Vice Admiral Chuichi Nagumo used five carriers and four battleships in the Indian Ocean raid a naval sortie into the Indian Ocean in April, attacking Allied shipping and bases in the Indian Ocean and the Bay of Bengal. Somerville's fleet was outnumbered and outclassed but he hoped to get close enough to launch a night-time torpedo bomber attack. "Warspite"s fast group set sail to intercept on 4 April, detecting the Japanese attack on the cruisers and and later, a scouting aircraft from the cruiser . The fleets did not meet; "Warspite" withdrew to Addu Atoll and then to Kilindini on the East African coast to protect the convoy routes. The Japanese believed that she was still in Sydney and ordered the Attack on Sydney Harbour.