The Imperial Japanese Navy dispatched Malaya Force (Vice Admiral Jisaburō Ozawa) consisting of the aircraft carrier , six cruisers, a light cruiser and four destroyers on a raid in the northern Bay of Bengal (1–11 April 1942) concurrent with Operation C in April 1942 against British Ceylon (now Sri Lanka) and the Eastern Fleet. The force departed from Mergui (now Myeik, Myanmar) on 1 April.
The Eastern Fleet was far to the south, beyond British Ceylon, operating against the Indian Ocean raid. The British were incapable of defending the merchant ships in the Bay, having only a few aircraft, a couple of Indian sloops and the Greek destroyer . Merchant ships were been ordered to sail in small groups and hug the coast.
On 5 April, Malaya Force divided into three groups to search for targets south of False Point and Cocanada (now Kakinada) in India. On 5 April, aircraft from Ryūjō sank a ship and on 6 April, Calcutta (Kolkata) having ordered ships to disperse on 31 March, cancelled sailings. Aircraft bombed Cocanada and Vizagapatnam (Visakhapatnam) causing minor damage and an exodus. Malaya Force sank 20 merchant ships and damaged three more of over before returning to base on 11 April.
Background
Japanese plan Vice Admiral Jisaburō Ozawa proposed a raid against shipping to and from Calcutta (now Kolkata) at the north end of the Bay of Bengal that would also protect the forthcoming invasion of the Andaman Islands. After the operational order on 9 March for Operation C against Ceylon (now Sri Lanka and the Eastern Fleet, Ozawa suggested that his operation be combined with Operation C. Admiral Nobutake Kondō, the commander of the 2nd Fleet accepted the proposal on 14 March, provided that the Malaya Force stayed in the northern Bay of Bengal and waited east of the 85th meridian east until Operation C had begun, to preserve secrecy.
The attacks of Operation C were planned to begin on 5 April; on 17 March Ozawa issued the orders for Malaya Force to attack Allied shipping in the Bay of Bengal and to sink any Royal Navy and Indian Navy ships that could be found. Beginning on 2 April, most of the force was to depart from Mergui (now Myeik, Myanmar) on the south Burma coast and sail west to the north of the Andaman Islands. In the Bay, at mid-day on 3 April, the 11th Destroyer Division, , , and that were to patrol the waters off Port Blair in the Andaman Islands detached from Malaya Force but the flagship of the 11th Destroyer Division, the light cruiser , would remain with Malaya Force. The Supply Unit () with the tanker and its destroyer escorts and , would also wait near Port Blair. As the 11th Destroyer Division detached, the 20th Destroyer Division, comprising , Ayanami, Shiokaze and was to pass by the Andaman Islands and join Malaya Force.
At 21:00 on 4 April., the force was to reach Point C, 16°N, 86°40′E, where Northern Force, with the heavy cruisers and and the destroyer Shirakumo, would head north during the night to reach Point D, 19°20′N, 87°30′E, at 09:00 on 5 April. If no British ships were waiting in ambush, Northern Force would move to Point E, 18°20′N, 85°E, on the sea lane between Madras and Calcutta and cut the supply line to Burma by sinking as many Allied merchant ships as could be found. Central Force with the light carrier , the heavy cruiser , the light cruiser Yura and the destroyers and . would move westwards ready to support the northern or southern force as necessary around Point E, where many ships were anticipated.
The Southern Force, with the cruisers , and the destroyer Amagiri, was to be at Point F, 15°30′N, 83°20′E, to cut the southern part of the supply corridor. On the day after the attack on Ceylon the forces would rally at Point G, 16°30′N, 85°40′E, for the return journey to Mergui, passing south of the Andaman Islands, the 11 Destroyer Division rejoining. If the decided on a change plan, Malaya Force was to stay west of the Andaman Islands and continue its raid.
British preparations
Bay of Bengal In the Bay of Bengal, the British had only a couple of Royal Indian Navy sloops and the Greek destroyer for trade protection; merchant ships sailed in small unescorted groups, hugging the coast.
Ceylon Reinforcement of the Eastern Fleet depended on transfers from Britain and the Mediterranean. In late December 1941, a reassessment of the threat posed by Japan envisioned the Navy transferring the many of its big ships to the Eastern Fleet. Matters were made urgent by the Attack on Pearl Harbor that sank much of the United States Pacific Fleet and exposed British Malaya to attack. American reinforcement of the Atlantic and the pre-war rearmament was beginning to yield more big ships for transfer to the Far East but the Mediterranean Fleet sent far less reinforcements than expected, due to its losses in late 1941. Admiral James Somerville assumed command of an Eastern Fleet in March 1942 that was smaller than envisioned in December 1941.
Somerville divided the fleet into a fast Force A comprising the aircraft carriers and , the modernised battleship (flagship) the modern heavy cruisers and , the light cruisers and , with six destroyers. Force B was formed around the old carrier and four un-modernised s, , , and , the old light cruisers , and the Dutch , with eight Australian, British and Dutch destroyers, plus several submarines. The ships had not operated together and ship and air crews were deficient in training.
Signals intelligence The Far East Combined Bureau (FECB) intelligence assessment of the strength of the Japanese force was mistaken, identifying only two carriers in the Japanese force. FECB also believed the Japanese would sail from Staring Bay on 21 March and that C Day was 1 April. Somerville planned to evade the Japanese during the day and close for torpedo attacks at night with radar-equipped Fairey Albacore torpedo-bombers. Somerville had orders from the Admiralty, to protect the communications in the Indian Ocean and to keep the Eastern Fleet in being by avoiding risks but sailed to attack the Japanese force, having been convinced by the FECB that its assessment was accurate.
Prelude
Beginning on 25 March the (Imperial Japanese Navy Air Service) was made responsible for air reconnaissance over the Bay of Bengal. Daily sorties were flown by three to five flying boats from Port Blair in the Andaman Islands, out as far as east of the Indian coast. The sorties were intended to uncover British intentions, after they had sent Hudson bombers over the Andaman Islands, alarming the commander of the 22nd Air Flotilla in Bangkok.
On 29 March he transferred ten fighters from Tavoy (now Dawei) that flew daily patrols for four days, deterring the Hudson bombers from prowling over the islands.Reconnaissance reports showed that an offensive operation by the Eastern Fleet was not likely and that Operation U, the transfer of army divisions to Rangoon could continue. After concentrating the force at Mergui in Burma, Ozawa departed at 11:00 on 1 April and sailed south of the Tavoy Islands in the estuary of the river Dawei. At 13:00 the force turned south-west to pass between the Andaman Islands and the Nicobar Islands further south.
Raid 5 April On 5 April, at 16°N, 88°E, Malaya Force divided into North, Centre and South forces, to search for targets south of False Point (20°20′N, 86°44′E) and Cocanada (now Kakinada) (16°57′N, 82°15′E). Northern Force comprised the cruisers Kumano, Suzuya and the destroyer Shirakumo. Centre Force consisted of the aircraft carrier Ryūjō, the cruisers Chōkai and Yura with the destroyers Asagiri and Yūgiri. Southern Force was made up of the cruisers Mikuma, Mogami and the destroyer Amagiri.
6 April Northern Force
Northern Force had commenced its advance towards the coast at 06:00 on 5 April, then Kumano and Suzuya launched a Aichi E13A (Type 1) [Jake] seaplane each, to find targets. At 06:27 reported a merchant ship on a bearing of 320°, on a heading of 150°. The pilot, Lieutenant Itō Motoe then reported a tanker south of the freighter. At 06:38, the force commander, Vice-Admiral Takeo Kurita, ordered the Northern Force to sink both ships but soon afterwards, news arrived of six more ships on a bearing of 295°.
At 09:52 the Japanese ships opened fire on the northern-most ship at and soon set it on fire, then changed target to the six merchant ships that were on a bearing of 290°. The ships had left Sandheads, off Calcutta, at 18:00 on 5 April. Kumano and Shirakumo moved to the starboard flank and Suzuya manoeuvred to the south to cut off the ships. The freighters were sunk by 08:50, Kumano having fired of and of ammunition. Suzuya fired of and of Shirakumo fired from its guns. The bombardments were fired at with great accuracy because Itō observed the fall of shot.
At about 10:00, when Itō was returning from his sortie, he signalled that three Hurricane fighters had attacked him (actually, two Mohawk Mk IVs of 5 Squadron) on reconnaissance from RAF Cuttack along the coast. A New Zealand pilot, Flight-Lieutenant Keith McEwan, saw the Jake seaplane of Kumano preparing to take off about away and dived between Kumano and Shirakumo, fired about 600 rounds then got out of range of the cruisers. McEwan claimed the seaplane shot down but at 10:13 it landed to be hoisted aboard Kumano. At 12:16 the force completed its attack and turned to 180° to steam to Point G, the rendezvous at 16°30′N, 85°40′E. On 6 April, Kurita claimed eight freighters but had only sunk seven ships. At 06:00, crew on Elsa, a Norwegian tanker of 5,381 GRT, heading from Madras to Calcutta with of paraffin saw three ship silhouettes that turned out to be Japanese ships that opened fire. The crew abandoned the ship in life rafts as Elsa was hit and caught fire. One member of the crew of 30 was killed and several wounded.
A British merchant ship, of 9,066 GRT, en route to Colombo was sunk with the loss of 25 members of the 154 crew. , a British 7,621 GRT merchant ship, was sailing to Britain from Calcutta and Durban. The survivors reached land in Orissa Province on 8 April, with the loss of 16 members of the crew. a British 6,622 GRT was sailing to Mauritius when it was sunk with the loss of two men from its 83 crew. The US steamer SS Exmoor (4,986 GRT) was heading for Colombo with of goods until sunk at 09:15 with no casualties as was another British ship of 4,921 GRT, also with no casualties. On the British 2,441-GRT merchant ship three men were killed in the sinking.
Central Force
At 06:00 four Kates took off for Vizagapatnam anticipating many ships to be in the harbour. Two Kates carried four bombs and the other two with a bomb with the four bombs. The Kates flew north, parallel to the coast to avoid Flak and two seaplanes were catapulted off Chōkai to reconnoitre British shipping. After about thirty minutes a Westland Wapiti of the 6th Coast Defence Flight, Indian Air Force (Volunteer Reserve) spotted the Japanese ships and got off a sighting report of an aircraft carrier, a battleship, a light cruiser and two destroyers at 17°40′N, 83°50′E on a heading of 35°. The British commanders realised that a second raiding force was loose in the Indian Ocean, about off Vizagapatnam and with the Eastern Fleet busy south of Ceylon, they could only warn merchant vessels in the area of the danger.