The land battle of Vella Lavella (15 August-7 October 1943) was one of the first examples of the leapfrogging strategy that carried the Americans across the vast distances of the Pacific.
In the aftermath of their defeat on Guadalcanal the Japanese entered the defensive stage of their war plan. Each island base was to be defended fiercely, wearing down the Americans and allowing the next base in the line to be developed. As the Americans struggled to capture Munda (2 July-5 August 1943) on New Georgia, the Japanese used the time to build up the defences of nearby Kolombangara. An American assault on Kolombangara would give them time to improve the defences of Bougainville, the most westerly of the major islands in the Solomon Islands.
The original Allied plan for 1943 would have played into Japanese hands. The aim was to eliminate each Japanese base in the Solomons and on New Guinea, before capturing the key base at Rabaul. The idea of leapfrogging one or more of the Japanese bases had been suggested from the start of 1943, but the first example in practice came in the Aleutian Islands, where the capture of Attu Island forced the Japanese to evacuate the more easterly Kiska Island. Rabaul itself would eventually be bypassed, as would a succession of powerful Japanese bases.
In the Solomons the idea of bypassing Kolombangara was first suggested in mid-July, at a time when the battle for Munda was stalled in the thick jungle. The new target would be the almost undefended island of Vella Lavella, north-west of the New Georgia group. The occupation of this almost undefended island would leave the Japanese base on Kolombangara isolated, and probably force the Japanese to evacuate it.
At this stage the only Japanese troops on Vella Lavella were some survivors of the naval battle of Kula Gulf who had managed to reach land. They were only lightly armed and were badly organised.
The Americans badly needed to scout their new target, and on on 21 July a scouting partly was sent to the island. The group included the Rev A.W.E. Silvester, New Zealand Methodist bishop for New Georgia and Vella Lavalla, and Lt. Henry Josselyn, RAN, a coastwatcher. It landed on the south-eastern coast of the island and spent six days exploring. On their return they reported that the island was undefended, had suitable sites for an airfield and recommended landing in the south-east, at Barakoma.
The first American troops, from a scouting party of 45 men, landed on the island on the night of 12-13 August. The Japanese turned out to be more numerous than expected, so reinforcements were sent by PT boat on 14 August. The main invasion fleet left Guadalcanal on the same day, and by dawn on 15 August the unopposed landings had begun. The first wave of troops, carried on four fast destroyer transports, was ashore by 6.45am.
The second wave, carried on twelve LCIs, took a little longer to unload. Only eight could use the beach at one time, and they were the target of Japanese air raids. Despite these attacks the LCIs were unloaded by 9.15am and the third wave, on the slower LSTs began to unload. The LSTs were also the target of Japanese aircraft, but again none were hit and by the end of 15 August the Americans had a secure foothold on the island, and had landed 4,600 men.
The landing on Vella Lavella took place two days after Japanese Imperial HQ had decided not to send any more troops into the central Solomons. They decided not to try and regain control of Vella Lavella, but instead to establish a barge base at Horainu, on the north-eastern shore, for use by ships heading towards Kolombangara. Two army companies and a platoon of naval troops departed from Bougainville on 17 August. The US Navy attempted to intercept them, but failed (action off Horainu, 18 August 1943), and the Japanese landed safely on 19 August. They now had 390 men at Horainu and at least another 200 stragglers on the island.
The Americans responded to this landing by beginning an advance up the east coast. The first troops moved on 30 August, and by 2 September they had reached Orete Cove, well up the coast. They then began to advance towards the Japanese barge base, encountering sporadic small-scale resistance as they went. On 14 September the Japanese evacuated the base at Horainu, and later on the same day American troops occupied it.
The surviving Japanese troops now began to retreat towards the north-western corner of the island. They were pursued by soldiers from the 14th New Zealand Brigade Group, 3rd Division, under the command of General H.E. Barrowclough. The New Zealanders replaced the Americans from 18 September, and began an advance along both coasts of the island.
By 1 October the Japanese were pinned back into the north-western corner of Vella Lavella. The Japanese decided to evacuate the garrison by sea. The Americans attempted to intervene, but the battle of Vella Lavella (6 October 1943) was a Japanese victory. On the morning of 7 October the last 589 Japanese troops were safely evacuated from the north-western tip of the island.
By this point the Allies had already achieved all of their aims on Vella Lavella. Work on a airfield was well under way by the end of August, and the first aircraft landed on 24 September. Just as expected the capture of Vella Lavella forced the Japanese to abandon Kolombangara. Around 10,000 men were withdrawn by sea, and by 3 October the Japanese were gone. US troops landed on Kolombangara without opposition on 6 October.