Battle off Horaniu

The Battle off Horaniu (Japanese: 第一次ベララベラ海戦) was a minor naval battle of the Pacific campaign of World War II, fought near Vella Lavella in the Solomon Islands. On the night of 17–18 August 1943, four United States Navy destroyers intercepted an Imperial Japanese Navy convoy carrying troops to Horaniu, on the northern coast of Vella Lavella, where they were to establish a barge base to support the movement of troops through the region.

The Japanese convoy was escorted by four destroyers, and both sides exchanged torpedoes and gunfire from long range. After two Japanese destroyers were slightly damaged, the escort withdrew, allowing the U.S. force to sink five small ships from the convoy. However, the majority of the troop-carrying barges escaped by hiding along the Vella Lavella coast and subsequently completed their mission on 19 August. In October, the Japanese used the base to support the mass withdrawal of troops from Kolombangara.

In mid-1943, in the wake of the Guadalcanal campaign, the Allies launched their next offensive in the Solomon Islands, focused upon seizing the major Japanese airstrip at Munda on New Georgia. After the fall of Munda on 4–5 August and defeat in the Battle of Vella Gulf on 6–7 August, the Japanese decided to evacuate their garrisons in the central Solomons, firstly moving to Baanga Island while planning to bring forces south from Rabaul for a potential counterattack.

On 15 August, the Allies landed on Vella Lavella, bypassing the main Japanese troop concentration on Kolombangara. To maintain contact with these troops, and ensure their later withdrawal, the Japanese planned to establish a staging base at Horaniu, on the northern tip of Vella Lavella.

Commanded by Captain Matsuji Ijuin, the destroyers Sazanami, Hamakaze, Isokaze, and Shigure left Rabaul on 17 August to rendezvous with a troop convoy from Buin, on Bougainville. This convoy included 13 barges, four motor torpedo boats, the subchasers Cha-12 and Cha-5, and a Soukoutei-class armored boat. The troops embarked consisted of two Imperial Japanese Army companies and an Imperial Japanese Navy platoon.

After the Japanese force was located by Allied reconnaissance aircraft, Rear Admiral Theodore S. Wilkinson, commander of the Third Amphibious Force, dispatched a division of four destroyers from Purvis Bay on Florida Island to intercept them. This force consisted of USS Nicholas, O'Bannon, Taylor, and Chevalier, under Captain Thomas J. Ryan. They departed their anchorage at 15:27 on 17 August and began a fast run up the New Georgia Sound, also known as "The Slot". When Ryan's destroyers were off the north coast of Kolombangara, lookouts on watch saw a burst of anti-aircraft fire in the distance, giving away the position of the Japanese convoy.

Despite a full moon, visibility was limited to 3 miles (4.8 km) due to low-lying clouds and intermittent rain showers. However, at about 23:30, the Japanese convoy was attacked by eight AirSols Avenger torpedo bombers and forced to scatter, although no ships were damaged. Two of the escorts, Isokaze and Shigure, sailing abreast, began herding the smaller craft back into formation, while Sazanami and Hamakaze continued on a northwesterly course. Ryan was advised by the Avengers the Japanese ships were still heading for Vella Lavella, although his destroyers were detected shortly afterwards by a Japanese reconnaissance aircraft, which began circling in preparation for an attack. The convoy was still reforming when at 00:29 on 18 August Ryan's radar detected the Japanese destroyers to the northwest at a range of 23,000 yards (21,000 m), then the Japanese barges; at 00:32, Japanese lookouts spotted the U.S. destroyers, which had closed to 16,400 yards (15,000 m).

The Japanese convoy was still 16 nautical miles (30 km; 18 mi) short of its destination, and Ijuin was under orders to avoid decisive engagement. He dispatched two of his destroyers to turn to the north in an effort to lure the U.S. force away from the troop-carrying vessels. To conceal his position, Ryan decided not to use his deck guns and began maneuvering for a torpedo attack on the Japanese destroyers, rather than attacking the barges. This surprised Ijuin who had expected the opposite. Around 00:40, the Japanese aircraft dropped several flares over the U.S. ships, giving away their location, and Ryan turned back to engage the convoy to his east. Ijuin ordered his ships to begin firing torpedoes six minutes later, loosing 31 between 00:50 and 00:54 at a range of 12,500 yards (11,400 m). By making a series of turns to avoid the Japanese barges, the American destroyers unintentionally avoided all 31 torpedoes, and around 00:56, the Japanese gunners opened fire. However, to avoid revealing their position their searchlights were turned off, and no damage was inflicted on Ryan's destroyers.