三川軍一
During the afternoon of 8 August, a Japanese task force commanded by Vice Admiral Gunichi Mikawa and consisting of five cruisers and a destroyer began to approach the south of Savo Island, with the intention to attack the naval force supporting the landing at Guadalcanal, then those at Tulagi. Anticipating a naval attack following several assaults by land-based Japanese aircraft, the Allied commander of the naval forces, Rear Admiral Victor Crutchley, split his forces around Savo Island: Crutchley aboard HMAS "Australia" led "Canberra", , and the destroyers and on patrol of the southern waters. At 20:45, Crutchley was recalled to meet urgently with US Admiral Richmond K. Turner, overall commander of the amphibious landings. Although "Chicago" was the senior ship after "Australia" departed, "Canberra", which had been following "Australia", found herself at point. Around 01:00 on 9 August, the engines of scoutplanes from Mikawa's ships were heard, but as no warning came from the other groups, it was assumed they were friendly.