This was a programme of British cruiser and Indian sloop patrols between the Andaman and Nicobar island groups and the west coast of Burma with the object of preventing the Japanese from evacuating their garrisons (May.15 June 1945).
These garrisons comprised Major General Yoshisuke Inoue’s 35th Independent Mixed Brigade in the Andaman islands group and Major General Toshio Itsuki’s 36th Independent Mixed Brigade in the Nicobar islands group.
The British believed that the Japanese might undertake such an effort to prevent the isolation of these two brigades in the islands of the Gulf of Bengal and also to reinforce the formations of General Heitaro Kimura’s Burma Area Army in mainland Burma.
Since 12 May the British light anti-aircraft cruiser Phoebe, subsequently reinforced by the Indian sloops Cauvery and Sutlej from Rangoon after its recapture, was the basis of Force 69 whose task it was to attack any Japanese shipping between the Tenasserim coast and the Andaman and Nicobar island groups, and on the Tenasserim coast between 10° and 15° N.
One boat, containing four Indian or Burman fishermen escaping from Port Blair, was intercepted on 20 May, and the refugees reported that the food situation in Port Blair was desperate.
The Tenasserim coast, between the limits above, was patrolled in daylight without sign of any Japanese activity at sea or in the air.
While Force 69 operated in the North Andaman Sea, the RAF’s No. 222 Group was operating against Japanese shipping in the South Andaman Sea. Consolidated Liberator heavy bombers of this group destroyed two small merchant ships, one of them in a depth-charge attack, between Sabang and the Nicobar islands group, on 22 May.
On 1 June the light cruiser Ceylon replaced Phoebe as the core of Force 69, and 'Adoption' was maintained by Ceylon and two or three Indian sloops on the east coast of the Andaman islands group and on the Tenasserim coast until 12 June, when Ceylon left the patrol area and headed toward Rangoon.
'Adoption' was formally terminated on 15 June, but the patrol was then maintained on a more limited basis by a single sloop. The sloops involved were Cauvery, Godavari, Kistna and Narbada, though the British frigate Lossie also spent eight days on patrol.
Further evidence of the privations now being suffered in the Andaman islands group was obtained on 4 June, when Kistna intercepted a small boat containing three native convicts. These men stated that they had been allowed to fish off Port Blair by the Japanese as a result of the food shortage in the islands, but had been driven by the weather to the Tenasserim coast.
On 8 June, Kistna sighted about 15 large sampans drawn up on a beach on Pulo Myang in the Gregory islands group in the Forrest Strait, and destroyed most of them in a gunfire bombardment.
No Japanese activity was observed on these coasts throughout June.