This was a British deception scheme to shield the left flank of Lieutenant General Sir William Slim’s 14th Army as it advanced to the south along the Irrawaddy and Sittang rivers toward Rangoon and southern Burma (April 1945).
‘Conclave’ sought to persuade General Heitaro Kimura’s Burma Area Army that the British and Indian forces had been concentrated in the area of Yinmabin and Hopong to the west and to the south-east of Mandalay respectively.
Under the auspices of Lieutenant General Sir Oliver Leese’s Allied Land Force South-East Asia command, ‘Conclave’ was one of two undertakings designed to facilitate the advance of the 14th Arm. The more southerly of these depended largely on the Royal Air Force which, with the help of the Royal Navy, was to simulate an assault on Bassein in the south-west of the main body of Burma; and the more northerly was ‘Conclave’. This latter involved a large number of groupings (the Special Operations Executive’s Force 136 and its guerrilla groups, the American Office of Strategic Services and the ‘D’ Division strategic and tactical deception organisation, all of which were represented at the headquarters of the 14th Army.
Linked with ‘Tarzan’, ‘Conclave’ was designed to threaten the escape route of Lieutenant General Shihachi Katamura’s 15th Army through the Shan States, thereby deflecting Japanese attention to the east of main British and Indian thrust to the south along the Sittang river from Meiktila, while ‘Cloak’ directed their attention to the west. ‘Conclave’ was allocated to a supposed extemporised grouping comprising Major General D. D. Gracey’s real Indian 20th Division and the fake Indian 51st Tank Brigade. The operation was also to create the impression that paratroops were being dropped along the road linking Thazi, Taunggyi and Loilem to isolate and destroy all the Japanese forces to the north of it.
Although for a time it seemed that this operation was achieving a measure of success, and it was even reported that Japanese were retreating farther to the east in the direction of the Salween river, it was in fact ineffective. The Japanese either ignored it or were unaware of it.