On 14 July, "Mutsu" was transferred to Battleship Division 2 and then to the advance force of the 2nd Fleet on 9 August. Two days later, the ship departed Yokosuka accompanied by the cruisers , , , , , , the seaplane tender and escorting destroyers to support operations during the Guadalcanal Campaign. They arrived at Truk on 17 August. On 20 August, while sailing from Truk to rendezvous with the main body of Vice Admiral Chūichi Nagumo's 3rd Fleet, "Mutsu", the heavy cruiser "Atago", and escorting destroyers unsuccessfully attempted to locate the escort carrier in response to a flying boat detecting the American ship.