 The sister ships then rejoined the Kido Butai at Staring Bay on Celebes Island in preparation for the Indian Ocean raid . By this time the air groups had been reorganized to consist of 21 each of the A6Ms , D3As and B5Ns . The Japanese intent was to defeat the British Eastern Fleet and destroy British airpower in the region in order to secure the flank of their operations in Burma . Shōkaku and Zuikaku contributed aircraft to the 5 April Easter Sunday Raid on Colombo , Ceylon . Although the civilian shipping had been evacuated from Colombo harbor , the Japanese sank an armed merchant cruiser and a destroyer and severely damaged some of the support facilities . The Kido Butai returned to Ceylon four days later and attacked Trincomalee ; the sisters ' aircraft sank a large cargo ship and damaged the monitor HMS Erebus . In the meantime , the Japanese spotted the light carrier HMS Hermes , escorted by the destroyer HMAS Vampire , and every available D3A was launched to attack the ships . Aircraft from Shōkaku and Zuikaku were the first to attack the Allied ships , both of which were sunk . 
