This was an Allied (largely British) plan for the occupation of Thailand in the light of Japan’s imminent collapse (August/September 1945).
Basic plans for the occupation of Thailand in ‘Bibber’ and French Indo-China in ‘Masterdom’ had already been developed by the Joint Planning Staff of Admiral the Lord Louis Mountbatten’s South-East Asia Command, and were promulgated on 31 August for parallel undertakings to be performed in six phases: two Recovery of Allied Prisoners of War and Internees (RAPWI) hospitals were to be flown into Bangkok on 3 and 4 September; one infantry brigade group of Major General G. C. Evans’s Indian 7th Division, the 207th Military Mission and an RAF element (parts of Nos 20 and 211 Squadrons) were to be flown into Bangkok from the date that Major General E. C. R. Mansergh’s Indian 5th Division landed in Singapore; one infantry brigade group of Major General D. D. Gracey’s Indian 20th Division, an Allied Control Commission and an RAF element (parts of Nos 28 and 684 Squadrons) were to be flown to Saigon via Bangkok; the rest of the Indian 7th Division was to be flown into Bangkok, with its vehicles moved by sea; the rest of the Indian 20th Division was to be moved to Saigon by sea’ and Major General H. M. Chambers’s Indian 26th Division was to be moved to Bangkok by sea if and when required. In all, the parallel operations involved the movement of 26,684 men and 2,340 vehicles to Bangkok, and of 25,748 men and 2,400 vehicles to Saigon.
The delivery and maintenance of the forces in Thailand and French Indo-China were to be an RAF responsibility until a maritime link with Bangkok and Saigon could be established, and for the task five RAF squadrons, each of 20 Douglas Dakota transport aircraft, were grouped at Mingaladon and Hmawbi airfields in the area of Rangoon. At the other end of the Burma-based air service were Don Muang airfield outside Bangkok and Ton San Nhut airfield outside Saigon, which could handle as many as 100 sorties per day, though the calculation of deliveries had to take into account that in the time up to mid-November, adverse weather would make it possible to fly on only two out of every three days.
The tasks of the Allied forces in Thailand and French Indo-China had similarities inasmuch as in Thailand they were to deal with Japanese troops and rescue prisoners and internees, and in French Indo-China to disarm all Japanese troops to the south of 16° N and rescue prisoners and internees as Gracey exercised control over the headquarters of Field Marshal Count Hisaichi Terauchi’s Southern Expeditionary Army Group in Saigon, issue orders to Terauchi and see them carried out. There the similarity ended, for as the Thais had by now agreed to place their armed forces at Mountbatten’s disposal, there was to be no military occupation of Thailand as the SEAC forces in that country were there merely to help a friendly country rid itself of surrendered invaders and repatriate prisoners held by them. In French Indo-China, on the other hand, the SEAC forces, in addition to dealing with the Japanese and rescuing prisoners and internees, were there to keep order pending the re-arrival of the French. But the country had declared itself independent and was therefore hostile: there was no question of Allied troops being used to retake the country for the French, and Gracey was under orders not to occupy more of it than was necessary for his task, for the reoccupation of the whole of the country was to be carried out in a second phase of operations by French forces with their own civil affairs representatives. In these circumstances, however, it was almost inevitable that Gracey’s task would involve some combat, and in spite of every effort to avoid them clashes with the Viet Minh forces did take place.
Early in the morning of 3 September the Indian 7th Division’s advance party was delivered by air from Hmawbi airfield to Don Muang, where it was received by high-ranking Thai officials and a guard of honour. With the ready co-operation of the Thai authorities RAPWI immediately began work, while the headquarters of the Indian 7th Division established the staging post for the Indian 20th Division and Allied Control Commission that were to move to Saigon, and began planning for the arrival of the rest of the Indian 7th Division. Two days later Lady Mountbatten and Major General T. O. Thompson, SEAC’s director of medical services, arrived in Bangkok and set out to see conditions in the prisoner of war and internee camps.
Pending the availability of suitable accommodation in Bangkok, Evans established his headquarters at Don Muang airfield, and on the afternoon of 3 September summoned representatives of Lieutenant General Aketo Nakamura’s 18th Area Army, responsible for the Japanese garrison of Thailand from 4 January 1943, initially as the Thailand Garrison Command, and then as the 39th Army from 14 December 1944 to 7 July 1945. As there was no accredited representative of Terauchi available, Evans took note of the forces controlled by the 18th Area Army and ordered that Terauchi’s accredited representative be attached immediately to his headquarters as the transmission channel for SEAC’s orders to the Japanese forces in Thailand. Daily conferences were held at which Japanese representatives were given orders and produced information about the strength and distribution of their forces. On 5 September the 18th Area Army was instructed that all Japanese troops, except those employed in the maintenance of essential services, were to be confined to their billets and that a report was to be prepared at once showing the numbers, types and location of all wireless sets down to regimental level and of telephone switchboards down to divisional level.
On 6 September Brigadier H. W. Dinwiddie’s Indian 114th Brigade, under the temporary command of Colonel Kalwant Singh, started to arrive by air, and as the brigade was brought up to full strength over the following three days, it assumed responsibility for the protection of Don Muang airfield, and also for guard and other duties in Bangkok. At the same time Brigadier A. T. Wilson-Brand, heading the military mission, assisted by a Thai major general, a representative of the 18th Area Army and a staff officer of the Indian 7th Division, prepared a plan for the concentration of Japanese troops and the siting of dumps for surrendered arms and ammunition. On 8 September Evans ordered this scheme to be put into effect.
Thailand was divided into 11 concentration areas, each of them centred on a town containing a Japanese headquarters of some sort which was to be responsible for disarming all troops in its area, collecting them in camps and mounting guard over dumps of surrendered military matériel pending the arrival of Thai or Allied troops. Disarmament was to begin at once, and some 16,000 disarmed troops from Bangkok were to move immediately to the nearest concentration centres, leaving only detachments required by the local Allied commander for essential working parties. Thai troops were to take over the barracks and billets evacuated.
It had been intended that Brigadier J. S. Vickers’s Indian 33rd Brigade of the Indian 7th Division should be brought in by air in about the middle of September, but bad weather and heavy calls for urgent movement of supplies delayed the arrival of this brigade, and also of Brigadier I. C. A. Lauder’s Indian 89th Brigade, until a time well into October. Nevertheless the disarming and concentration of Japanese forces progressed steadily, and by 1 October about 84,000 Japanese had been disarmed and some 49,000 of them moved into the concentration areas despite an acute shortage of transport: none of the Indian 7th Division’s vehicles had arrived, so only Japanese transport, all of it in very poor condition, was available. The military mission ensured that the Japanese handed over their arms and ammunition dumps to Thai troops, to whom Force 136 of the Special Operations Executive, which had already been operating in the country, also handed over all that it collected in outlying areas.
On 19 September the 18th Area Army provided a detailed order of battle of the Japanese forces in Thailand. The major formations and units in the country were the 4th Division, Lieutenant General Kiyoe Yamamoto’s 15th Division, Lieutenant General Masachika Hirata’s 22nd Division, Lieutenant General Nobuo Tanaka’s 33rd Division, Lieutenant General Yuichiro Nagano’s 37th Division, Lieutenant General Yuzo Matsuyama’s 56th Division, Major General Kanehiro Ohara’s 72nd Independent Mixed Brigade and 1st Air Service Corps. The 4th Division and 22nd Division each possessed only two regiments, and the 33rd Division had only 6,000 men including all its subordinate units. No figures were available for the 15th Division which was probably, in view of its previous history in Burma, still weaker. The 72nd Independent Mixed Brigade had nearly 6,000 men and the 1st Air Service Corps more than 7,000. The total strength of the 18th Area Army, excluding the 15th Division and some minor units, was given as 105,098 men.
Apart from these ‘surrendered personnel’ there were about 1,100 prisoners of war, mainly officers and men suspected of war crimes, members of the Kempeitai military secret police and Hikari Kikan liaison force with client forces, and staffs of prisoner of war camps.
To take charge of these and of the Indian National Army and Japanese labour, a special organisation was established under Singh.
An operation instruction of the 28 September from the Allied Land Forces Thailand summarised the tasks to be tackled in Thailand, which were to ensure the security of Don Muang airfield; disarm, concentrate and hold all Japanese forces; supervise all surrendered arms and warlike stores; evacuate all Allied prisoners of war and internees; and co-operate with the Thai government in the preservation of law and order. To implement this, on arrival between 10 and 23 October, the Indian 33rd Brigade was to take over the western area comprising Nakhon Pathom, Ban Pong, and thence westward along the railway from Bangkok to Moulmein; on arrival between 6 and 10 October, the Indian 89th Brigade was to take over Bangkok and relieve the Indian 114th Brigade, which was then to take over the area to the north and east of Bangkok, comprising Nakhon Nayok, Sara Buri and Lop Buri; and Brigadier J. R. Lupton’s 7th Divisional Artillery was to take over the northern area consisting of Ubon, Nakon Sawang, Lampang and Chiengmai.
These widely separated concentration areas were initially needed to supervise the concentration of the many Japanese detachments scattered all over Thailand. By mid-November the preliminary concentrations had been completed and further concentration had begun of all surrendered Japanese into four areas near Bangkok, ready for repatriation when shipping became available. During this phase, which lasted into December, the only disturbances were an isolated raid by armed dacoits on a brigade workshop section at Ban Pong and some looting on the Burma/Thailand railway. To deal with the security of the railway some 2,700 Japanese were rearmed and patrolled it under their own officers, the Japanese being used since it had already been decided to reduce the Allied presence in Thailand and hand over responsibility for Japanese forces awaiting repatriation to the Thais.
On 10 December the Indian 7th Division began to move to Malaya, and on 26 January 1946 Headquarters Allied Land Forces Thailand was replaced by Headquarters British Troops Thailand and No. 455 Sub-Area was abolished. By the end of the month only the Indian 114th Brigade of the Indian7th Division, with a proportion of divisional troops, remained in Thailand. On 19 January a British inter-service parade and victory march was held in Bangkok, at which the king of Thailand took the salute.
From January to April the concentration of surrendered Japanese troops in southern Thailand and the repatriation of prisoners-of-war, internees and displaced persons continued, and European and Indonesian Dutch found fit for military service were trained and organised for operations in the Netherlands East Indies. In April the Indian 114th Brigade moved to Malaya and, apart from supply, transport, medical and welfare units, the only Allied troops left in Thailand were 1st Queen’s Royal Regiment, 13th Frontier Force Rifles Machine Gun Battalion, and a detachment of Indian Engineers. Major General G. Brunskill’s newly created Headquarters British Troops Thailand kept a close watch on the activities in Thailand of the Indian Independence League, which was trying to form an Indian National Volunteer Force, and on the situation on the border with French Indo-China, where the Thais were resisting attempts by the French to reoccupy the areas ceded to Thailand under orders from the Japanese in 1941.
With the release by General Douglas MacArthur of ships for the return of Japanese surrendered personnel, repatriation (excluding suspected war criminals and persons wanted for interrogation) from Thailand started in May and by the end of the month more than 25,000 had been evacuated, leaving 85,647 who were despatched without incident during the next few months, and in September 1946 the last Allied troops left Thailand.