The Allies had come ashore on Rendova just a week earlier, the opening move of the New Georgia campaign to capture the Japanese airfield at Munda. But Munda could not be taken if the Japanese kept pouring reinforcements across from Kolombangara. The whole strategic equation rested on a simple geographic fact: the narrow water between the two islands, the Kula Gulf, was both the front door for any Japanese resupply run and the killing ground where the U.S. Navy could stop those runs. On the night of 5 July, while U.S. Marines landed at Rice Anchorage to cut the northern supply trail, Rear Admiral Walden L. Ainsworth's Task Group 36.1 was pulling back to resupply when Admiral William Halsey's orders arrived: another Tokyo Express was coming down the Slot from Bougainville, ten Japanese destroyers carrying 2,600 troops toward Vila on Kolombangara's southern tip.

They had already paid a price that night. In the early morning hours of 5 July, the destroyer USS Strong was hit by a Type 93 torpedo fired from 11 nautical miles away by a group of four Japanese destroyers - a range so extreme that American sailors did not initially believe a torpedo could have come from that distance. The Strong broke apart. Forty-six men died. Another 241 were pulled from the water by the destroyer Chevalier while O'Bannon returned fire. The Long Lance torpedo, capable of running 20,000 yards at 45 knots with 1,000 pounds of explosive in its warhead, was the weapon no American planner had expected and no American cruiser or destroyer could easily survive.

Ainsworth's task group, three light cruisers and four destroyers, rounded Visu Visu Point just after midnight on 6 July. An hour later, a few hundred yards off the east coast of Kolombangara and northeast of Waugh Rock, they found Admiral Teruo Akiyama's force in the darkness. The Japanese had divided into units: three destroyers of the support column trailing four destroyers of the 11th Transport Division, with three more destroyers already unloading troops at Vila about 8.5 nautical miles ahead. The American gunners opened fire. Helena's flashless-powder problem immediately turned her into a beacon. Two of Akiyama's destroyers fired torpedoes. The Helena was struck three times, her bow blown off, the rest settling as flame and smoke rolled across the gulf.

Most of the Japanese transport destroyers completed their unloading at Vila. The Nagatsuki ran aground and was abandoned in the morning, later destroyed by American aircraft. Niizuki, carrying Admiral Akiyama himself, was sunk with most of her crew. Amagiri and the others withdrew through Blackett Strait or back through the gulf, with Mochizuki trading fire with the U.S. destroyer Nicholas around 0615 before disappearing behind a smoke screen. The raid was technically a failure for the Japanese - they lost two destroyers and the admiral commanding them - but they had still managed to land 1,600 troops at Vila. More would follow in the days after. What the Americans did next defined the engagement's legacy. The destroyers Radford and Nicholas turned back into the gulf to look for Helena's men in the water, and while they worked, they had to re-engage Japanese destroyers three separate times. They rescued over 750 sailors from the burning oil. Both crews received the Presidential Unit Citation.

One Japanese destroyer escaped from Kula Gulf that night and kept its appointment with history. The Amagiri, heavily damaged but still afloat, withdrew past Kolombangara and returned to the fight. Four weeks later, on 2 August 1943, in the Blackett Strait southwest of Kolombangara, the Amagiri ran down and cut in half a small American torpedo boat whose commander was a 26-year-old lieutenant named John F. Kennedy. The collision killed torpedoman Andrew Jackson Kirksey and motor machinist Harold William Marney. It also set in motion a rescue and a legend that would eventually carry Kennedy to the White House. The escort carrier USS Kula Gulf, commissioned in 1945 and in service intermittently until 1969, was named for this July night - the night the Helena lit herself up with her own gunpowder, and American destroyers went back into fire to save her crew.