Somerville became Commander-in-Chief, Eastern Fleet with his flag in the battleship HMS "Warspite" in March 1942 and was promoted to full admiral on 6 April 1942. Following the fall of Singapore, Somerville transferred his fleet headquarters from Trincomalee in Ceylon to Kilindini in Kenya. In April 1942 Admiral Chūichi Nagumo's powerful 1st Air Fleet (Kidō Butai) centered around five fleet carriers launched the Indian Ocean raid that inflicted heavy losses on Somerville's fleet including a light aircraft carrier, two heavy cruisers, two destroyers, one corvette, five other vessels, and 45 aircraft. The damage inflicted upon Royal Navy and allied Commonwealth forces in the Indian Ocean was nonetheless minimized, being forewarned by intelligence so their heavy units sailed from their bases prior to the Japanese air attacks. Somerville avoided a direct confrontation with the Imperial Japanese Navy, preserving the Eastern Fleet's two fleet carriers and one fast battleship.