Throughout July and into early August, a series of nightly actions took place involving by U.S. destroyers, PT boats and aircraft against the Japanese reinforcement efforts. The most significant action during this time came on the night of 19/20 July, when a force of 11 ships, consisting of cruisers and destroyers under Rear Admiral Shoji Nishimura, was detected by US aircraft in The Slot. At least one destroyer, "Yugure", was sunk, and the cruiser "Kumano" was damaged, while four US aircraft were lost. After this, the Japanese chose to use the Vella Gulf and the Blackett Strait along the western coast of Kolombangara rather than the direct route through the Kula Gulf. This resulted in the Battle of Vella Gulf and Battle off Horaniu in early August. In late September and early October, the Japanese began evacuating their ground troops from Kolombangara. A series of interdiction actions took place during which the U.S. Navy claimed to have sunk 46 barges, killing thousands of Japanese troops. Another action was fought between Japanese and U.S. destroyers off Kolombangara on the night of 2–3 October during which both sides ineffectively exchanged torpedoes and gunfire.