This was an Allied deception plan, in support of the US/Chinese 'Iceman' and British 'Sceptical' (i), suggesting that forces commanded by General Douglas MacArthur were to make an amphibious landing at the southern tip of Japanese-occupied French Indo-China (autumn 1945).
The operation was schemed as a means of providing direct support for the proposed British offensive to advance on and take Bangkok, the capital of Thailand.
In the middle of July 1945, Admiral the Lord Louis Mountbatten, head of the South-East Asia Command, visited MacArthur in Manila, the liberated capital of the Philippine islands group, to co-ordinate the British and USA offensives in a series of meeting between 12 and 14 July. One of the agreements which emerged was that for 'Conscious', whose objective was the containment of Japanese forces in that part of Thailand to the north of the Kra isthmus and in French Indo-China in order to facilitate 'Zipper', and also to draw Japanese forces away from the southern flank of 'Carbonado'. The 'story' promulgated in 'Conscious' was that Mountbatten and MacArthur had agreed that as soon as the monsoon was over, on or about 1 November, Mountbatten’s forces would take the offensive toward Bangkok and those of MacArthur would provide support by a landing in the area of Saigon in Indo-China with the object of securing air bases. Radio deception and special means would then support the further 'story' that, as a result of force limitations and the need for commitments in Indo-China, MacArthur’s participation in the notional operation against Sumatra under 'Sceptical' would be reduced to air support from airfields in the southern part of Borneo airfields which were then being established as Australian troops involved in the 'Oboe' operations were mopping up the Balikpapan area of southern Borneo: operations by heavy bombers from Balikpapan were expected to begin in mid-August.
'Conscious' was forwarded to the Joint Chiefs-of-Staff Committee, from which approval was gained, but proceeded no further as the war ended in the middle of August.