The battle that took its name from an obscure cove started because the Japanese needed a back door. Two days earlier, on 15 August, American troops had landed on southeastern Vella Lavella, neatly stepping around the main Japanese troop concentration on Kolombangara. That garrison - some 10,000 men - was now surrounded by American-held water. To reach them later, to feed them, to eventually evacuate them, the Imperial Japanese Navy needed a staging base on Vella Lavella itself. Horaniu on the north coast was the chosen spot. The plan on the night of 17 August was simple enough: four destroyers out of Rabaul under Captain Matsuji Ijuin would meet a convoy of thirteen barges, four motor torpedo boats, two subchasers, and a tender coming up from Buin on Bougainville. The barges carried two companies of Imperial Japanese Army troops and a platoon of Special Naval Landing Force sailors - 390 men total - along with the gear to build the barge depot that would keep Kolombangara alive.

Allied aircraft spotted the Japanese force on the afternoon of 17 August. Rear Admiral Theodore Wilkinson, commanding the Third Amphibious Force from Guadalcanal, did what American commanders in the Solomons had learned to do: he sent destroyers. A division of four - USS Nicholas, Chevalier, O'Bannon, and Taylor under Captain Thomas J. Ryan - slipped anchor at Purvis Bay on Florida Island at 15:27 and ran hard up the New Georgia Sound, the long corridor of water that sailors on both sides called The Slot. The run north took them past Kolombangara. At some point, lookouts watched a distant burst of anti-aircraft fire in the darkness - the Japanese convoy firing at eight TBF Avengers from AirSols that attacked at around 23:30 and forced the convoy to scatter without hitting anything. Ryan now knew roughly where his quarry was. The convoy was still reforming. Japanese escorts Isokaze and Shigure were herding the smaller craft; Sazanami and Hamakaze held a northwesterly course. Ryan pressed the attack.

At 00:29 on 18 August, American radar found the Japanese destroyers at 23,000 yards. Three minutes later Japanese lookouts found the Americans by eye at 16,400 yards. That differential - the ability to see without being seen, by electronics - had transformed Solomons naval warfare over the previous year. What had not changed was the Type 93 Long Lance torpedo, a weapon the Japanese still fired better than anyone else. Both sides loosed weapons at long range. At 00:58 the Americans opened fire with radar-controlled 5-inch guns, landing hits on Hamakaze. Chevalier launched four torpedoes at Shigure from 9,000 yards - they missed. The Japanese laid smokescreens and began to zigzag. Torpedo spreads from Shigure and Isokaze missed in return. An inaccurate radar report suggested another American force approaching from the south. Ijuin had already decided the job his destroyers could do - drawing fire away from the convoy - was done. His escorts withdrew, having lost no ships, having taken only minor damage to two.

With the escort gone, the Americans turned on the convoy and sank what they could find - two subchasers, two motor torpedo boats, and one powered barge. Five small ships went down with an unknown number of personnel killed or injured - men whose names rarely made it into the records, sailors and soldiers who died in dark water a long way from home. But most of the troop-carrying barges were still out there, and the barges were what the Japanese had come to deliver. They did what barges do best in shallow coastal water: they scattered, hid close in to the Vella Lavella shore, used the coastline and the weather to disappear. On 19 August they completed the mission. The base at Horaniu got built. Two months later, in October 1943, Japanese ships used Horaniu as a staging point to evacuate the entire Kolombangara garrison - the mass withdrawal that had been the strategic reason for building the base in the first place. Measured by what it was supposed to prevent, the American intercept off Horaniu was a failure. Measured by what navies can actually do at night in bad weather across miles of black ocean, it was roughly average for 1943.

Hamakaze and Isokaze - the two Japanese destroyers lightly damaged in the action - took part in further operations just three days later. The American destroyers went back to Purvis Bay and were sent out again in other directions, other nights, other convoys. The battle was called a minor action even at the time, tucked between larger engagements like Vella Gulf before it and the naval Battle of Vella Lavella after it. But minor actions added up. Each night in The Slot, ships were expended, men were killed, fuel was burned, and the arithmetic of the campaign ground forward. Below the surface of the Solomons today lie the wrecks of the small craft sunk that night. Far from the famous ships of the war, they remain as reminders that the Pacific War was fought not only at Midway and Leyte but in countless dark hours off unnamed coves, by men trying to steer boats through coastal reefs at flank speed and by their opponents trying to find them in rain.