Air raid on Ceylon (9 April 1942)

The Air raid on Ceylon (9 April 1942) was an air attack on Trincomalee, British Ceylon (now Sri Lanka) during the Indian Ocean raid (31 March – 10 April 1942) by naval aircraft of the 1st Carrier Fleet of the Imperial Japanese Navy. The Japanese objective was to destroy the Eastern Fleet in harbour.

The British had received warning of the raid through decrypted Japanese wireless messages in March 1942, from later air reconnaissance and by radar. The British forestalled the Japanese Navy by dispersing shipping from Trincomalee before the attack. The Japanese aircraft were met by fighters of 222 Group, Royal Air Force, the Fleet Air Arm and anti-aircraft guns.

Port facilities at Trincomalee were damaged, was set on fire and others were damaged. The bulk of the Eastern Fleet was at sea and escaped but several ships, including the aircraft carrier , were spotted and sunk. The Eastern Fleet moved temporarily to East Africa, from where it sent carrier forces into the central and eastern Indian Ocean. The Japanese Navy was unable to repeat the raid because of its commitments in the Pacific.

Background

British Ceylon (Sri Lanka)

Ceylon (now Sri Lanka) is off the south-east of India between shipping routes from Singapore and Rangoon to the Red Sea and the Persian Gulf. There are natural harbours at Colombo on the south-western coast and Trincomalee on the north-eastern coast, a naval anchorage and base. Ceylon was a geographically important part of the British Empire and its system of trade, communication and military organisation. In the 1930s more shipping tonnage was handled in Ceylon than all the ports of India. Since the beginning of the Second World War, the colonial government had engaged in mass recruitment for local defence, overseas labouring and expanded food production. Tea and rubber production was emphasised and rubber output rose from in 1941 to in 1943. The 3,600 workers in civil engineering converted to the repair and refitting of ships and the manufacture of dummy aircraft, guns and radar installations.

When the Pacific War began on 7 December 1941, the Allied disasters in the Pacific, Malaya and the British débâcle at the Battle of Singapore in February 1942 made Colombo Harbour the basis for eastern trade and the centre for the assembly of Indian Ocean convoys. Colombo port was large enough for 45 ships but soon had 100 to 110 ships at once, causing much overcrowding. The strategic importance of Ceylon increased and British planners deemed the island essential to the defence of India and Allied lines of communication through the Indian Ocean. The Allied defeat in the Dutch East Indies campaign (11 January – 9 March 1942) left the Indian Ocean vulnerable to Japanese attacks. The Malacca Strait in the Netherlands East Indies was about east of Trincomalee, making Ceylon a useful base for attacks on Japanese ships sailing to Rangoon in Burma.

From September to December 1941, 710 troop reinforcements arrived on the island, followed from January to March 1942, another 2,612; during April and June, 2,112 more troops joined the garrison (2,872) and 4,993 troops moved between the Far East and Ceylon from October 1941 to March 1942. The extent of the disasters that befell the British in early 1942, led in March to Admiral Sir Geoffrey Layton being installed as the Commander-in-Chief, Ceylon, with authority over the military forces on the island and over the civilian governor, Sir Andrew Caldecott, "Do not ask permission to do things. Do them and report afterwards what you have done". Layton found the same complacency and inertia in Ceylon as he had experienced in Malaya,

222 Group RAF

In September 1941 the Royal Air Force (RAF) established 222 Group (Air Vice-Marshal John D'Albiac) on the island in command of 273 Squadron at China Bay airfield with four Vickers Vildebeest and four Fairey Seal torpedo bombers. Until February 1942, the air defence of Ceylon had been a Royal Navy responsibility and 803 Naval Air Squadron (803 NAS) and 806 Naval Air Squadron (806 NAS) had transferred to Ceylon from the Middle East, six Fairey Fulmars at a time. Eight Hurricanes that had been assembled at Karachi, were flown to Ceylon, six of the Hurricanes, ferried to Ceylon by pilots of 136 Squadron, arrived at RAF Ratmalana on 23 February.

788 Naval Air Squadron (788 NAS) the Torpedo Bomber Reconnaissance Pool, with six Fairey Swordfish, for the Eastern Fleet (Vice-Admiral Sir James Somerville) was formed on 18 January at China Bay, near Trincomalee and was pressed into service in defence of Ceylon. By March 1942, airfields existed at China Bay, Ratmalana near Colombo, an airstrip was built at the Colombo Racecourse to relieve congestion at Ratmalana and another had been built at Minneriya on the south coast. China Bay was a grass landing ground that had the sea at both ends and there was a ridge along the southern edge; a low ridge ran along the northern boundary. Aircraft could only land and take off to the north-east or south-west, depending on the wind direction. There were fuel storage tanks beyond the north-east corner of the airfield at the Royal Naval Base Trincomalee.

Anti-aircraft defence comprised four obsolescent QF 3-inch 20 cwt anti-aircraft guns at Trincomalee. The danger of an attack by aircraft of the Japanese Navy aircraft-carriers was acute after the Attack on Pearl Harbor in December 1941 and the Bombing of Darwin in February 1942. The airfields at Ratmalana, near Colombo and China Bay were expanded to make room for more aircraft. Throughout the period, the Japanese were unaware of the bases at the Colombo Racecourse and Koggala.

Aircraft reinforcements

On 6 and 7 March the aircraft carrier dispatched sixty Hurricanes of 30 Squadron and 261 Squadron, originally intended for Java. On 30 March, the RAF reconstituted 258 Squadron that had been mauled in the fighting in British Malaya, Sumatra and Java. By 4 April, 803 NAS and 806 NAS of the Fleet Air Arm were ready with 24 Fulmars; the ground defences had been reinforced to 144 anti-aircraft guns. On 5 April, there were 37–38 serviceable Hurricanes near Colombo.

The first Consolidated PBY Catalina long-range flying boat of 413 Squadron Royal Canadian Air Force (RCAF) arrived on 28 March, with the ground crews following on by sea, two more arrived before the raid and on 6 and 7 April two more Canadian Catalinas arrived. By 4 April, four 205 Squadron RAF Catalinas had reached the island. There was one operational Dutch Catalina of the Netherlands Naval Aviation Service (MLD); two of the RAF and three Dutch Catalinas were unserviceable. The Catalinas were based at Koggala lagoon, at the south end of the island.

British code-breaking On 4 December 1941 the Japanese had altered their code JN-25B that prevented British code-breakers of the Far East Combined Bureau (FECB) from reading Japanese wireless messages. On 3 March 1942, the British broke JN-25B messages again. By the middle of the month, decrypts revealed that the 1st Carrier Squadron and the 2nd Carrier Squadron were at Staring Bay in the Celebes, an Imperial Japanese Navy fuelling base and that the 5th Carrier Squadron was en route. Around 20 March, decrypts revealed that a carrier force in Area D was going to attack DG on 2 April (C Day). On 28 March the FECB inferred that DG was Colombo. Japanese preparations were delayed by the late arrival of the 5th Carrier Squadron at Staring Bay on 24 March and the fleet sailed 26 March.

The British air defences in Ceylon were alerted to be ready for an attack on 1 or 2 March and merchant shipping was dispersed from Colombo. The Eastern Fleet sortied on 30 March to patrol south of the island. Aerial reconnaissance by Catalina flying boats concentrated on the south-east, the right direction that the Japanese would approach but with no sightings. The Eastern Fleet retired late on 2 April toward Addu Atoll to refuel at Gan (Port T) about south-west of Ceylon. and two s, sailed for Colombo, Cornwall to resume its refit and Dorsetshire to escort a troop convoy. set out for Trincomalee.

Radar Radar stations, code-named Air Ministry Experimental Stations (AMES) were established at Colombo (AMES 254) whose personnel arrived on 18 March and its equipment four days later. The station became operational at the Royal Colombo Golf Club (about north of Ratmalana) on 25 March and was connected by telephone to No. 20 Operations Room on 28 March; AMES 272 was set up at Trincomalee. The terrain around the radar limited maximum range to and the altitude of an object affected detection range. The short time that AMES 254 had been in Colombo may not have been sufficient to train operators to identify false radar echoes produced by local conditions; real echoes may have been mistaken for false ones. The radar antenna projected "lobes" in which objects might be detected, with gaps between lobes or lobes overlapping. The trajectory of the incoming Japanese aircraft may have flown in gaps between lobes. The distance travelled by Japanese aircraft between the maximum range of AMES 254 to Ratmalana was It took about 17 minutes flying time for a Japanese Zero and five minutes for Hurricanes to take off and six to climb to interception altitude. There were only six minutes for AMES 254 to report to 20 Operations Room and for orders to be issued to pilots if they were going to avoid being caught climbing.

Japanese preparations

The Japanese began planning for operations in the Indian Ocean on 14 February 1942. By 21 February, the Southern Army Commander, General Terauchi Hisaichi, and Vice Admiral Ozawa had come to terms. Once the Strait of Malacca had been cleared of mines (late February – early March) Operation T, a landing in northern Sumatra would begin. About twenty days after the end of the minesweeping operation, Operation D, the invasion of the Andaman Islands.

Operation U was the transport of two Japanese army divisions from Singapore and Penang to Rangoon in Burma. Land-based naval air units would transfer to Bangkok for air support. It was thought necessary to forestall British naval reinforcements to the Indian Ocean and the Japanese Admiralty and the Combined Fleet devised a scheme for a raid into the Indian Ocean against the Eastern Fleet in Ceylon. The Striking Force was in the area operating against the Dutch East Indies.

On 9 March 1942 the Southern Force (Admiral Chūichi Nagumo) received orders to protect Japanese sea communications from attack by the British army in Burma and to "sweep the Bay of Bengal clear of British naval units", ready for the occupation of the Andaman Islands and the Nicobar Islands in the eastern Indian Ocean. In February 1942, the Japanese army and navy conducted a war game to examine an invasion of Ceylon but both services were lukewarm. The army did not have the troops for an invasion and occupation; the navy was preoccupied with its operations in the Pacific.

There were insufficient ships to shift an invasion force and to supply a garrison against attacks by British ships, submarines and aircraft. The Prime Minister, Hideki Tojo, rejected the plan indefinitely. By 16 March, the plan for an Indian Ocean raid was to depart from Staring Bay in the Celebes (now Sulawesi) in the Netherlands East Indies on 26 March, ready to attack Colombo on 5 April (C day). The Southern Force was based on the five aircraft carriers of the 1st Air Fleet, comprising of the 1st Carrier Squadron, and of the 2nd Carrier Squadron, with and of the 5th Carrier Squadron.

Prelude

2−6 April