 "Shōkaku" and "Zuikaku" joined the "Kido Butai" ("Mobile Unit/Force", the Combined Fleet's main carrier battle group) and participated in Japan's early wartime naval offensives, including Pearl Harbor and the attack on Rabaul in January 1942.In the Indian Ocean raid of March–April 1942, aircraft from "Shōkaku", along with the rest of "Kido Butai", attacked Colombo, Ceylon on 5 April, sinking two ships in harbor and severely damaging support facilities.The task force also found and sank two Royal Navy heavy cruisers, ( and ), on the same day, as well as the aircraft carrier on 9 April off Batticaloa.