 The American landings on Guadalcanal and Tulagi on 7 August 1942 caught the Japanese by surprise . The next day , the light carrier Ryūjō joined the sister ships in the First Carrier Division , which departed for Truk on 16 August . Having learned the lesson taught at Midway , the IJN strengthened the fighter contingent at the expense of the torpedo bombers assigned to its carriers ; the Shōkaku @-@ class carriers mustered 53 Zeros , 51 D3As , 36 B5Ns and 2 Yokosuka <unk> @-@ C " Judy " reconnaissance aircraft between them . After an American carrier was spotted near the Solomon Islands on 21 August , the division was ordered to bypass Truk and continue to the south . Ryūjō was detached early on 24 August to move in advance of the troop convoy bound for Guadalcanal and to attack the American air base at Henderson Field if no carriers were located . The two fleet carriers were to stand off , prepared to attack the Americans if found . 
