'Twist' was a British naval undertaking to demolish a jetty at Myebon on the estuary of the Kaladan river in the Arakan western coastal region of Japanese-occupied Burma (26 February 1943).

Toward the end of 1940 coastal craft similar to those operational in the English Channel and Mediterranean were shipped to the East Indies Station and work began on the construction of others India. On 16 June 1942 Captain J. Ryland was appointed Captain Coastal Forces East Indies Station, and by this time harbour defence motor launchers had been delivered to Indian ports and Indian-built Fairmile motor launches were being launched in Calcutta and Bombay. The first officers to serve in Coastal Forces were mostly volunteers from the Royal Indian Navy and its reserves, and also a few from the Royal Navy Volunteer Reserve who had served in British coastal craft in other theatres, and the base at Trombay was commissioned on 1 October 1942.

Lieutenant Commander J. H. Heather’s 55^th Flotilla was the first Indian flotilla to be commissioned and, on 19 December its five motor launches departed to Chittagong for operations against the Japanese. Shortly after the departure of the 55^th Flotilla, Lieutenant Commander H. M. Darbyshire’s 120^th HDML Flotilla was commissioned.

Given the fact that the Japanese were on the offensive in Arakan at this time, there was little time available for the flotillas to work up according to standard procedures and all effort was bent to support of the British and Indian forces in Arakan. Thus the 55^th Flotilla formed the core of Commander Humphrey’s Force 'Z'. This force departed on its first night exercises on 18 January 1943 and, a few days later, ML-439 carried out a survey of the Naf river. This survey resulted in the force being moved to an advance base 1 mile (1.6 km) to the north of Teknaf. Force 'Z' was then divided into two patrols with the task of gathering information about the Japanese and interrupting their seaborne communications.

The first patrol, which comprised ML-477, ML-441 and ML-440, departed on 24 January and, after entering the Mayu river, engaged two Japanese troop-carrying launches. One of the launches was found to be armed and was sunk, and the other was forced ashore. The second patrol entered Akyab harbour without opposition and, as there were no troops available to investigate whether or not the Japanese were using Oyster island as an Observation Post, an officer and an other rank of the patrol landed to do this and returned with the information that there was no evidence of any Japanese presence.

An operation was then undertaken, in combination with Lieutenant Colonel H. M. Boxer’s 6^th (West Africa) Brigade that was to make landings on each side of Foul Point, thus surrounding the Japanese. ML-438 and ML-441 provided cover as armour was landed, but this was soon surrounded and put out of action. One further attack was made by moonlight, but this was also unsuccessful, so the planned 'Oscar Wilde' was cancelled on 3 February 1943.

By now it was clear that a better knowledge of the Japanese defences was necessary before operations could be undertaken, so Lieutenant P. Munro departed in ML-440 to take short-range photographs of the Japanese defences along the coast at Akyab, and these provided valuable information about the beach defences. Some of Force 'Z' then carried out escort duties between the Naf river and Chittagong. Others remained in Chittagong for the rectification of engine problems. Experience had shown that the Japanese did not wish to fight the launches of Force 'Z' at sea, so night patrols were started in Combermere Bay, which was thought to be on the route of Japanese supply vessels running from Rangoon to Akyab via inland waterways. Sweeps into Kyaukpyu were carried out on two successive nights without making contact with the Japanese even though ML-439 entered the inner harbour. ML-438 and ML-476 continued patrolling the Mayu river and were fairly frequently engaged by shore batteries. Other elements of Force 'Z' carried out escort duties.

On 26 February the launches embarked a platoon of the Durham Light Infantry and a party of Royal Engineers for 'Twist'. This had been schemed for the demolition of a jetty at Myebon. On the following night the flotilla, led by ML-439, sailed up the approach creek, which was known to be held in strength by the Japanese on both sides. At 23.00 the launches sighted the jetty on the port bow and, as Japanese machine guns opened fire from Myebon, the launches bombarded the town. The vessels then made fast alongside the jetty and the troops disembarked. While they had been approaching the jetty, ML-441 had proceeded up the river and blown up a ship of about 210 tons. Fuses on the jetty were lit at 04.30 and the landing party had been re-embarked before the jetty blew up at 04.45. The force then returned with Japanese prisoners of war for interrogation.

As it was thought that Japanese submarines were operating in the Bay of Bengal, Force 'Z' carried out anti-submarine patrols for a short while returning to Teknaf on 9 March after ML-439 had carried out a gunfire bombardment of Donbaik in the face of heavy Japanese fire. The launches were then pulled back to refit in Vizagapatam, and on their return ML-474 and ML-438 each towed a landing craft to Chittagong and thence on a secret mission which entailed landing agents behind the Japanese lines and picking them up again two days later. This undertaking was carried out successfully, and many similar operations were then planned for and carried out by these two motor launches. These operations often entailed long passages in Japanese-controlled waters: well beyond the normal cruising range of the motor launches, such undertakings necessitated the stowage of high-octane fuel on deck, a fact which added greatly to the danger when attacked by Japanese aircraft.

Commander R. R. W. Ashby was appointed to command the Arakan Coastal Forces at this time, and the 55^th Flotilla was joined by the 56^th Flotilla of the Royal Indian Navy, the African-manned 49^th Flotilla and three motor launches of the Burma navy. Various operations to interrupt Japanese sea and inland water links were undertaken by ML-439, ML-475 and ML-476. These took the form of sweeps round Foul island, Danson Bay, Bonnie Bay and Bluff Cape. The force returned to Chittagong on 24 December after carrying out a sweep of Combermere Bay. ML-440 and ML-438 remained in the bay after the other motor launches had sailed, but rejoined two days afterwards.

One week later ML-439, ML-441 and ML-476 bombarded Ramree island, meeting no opposition until the operation had been completed and course set for Chittagong. Six Japanese bombers then attacked with small bombs, which caused no damage. Not long after this 32 bombers and Mitsubishi A6M Reisen 'Zero' fighters attacked from a much lower level and achieved several near misses. The RAF had anticipated this action and counterattacked, claiming 13 Japanese aircraft shot down and another 10 probably destroyed. Information was soon received that the Japanese now feared a major attack and their cruisers in Singapore had orders to raise steam.

To continue worrying the Japanese, ML-475, ML-438 and ML-440 sailed to an anchorage off Cox’s Bazar on 8 January 1944, and flares off Unguan island seemed to indicate that the force had been observed. The approach to Ramree is less than 1 mile (1.6 km) wide, but the anticipated opposition was not forthcoming. All went well and, shortly before midnight, a fishing vessel was intercepted for interrogation and much useful information about Japanese dispositions was obtained. ML-440 had been detached earlier to investigate some small craft that had been sighted, and now returned to report that these were fishing vessels and had returned to harbour.