As the skies began to grow overcast, at 01:00 on 13 July, the Allied ships established radar contact about east of the northern tip of Kolombangara at . Ainsworth assumed he had a complete surprise as the Japanese lacked radar, but in reality, the Japanese had been aware of the Allied force for almost two hours. Despite not possessing radar, the Japanese ships had the ability to detect the electric impulses of the Allied radar systems, and from this, the Japanese crews were able to gain an accurate plot of Ainsworth's dispositions. After sighting the Japanese force at 01:03, the U.S. destroyers of McInerney's squadron increased speed to engage the Japanese force with their torpedoes while the cruisers turned to deploy their main batteries and engage to starboard. Unknown to Ainsworth, the Japanese destroyers had already launched Long Lance torpedoes, which had a longer range than the Allied torpedoes. After firing their salvoes between 01:08 and 01:14, the Japanese destroyers turned away to regroup.