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Unless otherwise indicated, all material researched, written, and copyrighted by Bill Stone for publication in various venues online and elsewhere. Feel free to point links at these pages, but reproduction of this material, electronic or otherwise, is prohibited without prior permission in writing from Stone & Stone.

Vichy Indo-China vs Siam, 1940-41

Siamese Armed Forces

The Siamese army comprised 44 battalions (each known as a "khong phan") of infantry, 13 groups of artillery, 9 squadrons of cavalry, six battalions of engineers, three companies of tanks, one AA regiment equipped with 40mm weapons and a group of three AA companies armed with Bofors 75's. The armored force included 20 medium Armstrong 6-tonners, 35 light Fords armed only with machineguns, four "heavy" Landswerk tanks of eight tons with 100mm gun, and 12 Vickers armored cars. Other Siamese equipment, supplied by a variety of nations, was similarly aged. When mobilized the army amounted to some 50,000 troops organized into six military regions containing five infantry divisions.

The air force, with about 500 pilots, flew 100-150 combat aircraft including 36 Vought Corsairs, 48 Curtiss Hawks, and 6 Glenn Martins. (Between 1939 and 1941 Siam was also in the process of re-equipping with Japanese aircraft.) The navy, which was particulary pro-Japanese, contained two coastal defense ships, ten Italian-built torpedo boats, and two submarines.

Indo-Chinese Armed Forces

Vichy fielded some 41 infantry battalions in all of Indo-China at the end of 1940, supported by two regiments of artillery, a battalion of engineers, a few tanks, and some AA guns. These figures are somewhat misleading, though, due to reductions caused by casualties and desertions in September. About half the infantry (including one of my favorite units, the Bataillon de Tirailleurs Montagnards du Sud-Annam) plus most of the artillery and tanks eventually concentrated along the border.

The warships on hand amounted to the light cruiser Lamotte-Picquet, two 2000-ton sloops, and two 600-ton sloops. (The only submarine in Indo-China was lost on maneuvers on 15 June 1940; two others did not arrive until 6 March 1941.)

Vichy air forces totaled around 100 aircraft: 17 Morane-406 fighters (seized by Hanoi while en route to China; unfortunately, most of the armaments for these planes had already reached Chiang Kai-Shek), 4 Farman-221 and 6 Potez-542 bombers, 10 Loire-130 seaplanes, and 60 Potez-25 TOE scoutplanes. This was a feeble force, especially given the reduced firepower of the Moranes.

Metropolitan Vichy wished to dispatch four battalions of Senegalese infantry from Djibouti to Saigon, and Hanoi also sent a purchasing commission to the United States in an attempt to secure aircraft, weapons, and war materiel; neither initiative succeeded.


Siamese provocations along the border with Laos and Cambodia began in September 1940 and its army was gradually assembled in eight sectors with a total of 29 battalions. The strongest grouping took shape with tanks and artillery on the route from Bangkok to Battambang.

At the end of October local Vichy troops moved into covering positions along the frontier. Reinforcements were also dispatched by General Martin in Hanoi, with the general pattern of deployment calling for three main sectors with a center of gravity in the south along the axis Battambang-Bangkok. This deployment was severely limited by the need for battalions to re-assert Vichy control in northern Tonkin where bandits and nationalist partisans were active in the wake of the defeat at Lang Son, by the disruption to the Vichy army caused by losses, desertions, and plummeting morale during the recent fighting against the Japanese, and by the dismal state of the transportation network serving the remote border areas. The bulk of the Vichy air strength, such as it was, also moved to airstrips near the border.

During the daylight hours Siamese aircraft controlled the skies, bombing Vichy positions and raiding Battambang and Vientiane. At night Vichy planes retaliated against Siamese troop concentrations and towns. Vichy pilots claimed at least four air-to-air victories; Siamese bombers damaged the Vichy patrol boat Beryl.

While both sides built up forces and accumulated supplies, ground fighting began to escalate. Patrols and raiding parties were dispatched across the border by both sides; both sides were caught in ambushes; border positions were probed by increasingly large bodies of troops; artillery fire was exchanged; and casualties -- both civilian and military -- began to mount.

Still there was no general offensive or declaration of war.

Ground Campaign

At the beginning of January 1941 Siam, unable to regain its "lost provinces" through diplomatic pressure and bluff, finally mounted an offensive.

In northern Laos three battalions crossed the border on the 10th against negligible opposition and occupied the entire western bank of the Mekong north and south of Paklay. Meanwhile, three Siamese battalions facing Vientiane across the Mekong made no move.

In southern Laos on 12 January the Siamese attack began in the direction of Pakse; on the 15th, supported by artillery fire and aerial bombing, three battalions of infantry dislodged the Vichy defenders who retired across the Mekong and by the 19th ceded control of the western side of the river as far south as the Cambodian border.

On the northern border of Cambodia in the Dangrek Range another group of three battalions faced scattered Indo-Chinese border posts. The attackers did not emerge until 20 January to press south where they burned and destroyed Samrong before being halted by reserves of the 2nd battalion of the Regiment de Tirailleurs Annamites - bis.

The strongest Siamese force -- nine battalions and two groups of artillery supported by tanks -- attacked on 10 January in the Poipet sector on the road to Battambang. The Vichy covering force proved unable to halt the advance which continued in the direction of Sisophon. Here, however, the Vichy masse de maneuver waited.

On the night of 15/16 January the Vichy spearhead (four battalions, each from a different regiment) and supporting tanks and guns moved into position to mount their counter-offensive; it was launched from northwest of Sisophon against the left flank of the Siamese advance on the morning of the 16th. The Siamese were alert, the attack was uncoordinated and poorly executed, and the battle did not go as the Vichy commanders had planned. Siamese aircraft controlled the skies and their tanks were well-handled in counterattacks which were only stopped by Vichy 75mm AA guns. By the end of the afternoon the Vichy attackers had withdrawn.

While the attack did not gain its objectives, Vichy claimed to have inflicted some 800 Siamese casaulties against only 120 of its own. Those claims seem exaggerated, but the Siamese advance came to a halt.

Naval Battle

On the same day Vichy launched its counterattack from Sisophon, Vichy's Indo-Chinese flotilla sought the Siamese fleet. Two seaplanes spotted Siamese vessels near Koh Chang island off the coast of southeast Siam near the Indo-Chinese border on the afternoon of the 16th, and the Vichy warships prepared to attack in the morning.

Under the tricolor steamed CL Lamotte-Picquet and gunboats Dumont d'Urville, Admiral Charner, Marne, and Tahure. The Siamese squadron consisted of coastal defense ships Sri Ayuthia and Dhonburi with torpedo boats Songkhla, Cholbury, and Trat. Fire commenced at 0614 on 17 January and continued for two hours as the vessels maneuvered through mists in the restricted waters of a maze of islands and unmapped shoals.

When it was over, Dhonburi, Cholbury, and Songkhla had been sunk and the remainder of the Siamese force was heavily damaged and out of action. The Siamese air force sent two planes against the withdrawing French warships, but, like the Siamese navy, they scored no hits.


At this point Japan announced that it would be "mediating" the conflict; in preparation for the upcoming ceasefire, both sides attempted to improve their positions on the ground. Siamese troops began working their way around Sisophon to the north, but were halted by 2nd battalion of the 9th Regiment d'Infanterie Coloniale. Following this action and some minor French ripostes elsewhere on the front, fighting died down.

On 28 January the Japanese-sponsored ceasefire became effective. Three days later the preliminary documents were signed aboard CL Natori at Saigon. On 7 February negotiations for the final settlement commenced in Tokyo and, finally, on 9 May, the peace accords were signed.


Aldrich, Richard J. THE KEY TO THE SOUTH: BRITAIN, THE UNITED STATES, AND THAILAND DURING THE APPROACH OF THE PACIFIC WAR, 1929-1942. Kuala Lumpur: Oxford University Press, 1993.

Auphan, Paul and Jacques Mordal. THE FRENCH NAVY IN WORLD WAR II. Annapolis: Naval Institute Press, 1959.

Christienne, Charles and Pierre Lissarrague. A HISTORY OF FRENCH MILITARY AVIATION. Washington, DC: Smithsonian Institution Press, 1986.

Hammer, Ellen J. THE STRUGGLE FOR INDOCHINA, 1940-1955. Stanford: Stanford University Press, 1966.

Hesse d'Alzon, Claude. LA PRESENCE MILITAIRE FRANCAISE EN INDOCHINE (1940-1945). Chateau de Vincennes: Publications du Service Historique de l'Armee de Terre, 1985.

Rohwer, J. and G. Hummelchen. CHRONOLOGY OF THE WAR AT SEA, 1939-1945. Annapolis: Naval Institute Press, 1992.

Copyright © 1998 by Bill Stone
May not be reproduced in any form without written permission of Stone & Stone



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