The American landings on Guadalcanal and Tulagi on 7 August caught the Japanese by surprise. The next day, "Ryūjō" was transferred to Carrier Division 1 and departed for Truk on 16 August together with the other two carriers of the division, and . Her air group consisted of 24 Zeros and nine B5N2s. Admiral Isoroku Yamamoto, commander-in-chief of the Combined Fleet, ordered Truk to be bypassed and the fleet refueled at sea after an American carrier was spotted near the Solomon Islands on 21 August. At 01:45 on 24 August, Vice Admiral Chūichi Nagumo, commander of the Mobile Force, ordered "Ryūjō" and the heavy cruiser , escorted by two destroyers, detached to move in advance of the troop convoy bound for Guadalcanal and to attack the Allied air base at Henderson Field if no carriers were spotted. This Detached Force was commanded by Rear Admiral Chūichi Hara in "Tone".