the light cruiser Denver, which was forced to retire at low speed. These results cost the Japanese 121 out of the 173 carrierborne aircraft which had been committed to Rabaul on 1 November, with 86 aircrew lost. Similar casualties were suffered by the 11^th Air Fleet. The Japanese air attacks did nothing to halt the arrival of Beightler’s 37^th Division as a reinforcement for the marines from 9 November.

While the marines were securing their perimeter, 'Seabees' accompanied by an infantry patrol had identified good ground for airstrips near a coconut grove well to the north of the current marine perimeter. The 'Seabees' cleared the two 5,000-ft (1525-m) 'Piva Fields' airstrips before returning to the perimeter. Because the marines were having some difficulty expanding the perimeter in the very difficult terrain, Turnage ordered the 2/21^st Marines to move forward on 13 November and establish an outpost at a trail junction near the airfield site, where the battalion was to remain until the perimeter could be expanded. However, the battalion was ambushed by the Japanese rearguard just as it reached the coconut grove, and by nightfall the forward elements had taken heavy casualties and been compelled to fall back. On the following morning, the marines called in air attacks and brought up a platoon of tanks to support their advance. The advance soon dissolved into confusion, with some of the tanks mistakenly firing on friendly positions, but by a time late in the afternoon the marines had secured the coconut grove.

With the grove secured, the marines rapidly expanded their perimeter, reaching Line 'Dog' on 15 November. By this time there were 33,861 men and 23,137 tons of supplies in what was now a secure lodgement, and the 'Seabees' were pressing ahead with all speed to build a road network within the lodgement. On 16 November the first road was completed across the perimeter, and completion of the airfield could begin in earnest. However, on 17 November Japanese aircraft finally inflicted a serious blow against the Americans, sinking destroyer transport McKean with heavy loss of life.

The initial ground campaign came to an end on 25 November, when the marines completed the destruction of the 23^rd Regiment under the command of Major General Shun Iwasa’s 65^th Brigade at Piva Forks. The encounter had started on 17 November, when a marine patrol discovered and occupied an unoccupied roadblock on the Numa Numa Trail leading to the north from the Piva area. The Japanese attempted to reoccupy to the roadblock on 18 November and were ambushed by the marines, suffering heavy casualties, one of them an officer carrying documents of considerable intelligence value. Over the next two days, the marines secured this part of the perimeter and sent out patrols, which encountered isolated Japanese rearguards and fought some sharp actions.

On 21 November, the 3^rd Raider Battalion spearheaded an advance along the East-West Trail from the point where it branched from the Numa Numa Trail. The men of this battalion crossed the crest of the trail to discover that they were looking down on the main Japanese positions to the east of the Piva river and astride the East-West Trail. The position also cut the Japanese supply line to the west. The marines dug in as rapidly as possible before Japanese mortars could register on the position, losing seven men killed but holding the position. On the following day the 2^nd Raider Battalion relieved the 3^rd Raider Battalion on the crest of the East-West Trail, and the rest of 3^rd Marine Division moved up to Line 'Easy' as the 37^th Division took over much of the lodgement’s northern perimeter.

Meanwhile, on 20 November, the 2/3^rd Marines had spotted a ridge and, recognising the importance of this high ground, the battalion commander immediately ordered one of his platoons to occupy the ridge. During the following morning the marines on the ridge discovered that the Japanese had prepared the ridge for defence, but had pulled out for the night to avoid US artillery fire. When they tried to move back into their positions, the Japanese were met by a deluge of US fire. The platoon commander, Steve Cibik (for whom the ridge was later named), called for mortar support, and two 60-mm (2.36-in) weapons soon arrived. Over the next two days, the Japanese engaged in mortar duels with the marines while attempting to storm the ridge, but failed to dislodge the marines. The marines had thus secured a crucial position on high ground overlooking the battlefield.

The 2/3^rd Marines now undertook a reconnaissance in force to the east, only to discover that the Japanese had constructed a strong defensive line of about 20 pillboxes, and that the 23^rd Regiment was massing for a counterattack. The marines disengaged with some difficulty and moved back behind the perimeter, only to be turned around and thrown back into the line to help repel the Japanese counterattack. On 21 November, the Japanese attempted a double envelopment of the 1/3^rd Marines, but were repulsed by machine gun fire and suffered heavy casualties.

The next two days were spent in preparation for an attack on the 23^rd Regiment, which was estimated to have between 1,200 and 1,500 men. The 37^th Division reached its final planned defensive line, Line 'How', while the 3^rd Marines assembled the required assault force and registered its supporting artillery on known Japanese positions. The marines had noted that the Japanese defences were located parallel with the mountains to the north and were oriented to the south, leaving them vulnerable to an advance from the west.

The attack began on 24 November with what was, so far, the heaviest marine artillery bombardment of the war, in which 5,760 rounds were fired in 23 minutes. However, the Japanese had also registered their artillery, and as the marines were moving up to their line of departure, a Japanese battery twice walked its fire up and down the assembling marines. The battery was spotted and silenced by marine counter-battery fire, but not before it had inflicted the heaviest US casualties of the campaign. However, the Japanese had also suffered heavily from marine artillery, and the marines were able to move forward about 500 yards (455 m) before the Japanese rallied and counterattacked the marine flank. The marines met the counterattack head on and destroyed the Japanese flanking force. By the time the marines reached their objective, after an advance of 1,150 yards (1050 m), all Japanese resistance to their front had ceased.

On 24 November, the 1/9^th Marines attacked to the north-east from Cibik Ridge, soon coming under heavy fire from a parallel ridge to which the marines gave the nickname Grenade Hill. Fighting was at such close quarters that the mortars on Cibik Ridge were unable to fire in support. However, on the morning of 26 November, the marines found that the Japanese had abandoned Grenade Hill. The 23^rd Regiment had been shattered, and had lost at least 1,196 men killed. The marine casualties were 115 dead and wounded. There were to be no more major Japanese attacks on the US perimeter until March 1944, though the Japanese made frequent night air raids. Meanwhile the perimeter was wired and roadblocks established on all routes into the perimeter.

When it appeared that the Americans would hold be able to hold and expand their positions on Bougainville, some elements of the Japanese leadership began to fear that the next US move would be a landing on Buka, the small island just off the north-western tip of Bougainville. This had an airfield which, the Japanese feared, could become the springboard for continued Allied advance, in this instance out of the Solomon islands group and onto the southern coast of New Britain or the south-eastern tip of New Ireland. The Japanese navy’s position was that Bougainville would not be a stepping stone of this type, but would be permanently held by the Allies, while the Japanese army insisted that Buka was the real objective.

The army prevailed and consequently determined that the navy should run in a convoy of some 900 soldiers to Buka, while evacuating 700 aviation personnel, for constant bombing of Buka airfield had left it unserviceable since 1 November. So once again the navy agreed to create a destroyer transport force to allow the implementation of the army’s strategic thinking, and this convoy sailed on 25 November as the last 'Tokyo Express' operation. Under the command of Captain Kiyoto Kagawa, this Buka Reinforcement Unit comprised the destroyers Amagiri, Yugiri and Uzuki carrying troops, and the destroyers Onami and Makinami to escort them.

Alerted to the Japanese movement by air reconnaissance, Halsey despatched two divisions of Captain Arleigh Burke’s Destroyer Squadron 23 to intercept the Buka Reinforcement Unit: this US force comprised Destroyer Division 45 (Charles Ausburne, Claxton and Dyson) under Burke’s direct command, and Destroyer Division 46 (Converse and Spence) under the command of Commander B. L. Austin, and the resulting engagement on 25 November was the 'Battle of Cape St George', so named for the extreme southern tip of New Ireland, and this was the last naval battle of the Solomon islands campaign.

Amagiri, Uzuki and Yugiri landed their troops at Buka, took on the aviation personnel, and headed home at 00.45. But the two-destroyer screen was already running into trouble. The two US destroyer divisions were guarding the western entrance to the St George Channel. If an interception was made, Destroyer Division 45 could make a torpedo attack, covered by Destroyer Division 46, and then the two could reverse roles. The US ships gained radar contact at 01.41, the Japanese ships spotted being the two escorting destroyers. Onami and Makinami were on the starboard side of Amagiri, Yugiri and Uzuki, headed to the west and well in advance of the transport destroyers. Charles Ausburne, Claxton and Dyson were the starboard column, and headed to the north, with Converse and Spence following off Destroyer Division 45’s port quarter.

At 01.45 Destroyer Division 45 turned directly to the east to close and attack the Japanese destroyers. At 01.56 the three US destroyers launched torpedoes for a 4,500-yard (4115-m) run, and then turned to the south. Onami spotted the retiring destroyers at 02.00, but 30 seconds later was hit by several torpedoes and sank almost immediately. Makinami also took hits but remained afloat.

At that moment Destroyer Division 45’s radar picked up the transport destroyers, 13,000 yards (11885 m) from their disintegrated screen. The transport destroyers then turned to the north at maximum speed, hotly pursued by Destroyer Division 45. Yugiri launched torpedoes, but to no avail. Destroyer Division 45 opened fire at 02.22 with the bow guns of all three ships, and the Japanese destroyer transports returned fire, each side scoring near misses. At 02.25 the three transport destroyers separated, each veering off on a separate course 45° apart, leaving Burke a choice of which to pursue. He chose Yugiri, which was hit with gunfire at 03.05. But Yugiri did not give up easily: she circled to face her attackers, and kept on firing her guns and launching torpedoes until she sank under the continued pounding at 03.28. Meanwhile, Destroyer Division 46 had finished off Makinami. Burke then tried to engage Amagiri and Uzuki in a stern chase, but his efforts were in vain. The US group retired at 04.04, and Amagiri and Uzuki survived.

Thus the battle, in which five US destroyers had confronted an equal number of Japanese destroyers, was a resounding American tactical victory inasmuch as Burke’s force had suffered neither damage nor casualties, but had sunk three Japanese destroyers with the loss of 647 men including Kagawa, and damaged another destroyer.

Probably no one realised the fact at the time, but this was the last surface battle (of which the first had occurred at Savo island on 9 August 1942) fought in the Solomon islands group. There had been 15 battles, 12 of them nocturnal surface ship contests. Because of the spectacular nature of carrier battles, many have regarded the Pacific war as a carrier war, but most of the battles, especially those fought in the waters of the Solomon islands, were surface fights by night. The Japanese drew or won at least 10 of these night struggles, but in doing so they reduced their destroyer and, to some degree, their cruiser strengths to the point at which they had to become more conservative.

In reality, the power of the Japanese navy, especially its indispensable destroyer strength, had been broken, while the strength of the US Navy was increasing at an accelerating rate. The nature of the war at sea changed after 25 November. The Japanese navy now surely faced ultimate defeat, short of victory in a decisive battle, which never occurred. At this point Japanese strategic planning began to lose touch with reality, and became increasingly obsessed with fighting and winning an illusory, and indeed impossible, 'decisive victory'.

On the island of Bougainville, meanwhile, in the period 9/19 November the I Marine Amphibious Corps landed the remaining regiment of the 3^rd Marine Division and the US Army’s 37^th Division, which gave the corps the strength it needed to expand its beach-head into a more useful lodgement. Extended and generally very savage combat then followed in the jungle of Bougainville, and the casualty list came to include as many men incapacitated by malaria and other endemic tropical diseases as by combat. With the exception of patrol skirmishes, all of the major combat to enlarge the beach-head inland into a lodgement occurred in the marine sector, where the battles included those known as the Koiari Raid, Piva Trail, Coconut Grove and Piva Forks.

The 36^th Naval Construction Battalion reached Bougainville on 26 November, just as the Piva area was secured, and began work on the inland bomber strip, Piva Uncle.

On 27 November, Geiger ordered the 1^st Marine Parachute Battalion and a company of the 3^rd Marine Raider Battalion to conduct a seaborne raid into the Japanese rear to disrupt the Japanese line communications and also to collect intelligence. Little was known about Japanese positions in the area, and when the raiding force came ashore to the north-west of Koiari early in the morning of 29 November, the 3^rd Marine Raider Battalion company was met by only one Japanese officer armed merely with a sword, who was apparently expecting the arrival of a Japanese force. The marines had landed almost on top of a Japanese supply dump, came under heavy Japanese fire and had to withdraw under covering fire from three destroyers and 155-mm (6.1-in) artillery in the main Cape Torokina lodgement. The dump was left intact and the marines suffered 15 killed and 95 wounded, though they claimed to have killed 145 Japanese.

In November and December the Japanese 23^rd Regiment had emplaced field artillery on the high ground around the lodgement, concentrated in a group of hills along the Torokina river overlooking the south-eastern perimeter. These guns shelled the lodgement, concentrating their fire on the airstrips and supply dumps. The 3^rd Marine Division therefore embarked on the process of extending its lines to enlarge the perimeter and thereby include these hills in a series of operations which lasted through the period 9/27 December.

Early in December, as part of this process, Turnage decided to strengthen the 3^rd Marine Division’s front by occupying the high ground just to the west of the Torokina river. The most southerly part of this high ground, Hill 600, was occupied without difficulty, but the marines moving onto Hill 1000 discovered abandoned Japanese fortifications on the eastern spur of the hill. This feature, dubbed Hellzapoppin Ridge, was a natural fortress 300 ft (90 m) long, with steep slopes and a narrow crest that overlooked much of the lodgement. Here the Japanese had constructed extensive positions on the reverse slopes using natural and artificial camouflage. A patrol was sent to occupy the position on 8 December came under heavy fire from Japanese troops who had reoccupied the position.

Hellzapoppin Ridge proved to be a strong natural fortress, with almost vertical slopes on two sides and heavy forest cover that foiled observation for artillery or air strikes. The Japanese were deeply dug in among the tree roots and had their entire perimeter covered by automatic weapons, leaving no flank to turn. The marines made a succession of frontal attacks, but all were driven back. On 14/15 December a series of TBF sorties attempted to bomb the Japanese out of their position, but the initial attacks with contact-fused bombs achieved little other than strip away some of the vegetation. On 18 December, a final flight of six TBF aircraft with 48 100-lb (45-kg) delay-fused bombs carried out their attacks individually, deliberately and in careful co-ordination with the artillery and infantry, and this finally broke the back of the Japanese defence. The marines lost 12 killed and 23 wounded, and discovered more than 50 Japanese bodies in the area.

On 22 December an infantry and heavy machine gun platoon moved out to occupy Hill 600A, to the east of Helzapoppin Ridge and on the west bank of the Torokina river. This was the highest terrain for a considerable distance to the south and east, and the attacking marines soon came under fire from Japanese troops who had moved onto the hill during the night and dug in on the reverse slope. The two marine platoons were soon reinforced with their entire parent company, but the company commander unwisely attempted a double envelopment of the Japanese without adequate reconnaissance. The whole company came under heavy fire and had to retreat. The next day a second company attempted to feel out the Japanese positions but, despite artillery support, was also driven back. During the morning of the following day, marine patrols found that the Japanese had decamped.

On 15 December 1943, Major General Oscar W. Griswold, commander of the XIV Corps, had relieved Geiger, and Hodge’s Americal Division began to replace Turnage’s 3^rd Marine Division on the perimeter. Thus two army divisions, with strong artillery support, came to be the defence of a lodgement which included a small naval base, three airfields, and extensive supply installations.

On 27 December 1943, Merrill took his cruisers and destroyers to bombard Kieta and to try to lure the Japanese out for a fight and, though the Japanese would not be lured, the US warships bombarded Kieta so severely that it was no longer used as a supply base.

Construction of the coastal fighter strip had been completed by 10 December 1943, although the first aeroplane to use the airstrip, a damaged SBD making an emergency landing, landed on the incomplete strip on 24 November. On 10 December the 77^th Naval Construction Battalion arrived on Bougainville and started work on a second fighter strip, Piva Yoke, parallel with the inland bomber strip, Piva Uncle. Completed on 25 December, the bomber airstrip eventually had three taxiways with 35 hardstands, extensive repair and maintenance facilities, and camp facilities for 7,000 ground personnel.

A base for PT-boats was also completed on Puruata Island, with berths for 18 PT-boats and tank landing ships.

By the end of 1943, with the perimeter secured and the bomber and fighter strips completed, the first phase of the Bougainville campaign had been completed. The Americal Division had taken over the eastern side of the perimeter from the 3^rd Marine Division, and the marines' VMF-216 and USAAF’s 70^th Fighter Squadron were operating out of the airfield. Allied intelligence reported that the Japanese in the northern part of Bougainville were digging in around the airfields on Buka and at Bonis, on the mainland of Bougainville opposite Buka island, and were unlikely to move against the US lodgement. The chief threat was thought to be from the south, where some 11,000 men of the 6^th Division might move against the lodgement using trails well concealed against air reconnaissance by the jungle canopy.

The Americans carefully prepared the perimeter, building extensive chains of pillboxes and other fortifications, laying out barbed wire and booby traps, clearing extensive fields of fire, and installing searchlights. Meanwhile the US forces patrolled aggressively outside the perimeter, where there were clear signs of increasing Japanese activity by February 1944.

One particularly celebrated patrol was that of the 1/Fiji Regiment, which moved out of the perimeter on 28 December and along the Numa Numa Trail to Ibu with the object then of fanning out and reporting on Japanese activities on the east coast of Bougainville. Supply was by air drop. The patrol reached Ibu on 2 January, hacked out an airstrip for Piper L-4 single-engined observation aircraft, engaged in a number of firefights with Japanese patrols, and was attacked by a major Japanese force of 14 February. The patrol fought an expert rearguard action back to the perimeter, arriving 19 February and claiming 120 Japanese killed in exchange for one Fijian slightly wounded.

On 27 February the Americans occupied the two Magine islets, in the centre of Empress Augusta Bay’s coast just to the east of the mouth of the Torokina river, in order to prevent their use by the
Japanese to observe the US beach activity and also as a US observation post for for the observation of Japanese activities to the east of the Torokina river.

Hyakutake had finally and somewhat belatedly become fully cognisant of the acute reality of his situation. He sent his main ground forces, centred on the 6^th Division, on a notably arduous approach march through the jungle to attack the Cape Torokina perimeter. These forces were not able to finish their assembly outside the US perimeter and launch their 'Ta' attack until 7 March, and by that time the 37^th Division was well entrenched and fully alert to the coming attack as a result of the interrogation of prisoners.

The Japanese plan was overly complex, as were many of the Japanese plans of World War II. This in effect negated the Japanese superiority in numbers, ability to move under jungle cover, and possession of high ground overlooking the US perimeter, which might otherwise have been used as the basis for a single concentrated attack which, delivered at the right point, might have posed a serious threat to the US lodgement. Hyakutake erred significantly, however, in making the assumption that his force faced one division, whereas it was of course two divisions. Hyakutake was so confident that the 15,000 men he committed to the attack would break though the US perimeter that he had already planned the surrender ceremony, to take place on 17 March. The Japanese troops were therefore issued with rations for just two weeks. Hyakutake believing that the men would then be able to feast on captured US rations.

Local command of the offensive was given to Kanda, commander of the 6^th Division, who was also given two battalions of the 53^rd Regiment and part of the 81^st Regiment. Kanda divided his force into three columns. The first column was led by Iwasa, the commander of the 6^th Division's infantry group, and comprised the 23^rd Regiment, one battalion of the 13^th Regiment and supporting elements, totalling some 4,150 men. Its objective was Hill 700 on the right flank of the 37^th Division. From this position the Japanese hoped to drive down onto the Piva airfields. The second column was centred on the 4,300 men of the 45^th Regiment and led by the regimental commander, Colonel Isashi Magata. This was to attack across the low ground to the west of Hill 700 and join the assault on the airfields. The 1,350-man third column comprised two battalions of the 13^th Regiment and one company of engineers under the command of Colonel Toyhorel Muda, and was to take Hills 260 and 309, then move forward to Hill 608 and secure Iwasa’s flank.

The Japanese had spent most of January and February improvising a road from Mosigetta to the their planned assembly area in the hills to the north of Torokina. The attack, originally scheduled for 6 March, had to be postponed to 8 March as a result of delays in getting the troops in place. The Japanese offensive finally began with an artillery duel in which the Japanese forced the aircraft on the Piva strips to evacuate to Guadalcanal, but otherwise did little damage, while the US guns were supplemented by 56 SBD dive-bombers and 36 TBF bombers which struck the Japanese at Hill 1111.

The Americans were thoroughly alerted, while the Japanese infantry had not yet arrived at the US perimeter in force.

Hill 700 comprises two high points separated by a saddle, with almost all its approaches characterised by 65° to 70° slopes. Beightler did not anticipate an attack on so commanding a position, and the hill was held by just two infantry companies and a heavy weapons company of the 2/145^th Infantry, albeit well dug in. Shortly after midnight on 9 March, in a torrential tropical downpour, the 2/23^rd Regiment attacked the hill and the area to its west, but was driven off. Two hours later, Iwasa launched his main attack, committing the 2/23^rd Regiment and 3/23^rd Regiment against the saddle. The following 3/23^rd Regiment was destroyed by US artillery fire, but the leading wave of the 2/23^rd Regiment reached the US positions, blew apart the barbed wire barriers with bangalore torpedoes, destroyed a pillbox, and secured a lodgement. By dawn the Japanese had a penetration 70 yards (65 m) wide and 50 yards (45 m) deep, which they continued to expand until 12.00, in the process taking seven pillboxes and bringing up heavy weapons with which to interdict the US supply route to the south of the hill. Beightler committed the 1/145^th Infantry in an effort to contain the Japanese, but it took another three days and powerful artillery support for the Americans to drive the Japanese off the hill and restore the position. By then Beightler had been forced to commit a second battalion, the 2/148^th Infantry and the commanding officer of the 145^th Infantry had succumbed to combat fatigue. The battle cost the Americans 78 men killed, while at least 309 Japanese corpses were found in the area.

Meanwhile, at dawn on 10 March, the column led by Muda had struck against Hill 260, which accommodated a small observation post of the 2/182^th Infantry well outside the main US perimeter. Despite the value of the observation platform built high in a banyan tree, the staff of Americal Division were surprised when Griswold ordered the position to be held. By then the Japanese had already overrun most of the US positions, which were concentrated on the hill’s southern peak (the South Knob). The Americans occupied the hill’s northern peak (North Knob) but could not dislodge the Japanese, although US artillery destroyed the banyan tree in which the observation platform had been nested. The Americans halted their attempts to recapture the South Knob on 20 March, leaving the position to be battered by artillery and contained by patrols, and on 28 March a patrol discovered that the Japanese had withdrawn. The struggle cost Americal Division 98 dead and 581 wounded, while some 560 Japanese dead were counted around the position.

Magata’s column was slow to begin its attack, which was unfortunate for the Japanese as the terrain in this sector was flat and favoured the attackers. The Americans had captured documents revealing Magata’s intentions, and the defending 129^th Infantry had spent the previous two months building a formidable defence line based on mutually supporting pillboxes protected by double-apron barbed wire barriers and minefields, and equipped with numerous machine guns, 75-mm (2.95-in) pack howitzers and 37-mm anti-tank guns well supplied with canister anti-personnel rounds. At 16.00 on 11 March, the commander of the 129^th Infantry ordered his outposts to fall back to the line of pillboxes, and the divisional artillery pounded the area in front of the 2/129^th Infantry for 10 minutes. After dusk a firefight broke out in which the Americans were careful not to reveal their pillbox positions but were unable to prevent Japanese infiltrators from cutting gaps in the barbed wire. Magata committed two battalions at the break of day, and by sheer weight of numbers captured seven pillboxes. The 1/129^th Infantry was brought up from reserve and recaptured two of the pillboxes, and that evening searchlights illuminated the low cloud cover to create 'artificial moonlight', while automatic fire was poured into the Japanese positions. On the following day, Sherman medium tanks of the 754^th Tank Battalion were committed to the fight, and by 14 March the US position had been restored. Another attack by Magata shortly before dawn on 15 March took a single pillbox before being contained and driven back with the aid of tanks and an attack by 36 aircraft. A third Japanese attack on 16 March made little progress. This final attack cost the Japanese 194 dead and one man taken prisoner, and the Americans two dead and 63 wounded.

Kanda now withdrew his assault forces to regroup, assembling the survivors to make a final attempt to break through the 129^th Infantry. In the five-day period which followed, the Americans rebuilt damaged positions and buried the Japanese dead. Meanwhile Allied codebreakers had decrypted an intercepted message from Hyakutake to Imperial General Headquarters detailing his plan to attack on 23 March. The intercepted message was rushed to Griswold, who was already dealing with a preliminary assault which had seized a low ridge very close to the battalion command post of the 2/129^th Infantry. The Japanese penetration was driven back by tanks and infantry on 24 March, and shortly after 12.00 the Japanese assembly areas opposite the 129^th Infantry were hit by the most massive artillery barrage of the Pacific War up to that time, no fewer than 14,882 shells falling on the Japanese from seven battalions of heavy and medium artillery, plus the mortars of the 37^th Division. Two days later the Japanese remnants started to fall back toward their base at Buin. The casualties in the Battle of the Perimeter included 263 Americans killed and about 5,500 Japanese dead.

A notable factor in the crushing defeat which the Japanese had suffered was the poor physical condition of their men. US medical personnel who examined Japanese prisoners of war and Japanese dead concluded that 90% of the Japanese troops were already suffering from malnutrition, malaria, beri-beri, or other debilitating illnesses.

After the end of the Battle of the Perimeter, Griswold had come to the conclusion, supported by his superiors, that the Japanese on Bougainville could no longer have any influence on the outcome of the war, and therefore instructed his divisional commanders to engage in nothing more than aggressive patrolling.

On 5 April 1944, after establishing patrol sweeps along Empress Augusta Bay, the Americal Division’s 132^nd Infantry launched a successful attack to capture the Japanese-held village of Mavavia. Two days later, while continuing a sweep for Japanese forces, the regiment encountered prepared defences and destroyed about 20 Japanese pillboxes using pole charges and bazookas. Later, the 132^nd Infantry, together with elements of the Fiji Regiment, was entrusted with the task of securing the heights to the west of the Saua river. The Americans and Fijians captured Hills 155, 165, 500, and 501 in fierce fighting that lasted until 18 April, when the last of the Japanese defenders were killed or driven off.

From 28 March the Americans were reinforced by combat elements of Major General Raymond G. Lehmann’s 93^rd Division, which was the first African American infantry formation to see action in World War II.

The Allies concentrated on the construction and expansion of several airfields in the lodgement, and from these undertook bomber and fighter operations over Rabaul, Kavieng and other Japanese-held bases in the South-West Pacific area. Air support over Bougainville was provided largely by squadrons of the Royal New Zealand Air Force, US Marine Corps and US Army Air Forces under the control of the Air Solomons command.

After studying surviving Japanese records, Australian intelligence officers later estimated that 8,200 Japanese troops were killed in combat during the US phase of operations, and 16,600 more died of disease or malnutrition.

The Japanese were completely cut off from resupply, and by April 1944 their rice ration was cut to 8.8 oz (250 grams) per day. The rice supply was totally exhausted in September, and most of Hyakutake’s men were put to work on 'garden' (vegetable growing) plots. Allied pilots took to dropping napalm on these Japanese gardens, and Japanese morale plummeted to the point where desertion was common and there was real danger of mutiny. With Japanese morale at its lowest ebb, and the US forces ordered not to stir up trouble pointlessly, an unspoken truce settled over the perimeter.

From October 1944 the US XIV Corps was gradually withdrawn to be readied for involvement in the 'Mike I' invasion of Luzon in the Philippine islands group, and the Bougainville lodgement was taken over by Lieutenant General Stanley G. Savige’s Australian II Corps. This comprised Major General W. Bridgeford’s Australian 3^rd Division (Brigadier J. Field’s 7^th Brigade, Brigadier H. H. Hammer’s 15^th Brigade and Brigadier R. F. Monaghan’s 29^th Brigade), together with two independent brigades in the form of Brigadier J. R. Stevenson’s 11^th Brigade and Brigadier A. W. Potts’s 23^rd Brigade detached from Major General E. J. Milford’s Australian 5^th Division. The 23^rd Brigade was used mainly to garrison outlying islands. Savige assumed command of the lodgement on 22 November, and by 12 December all US units had been pulled out of the line.

General Sir Thomas Blamey, the commander of the Australian Land Forces, and Savige elected to take the war to the Japanese rather than sit idly in the perimeter. The reasons for this controversial decision remain obscure. However, MacArthur had all but shut the Australian army out of the counter-offensive against Japan, relegating Australian units to secondary operations and garrison duty, and it is probably that Blamey wished to rebuild the Australian army’s reputation as a first-rate fighting force.

Allied intelligence estimates of the remaining Japanese strength on the island varied at the time, although it was believed that there were around 17,500 Japanese on Bougainville. Although this was later proved to be a major underestimate, the Australians nevertheless believed that the Japanese formations in the area, while understrength and almost totally devoid of heavier weapons (or at least the ammunition for them), were still capable of carrying out effective combat operations. The Japanese forces still capable of combat included Kanda’s 6^th Division and Major General Kesao Kijima’s 38^th Independent Mixed Brigade. As a result, it was decided that the II Corps would go on the offensive in order to clear the Japanese from the island by means of a three-pronged campaign in the northern, central and southern sectors of the island.

The 3^rd Division was supported by a number of artillery units including the 2^nd and 4^th Field Regiments and the 2^nd Mountain Battery, and various anti-aircraft units. Later, U Heavy Battery, with four 155-mm (6.1-in) howitzers, was transferred from Lae in North-East New Guinea, as was the 2/11^th Field Regiment. It was decided, in order to provide organic fire support during the advances, that divisional artillery elements would be allocated to the units they were supporting. At the outset, the 3^rd Division’s engineer complement was just the 5^th and 11^th Field Companies, but later in the campaign other engineer assets arrived, these including the 7^th, 10^th and 15^th Field Companies; the last of these, the 7^th Field Company, arrive in June 1945. Ultimately the division had almost 1,600 engineers in five field companies and various supporting plant, park and other units. This represented one of the largest engineer contingents within an Australian division during the war.

The 3^rd Division was deployed without armoured support, but in December 1944 B Squadron of the 2/4^th Armoured Regiment, equipped with Matilda II infantry tanks, arrived and then took part in operations.

By the time Savige ordered a general offensive on 23 December, the Australians had already made several strong probes into Japanese-held territory. Savige knew his force was probably outnumbered, but he was counting on the poor morale and dismal physical condition of the Japanese to tip the balance. By this time, in fact, the Japanese were dying of illness and starvation at the rate of some 3,000 men every month.

The 7^th Brigade, supported by the 2^nd Field Regiment, was the first Australian unit to enter combat on Bougainville when its 9^th Battalion launched a surprise attack in the central sector of the island on a Japanese outpost at Little George Hill on 25 December. In the next month the battalion seized control of Artillery Hill, while the 29^th Brigade began patrolling operations in the southern sector.

The southern offensive began with an attack on Pearl Ridge, on the track between Torokina and Numa Numa, by the 25^th Battalion on 30 December. In two days this drove 500 defenders off a strong position from which the Australians could observe both coasts of the island. The Australians then installed a 3,000-ft (900-m) cable to the ridge and used it to pull a bulldozer to the top to begin construction of a road, and the ridge became a major patrol base commanding the central part of the island.

The capture of Pearl Ridge in the central sector, on the trail between Torokina and Numa Numa, by the 25^th Battalion, was an undertaking which effectively divided the Japanese forces in the northern and southern ends of the island, gave the Australians control of north-east/south-west communications and protection against further counterattacks, and also opened the way for a drive to the east coast. The 3^rd Division then refocused its attentions onto the northern and southern sectors. The independent 11^th Brigade assumed control of the drive to the north, while the 3^rd Division concentrated on the drive to the south in the direction of Buin, where the Japanese main strength was known to be concentrated.

In the north the 11^th Brigade, supported by elements of the Fiji Regiment, advanced along the coast toward the Genga river and despatched patrols inland to flush the Japanese off the higher ground. The advance was rapid until 19 January, when patrols discovered that the Japanese were holding strong dug-in positions on Tsimba Ridge. Savige was reluctant to commit his tanks, and took until 6 February to secure the final dislodgement of the Japanese from this feature. On 26 March a combined ground attack and amphibious landing forced the Japanese out of Soraken Point and into the Bonis peninsula. Here the Australians encountered formidable Japanese defences, however.

In the north the 11^th Brigade was almost spent. An attempt to flank the Japanese lines with an amphibious landing on 8 June at Porton Plantation nearly ended in disaster, and the Australians made no further attempt to clear the Bonis peninsula during the remaining weeks of the war.

Deciding instead merely to contain the Japanese along the front in the area of Ratsua, Savige thereby made it possible for greater strength to be switched to the southern sector for the drive toward Buin.

On the east coast, the 1,000-man garrison at Kieta was contained by guerrilla forces, which controlled much of central Bougainville and claimed to have killed more than 2,000 Japanese by the end of the war.

Rotating his brigades, Bridgeford meanwhile advanced to the south from Torokina in the direction of the Puriata river. After the Australians had crossed this, they met their first serious resistance on the Hupai river on 10 January. Here the Australians were forced to bring up anti-tank guns to clear a line of pillboxes. The Australians then rapidly advanced to more open terrain and on 11 February seized Mosigetta. Anticipating more serious resistance farther to the south, Savige committed his tanks on 17 March, and on 19 March the 25^th Battalion cleared a system of pillboxes on its line of advance. Warned by intelligence that Kanda was about to launch a major counterattack, the Australians dug in around a terrain feature dubbed Slater’s Knoll. Two Japanese probing attacks on 27 March were followed by the main assault on 30 March, and this struck a single Australian company to the south of the knoll. The Australians beat off four bayonet charges, but only 16 Australians in the position were left unwounded, and the line was pulled back to the knoll. The counterattack had itself by 5 April, when waves of Japanese charged into massed automatic weapons fire and artillery barrages. Out of a force consisting of 2,400 of Kanda’s freshest troops, at least 620 were killed and another 1000 wounded. Thereafter Kanda reverted to a purely defensive strategy and began moving troops from the Shortland islands group to Buin.

In this same month the the 15^th Brigade took over from the 7^th Brigade and resumed the advance on the Hongorai, Hari, Mobai and Mivo rivers. Early in July, the 29^th Brigade relieved the 15^th Brigade and continued the advance, and as the brigade attempted to cross the Mivo river, the Japanese launched a ferocious counterattack which fell on the 15^th Battalion, which held its ground with great tenacity and drove back the Japanese attack.

After this, the Australian advance came to a halt as torrential rain turned the axis of advance into a sea of mud and washed away most of the bridges on which the Australian supply system was dependent. As the situation became worse, even patrolling operations had to be stopped. Patrolling was resumed, however, from a time late in July and into August, as isolated pockets of Japanese began to attack the 3^rd Division’s supply lines and support units.

As the Australians prepared to resume their advance, the 'Silverplate' and 'Centerboard' atomic bombings of Hiroshima and Nagasaki combined with the success of the Soviet 'Avgust Buri' invasion of Manchukuo to persuade Japan into an unconditional surrender which brought an end to the fighting on Bougainville on 21 August 1945, by which time the Australians had penned the surviving Japanese forces into an area measuring some 15 by 30 miles (24 by 48 km), so ending this second phase of the Bougainville campaign. The campaign had cost the Australians 516 dead and 1,572 wounded, though it is believed that over the same period the Japanese lost about 8,500 men killed in combat, together with another 9,800 dead from disease and malnutrition. Some 23,571 troops and labourers surrendered at the end of the war.

The Bougainville campaign brought to a close the long struggle up the ladder of the Solomon islands group from Guadalcanal. In conjunction with the efforts of MacArthur’s forces on New Guinea, the successful campaign had isolated and neutralised Rabaul. No less important was the Japanese loss of men and matériel. Thousands of soldiers had been killed or left to die in the Solomon islands group. Even more crushing were the Japanese losses in warships and transport vessels which, at this stage of the war, could not be replaced. And finally, perhaps most significant of all, the great Japanese losses in aircraft and trained pilots were decisive. Japanese naval air power, which had once made the Combined Fleet one of the most effective fighting forces in the history of modern sea power, had now been all but wiped out. Without it, the Japanese would be unable to oppose the great central Pacific offensive that the Americans were now about to launch.

Nor, for that matter, could they mount an effective air defence against MacArthur’s projected drive to retake the Philippines. In this sense, the American victory in the Solomon islands group was strategically as well as operationally decisive, greatly hastening and thereby ensuring Japan’s ultimate defeat.