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The Battle of Ratsua occurred during the Second World War and involved Australian and Japanese forces. Part of the wider Bougainville Campaign of the Pacific theatre, the battle took place in the northern sector of Bougainville between June and August 1945. Following the failed landing at Porton Plantation in early June, the fighting around Ratsua essentially became a containment action for the Australians as they concentrated their efforts upon driving south towards Buin, which was the main centre of Japanese resistance on the island at the time. As a result, the situation around Ratsua remained largely static until the end of hostilities in mid August.
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After their defeat at Tsimba Ridge[Note 1] in early February 1945, Major General Kesao Kijima—commander of the Japanese 38th Independent Mixed Brigade—[2] had ordered a withdrawal to Numa Numa, leaving a force of 1,400 sailors drawn from the 87th Naval Garrison Force and 2,000 civilians to hold the Bonis Peninsula. Of these civilians, about 600 were armed, although only half were trained to undertake a combat role. As their supplies dwindled, in May–June the Japanese sailors—under the command of Captain Kato, the senior naval officer in Buka—began to raid the Australian supply lines between Ruri Bay and Ratsua as they attempted to hold a position between Porton Plantation and Tarbut.[3] Meanwhile, Australian troops from the 11th Brigade had continued their advance north from Tsimba Ridge in April–May, clearing up to the Soraken Peninsula which was captured by the middle of the month.[4] By the end of May, however, the Japanese fell back behind a series of fortified positions along the base of the Bonis Peninsula, and the Australian advance came to a halt.[5][6]
In an effort to break this resistance and allow the northwards advance to continue, the Australians attempted to outflank the Japanese line of resistance by launching an amphibious landing at Porton Plantation on 8 June.[Note 2] The plan called for a reinforced company from the 31st/51st Battalion to land behind the Japanese positions and attack from the west, while the main force consisting of the remainder of the 31st/51st Battalion and the 26th Battalion attempted to break through from the south.[7] Due to poor planning, inadequate resources and strong Japanese defence, however, the landing failed at considerable cost to Australians,[8] and as their efforts turned towards effecting a withdrawal from the beachhead and rescuing the stranded men, the attempt by the main force to break through from Ratsua also failed as tired troops came up against strong Japanese defensive positions.[9]
Following the failed landing by the Australians at Porton Plantation, the commander of the Australian II Corps, Lieutenant General Stanley Savige, decided to focus the main effort of the Australian campaign upon driving south towards the Japanese garrison at Buin, where the bulk of the Japanese forces were holding out.[10][Note 3] In order to concentrate enough forces for the next phase of the operation, however, Savige decided that the 11th Brigade, which had been carrying the advance north, should be relieved so that it could be transferred to the south following a period of rest and reorganisation.[11]
Nevertheless, there was still a need to maintain the pressure upon the Japanese in the north, and so the 23rd Brigade—which had been previously operating in the central sector after being transferred from garrison duty in the Outer Islands—was also given responsibility for the northern sector as well, relieving the 11th Brigade on 20 June. The brigade's commander—Brigadier Arnold Potts—was charged with keeping the Japanese force bottled up on the Bonis Peninsula and to send out patrols towards the Buka Passage.[12] Initially, Potts was only allowed to allocate one of his three battalions—the 27th—for the task, as the other two—the 7th and 8th Battalions—were to remain in the central sector; however, after intelligence reports indicated that the Japanese forces in the northern sector were stronger than the Australians initially thought, he requested permission to transfer the 8th Battalion, along with a battery of artillery from the 4th Field Regiment that was to be based on the Soraken Peninsula.[12] Due to the requirements of the advance to the south, however, no engineer or armoured support was initially available.[13]
This request was approved, and by 28 June the two battalions and their supporting artillery were assembled; the 8th on the left, or western side of the peninsula, and the 27th on the right, with the artillery based on the Soraken Peninsula.[12] The two battalions sent fighting patrols forward, however, due to the dense terrain, the Australian line of communication was quite long and the infantry spread out over a very wide area—with each battalion occupying a 4,000 yards (3,700 m) front, which was twice the normal standard—security of their rear areas became an issue as the Japanese took the opportunity to disrupt the Australian logistic efforts, conducting ambushes, cutting communications and planting mines along the tracks.[14][15] As the ambushes increased and casualties mounted, forward movement came to a halt, and by 21 July, the 27th Battalion reported having lost 10 men killed and 36 wounded without having gained any ground.[13]
In light of this failure, the Australian brigade commander requested further resources to undertake a full scale offensive aimed at clearing the Japanese from the peninsula. This request was passed up to corps-level, however, there it was denied as Savige could not afford to release assets that were being used in the drive south.[13] Under pressure to keep casualties to a minimum due to criticism in the media in Australia,[11] Potts formulated a plan to withdraw the 27th Battalion from the right flank and to instead concentrate his forces on the left flank along a 3,000 yd (2,700 m) front around the plantation at Buoi, to the north of Ratsua.[13][16] Savige agreed to this on 22 July and the following day the 8th Battalion launched an attack against a feature known to them as "Commo Ridge", where it was believed that the Japanese were attempting to set up a forward position. The attack went in after a preliminary attack from the air, with one company attacking with two Matilda tanks from the 2/4th Armoured Regiment in support. Although the airstrike had been largely ineffective and both of the tanks struggled to cross the "swampy ground", the direct fire support provided by the tanks proved decisive and the Australians took the position within 20 minutes, killing 12 Japanese.[13]
On 24 July, the 8th Battalion launched another attack with two platoons assaulting the Japanese position known as "Base 5". Prior to the assault, over 900 artillery shells and mortar bombs were brought down on the Japanese positions in an effort to prepare the position for the attack, however, this proved ineffective against well entrenched positions.[17] The Australians reached their first objective, which was a small ridge in front of the main Japanese position, however, shortly after they began receiving effective fire from concealed positions which killed two men and wounded another in the forward section, pinning it in place.[17]
Attempts to outflank the bunkers were answered with heavy fire from a medium machine gun and another man was killed and three more wounded. As the attack began to falter, one of the wounded, a 20-year-old private, Frank Partridge, who had been injured in the arm and thigh,[18] braved the heavy fire that was being put down towards him and gathered the Bren light machine gun from the man who had been killed. After pouring suppressing fire onto the bunker, he discarded the Bren and regathered his rifle, before rushing towards the bunker with a grenade and killing its occupants.[4][17] Partridge's actions reinvigorated the attack and allowed the Australians to take the second Japanese position. After the wounded were recovered, however, they withdrew having lost three men killed and five wounded. Against this eight Japanese were confirmed to have been killed.[19] For his actions during the attack on 24 July, Partridge was awarded the Victoria Cross, the British Commonwealth's highest military decoration. He was the last Australian to be awarded the medal during the Second World War, and was also the youngest.[4][20]
Elsewhere, the Australians continued to mount patrols. On 2 August, a patrol from the 27th Battalion was sent out along the Ruri Bay Road in company with two tanks that were to act as their direct fire support. The Japanese were still active in the area, however, and had mined the road with a 500 lb (230 kg) bomb which they had rigged to be detonated remotely. The Australian patrol triggered the device and the resulting explosion killed three men in one of the tanks and wounded eight infantrymen following behind.[13] On 5 August, the Australians reoccupied the position at Base 5 after encountering only slight resistance and subsequently named it "Part Ridge". After exploiting the position, it was discovered that the Japanese had built over 60 bunkers in the area, and subsequently they were withdrawn from the ridge again.[21]
On 11 August, in anticipation of the capitulation of Japan following the dropping of two atomic bombs on Japanese cities, the order to cease offensive combat operations on Bougainville was passed to all Australian units.[21] Three days later, on 15 August, the Japanese Emperor Hirohito publicly announced Japan's unconditional surrender,[22] effectively bringing about an end to the war. On 18 August, in the southern sector of the island the Japanese commander, General Masatane Kanda, dispatched an envoy across the swollen Mivo River to begin negotiations with the Australians for the surrender of the over 23,000 Japanese soldiers left on the island, bringing about an end to the campaign.[4] Throughout the course of the fighting on Bougainville from November 1944 to August 1945, 526 Australians were killed, while a further 1,572 were wounded. It is believed that 8,500 Japanese were killed in action, while a further 9,800 had died from disease during this same period.[21]