The ship, now the flagship of Rear Admiral Morikazu Osugi, departed Truk on 30 October for Rabaul just as the Americans were preparing to invade Bougainville Island on 1 November. The Japanese attempted to disrupt the landings on the night of 1/2 November with a force of two heavy cruisers, two light cruisers, including "Agano", and six destroyers under the command of Rear Admiral Sentarō Ōmori. The Japanese ships had been spotted by American aircraft around 21:00 and Task Force 39, which consisted of four light cruisers and eight destroyers, was ordered to intercept them.