Vichy versus Asia: The Franco-Siamese War of 1941
Dr. Andrew McGregor
Aberfoyle International Security
In 1940 the Vichy government of French Indo-China was isolated and threatened
by the imperialist Japanese, the neighbouring Thais and by native rebel
movements. The French had about 50,000 colonial and metropolitan troops
stationed in the colony. They outnumbered the small French civilian population
of 40,000 colonists in a territory of 25 million Indo-Chinese. The French
collapse in the spring of 1940 resulted in the German occupation of 60% of
France, but Marshall Pé´¡inÖ©chy government retained control of the
remainder, as well as Franceà£¯lonial empire. Indo-China was, however, cut
off from re-supply from Vichy France. A British blockade proved effective,
meaning that troops could not be rotated for the duration of the war, nor could
parts be obtained for military equipment. Fuel supplies could also not be
replenished so long as the petroleum-short Japanese Empire controlled the Asian
Vichy diplomats attempted to persuade Germany to allow them to ship arms and
equipment to Indo-China, appealing to the Germans on racial grounds, pointing
out the possibility of the è©´e raceì¯³ing ground in Asia. The Germans
would promise only to speak to the Japanese. At the same time Vichy was fending
off offers from the Chinese to occupy Indo-China to â¯´ecté´ from the
Japanese. Aware of Chinaà¯·n irredentist claims in the area, the French
doubted they would ever get their colony back if the Chinese were allowed in.
The Japanese deliver a shock
As France fell, the Japanese began to make demands of the Governor-General of
Indo-China, General Catroux. When the General acceded to demands that rail
traffic to China be stopped he was promptly replaced. Vichy named the loyal
commander of the FNEO (Forces Navales dè´²eme-Orient), Vice-Admiral
Jean Decoux, as Governor General. By September Decoux was facing far greater
demands from the Japanese, including the right to station and transport troops
through Indo-China, the use of selected airfields, and the evacuation of a
hard-pressed Japanese division fighting in China through the port of Haiphong.
An appeal to the Americans for help was poorly received.
Aware of his predecessorà¦¡te, Decoux hesitated, signing the agreement just
before the Japanese ultimatum ran out. The Japanese division was tired of
waiting, however, and proceeded to cross the border on September 22, 1940,
attacking the Tonkinese cities of Dong Dang and Lang Son with tanks and
infantry. The Japanese navy made landings along the coast, Haiphong was bombed,
and the Japanese Air Force flew repeatedly over Hanoi. The Japanese offensive
came as a shock to some senior French officers, who still believed in natural
European superiority and often talked about taking tough action against the
Japanese. Dong Dang fell immediately, and Lang Son fell two days later, with
many of the locally raised colonial units breaking and running before their
first experience of artillery and disciplined infantry attacks carried out by
veteran soldiers. French intelligence had reported that the Japanese were
demoralized, but it was the French who collapsed under pressure. Local
villagers revealed French positions to the Japanese, French artillery fired on
French positions, ammunition ran out quickly, and over a thousand Indo-Chinese
A statement issued by the Japanese emperor on October 5 called the Lang Son
attack unfortunate but not important. The French prisoners were released, but
200 German legionnaires who had been separated from the other French prisoners
were not released until the 13th of October. The pursuing Chinese army made
numerous forays across the frontier, and the French administration remained
fearful of a full-scale Chinese invasion until the end of the war. The French
had lost 800 men in two days of battle with the Japanese.
The fall of Lang Son had almost immediate consequences for French rule.
Discontented locals had witnessed how easily an Asian army defeated the whites.
Vietnamese nationalist Tran Trung Lap was able to raise some 3,000 men in the
Lang Son region, many of them deserters from the Indo-Chinese units defeated by
the Japanese. Their arms were provided from French stocks captured by the
Japanese. The returning French demonstrated they could still deal with a poorly
trained rabble, and quickly drove the revolutionaries into the mountains, where
planes and artillery hammered them. Tran Trung Lap was ambushed, and though he
escaped the massacre of his men by machine-gun, he was shortly after captured
and executed at Lang Son in December.
In the south of Vietnam, then known as Cochin China, an even more dangerous
rebellion broke out in late November. Thai troops had begun to deploy along the
Cambodian border and most of the garrisons in Cochin China had been sent to the
frontier. Fighting broke out in the My Tho region and French police found
themselves overwhelmed. The rebellion spread to Saigon and a number of southern
provinces. A battalion of the Foreign Legion and a battalion of Tonkinese
colonial troops on their way to Cambodia were diverted to the south and, with
the help of artillery, air and naval detachments, quickly repressed the
rebellion with utmost ruthlessness. The French had made their point, and could
now send their forces west to deal with the Thais.
War with Thailand
The French now had to deal with a growth of militarism and Thai nationalism in
neighbouring Thailand (the name was changed from Siam in 1938). Just as Germany
sought to regain the territories lost in the Treaty of Versailles, Thailand was
eager to retake the ethnic Thai lands along the Mekong River it was forced to
cede to the French colony of Laos in 1904. In 1907 the French had also forced
Siam to cede the largely Khmer provinces of Siemreap, Sisophon and Battambang
to French Cambodia. The pro-Japanese government of Marshal Pibul Songgram
sensed an exploitable weakness in the now isolated French colony, and began a
military campaign to retake these territories after the French rejected demands
for their return in October 1940.
The Thais had signed a non-aggression pact with the French in June 1940, but
failed to ratify it after the collapse of metropolitan France. By October
Marshal Songgram had mobilized 50,000 troops (in five divisions) and obtained
100 modern fighters, bombers and seaplanes from Japan. The Thai air-force was
now three times the size of that available to the French, with the new aircraft
added to the 100 American planes obtained between 1936 and 1938 (mostly Vough
Corsairs and Curtiss Hawks). The Thai navy had also been equipped with modern
ships and outclassed the French colonial fleet on paper at least. Border
skirmishes began in November and the Thais crossed the Mekong in December.
Hard-pressed elsewhere, the French could only commit fourteen battalions to the
defence of Battambang Province.
On January 5, 1941, the Thais launched a full attack with artillery and aerial
bombardment of French positions. The Thai offensive covered four fronts:
1) North Laos, where the Thais took the disputed territories with little
2) South Laos, where the Thais crossed the Mekong by the 19th of January
3) The Dangreks Sector, where confused fighting went back and forth
4) Colonial Route 1 (RC 1) in Battambang province, where the heaviest fighting
The initial advance on the RC 1 was repulsed by the Cambodian Tirailleurs
(riflemen). The main Thai column ran into a French counter-attack on January
16, colliding with the French at Yang Dam Koum in Battambang. The Thai force
was equipped with Vickers 6-ton tanks while the French lacked any armour. The
French counter-offensive had three parts:
1) A counter-attack on the RC 1 in the region of Yang Dam Koum
2) An assault by the Brigade dî®¡m-Laos on the islands of the Mekong River
3) Operations by the naval â¯µpement occasionnelá§¡inst the Thai fleet in
the Gulf of Siam
The main thrust of the offensive was by Col. Jacomyà¦¯rces along the RC 1.
The attack at Yang Dam Koum was a debacle from the start. The assault forces
consisted of one battalion of Colonial Infantry (European) and two battalions
of é¸¥d Infantryè…µropean and Indo-Chinese). The forest made artillery
operations difficult, French aircraft never showed, leaving the skies to the
Thai air-force, and radio communications were poor. The French transmitted
orders using Morse code, perhaps explaining why the Thais often anticipated
their movements. A complete rout was prevented when the Thais ran into a
battalion of the Fifth regiment of Legion infantry at Phum Pré¡µ. The
legionnaires were hit hard by a Thai armoured assault, but brought up two 25mm
and one 75mm gun for use against the tanks. The motorized detachment of the
11th Regiment of Colonial Infantry reinforced the line, and three Thai tanks
were destroyed, the rest deciding to retire. The diversionary assault on the
Mekong was successful, but the largest battle of the war was to be fought in
the Gulf of Siam.
Naval war in the Gulf of Siam
The French navy was all important in Indo-China, as with any overseas colony.
The modest force had a virtually non-existent role in the great Asian war of
1941-45, being unable to resist either Japanese advances or Allied blockades,
but they were nevertheless to have one great, unexpected battle before meeting
an ignominious end. The fleet in Indo-China was divided into two parts with
separate levels of responsibility. The FNEO was assigned responsibility for the
overall defence of French colonies in Indo-China and the Pacific, while the Marine
Indochine with its river gunboats was responsible for interior
security in Indo-China.
With the land war going badly for the French, it was decided to send the small
French fleet to the Gulf of Siam to engage a Thai naval force supporting the
flank of the Thai advance. The Thai ships had been spotted lying at anchorage
in the Koh Chang islands by a French navy flying boat. The French task-force (or
Groupement occasionel) consisted of the light cruiser Lamotte-Piquet,
the two colonial sloops Dumont dâ¶©lle and Amiral Charner,
and the WW1 vintage gunboats Tahure and Marne.
During the night of January 16 the French ships closed in on the islands,
dividing themselves into three groups to cover the exits from the island group.
On the morning of the 17th the French roared in under cover of the mist to
engage the Thais. The Thai ships included three Italian-built torpedo boats and
the dual-pride of the Thai fleet, the two new Japanese-made armoured coastal
defence ships with 6çµ®s, Donburi and Ahidé¡¼/EM>. The French
were surprised to find both coastal defence ships there, as they expected only
the Ahidé¡¼/EM>, but the Donburi had arrived the day before in a
standard rotation. The French lost the advantage of surprise when an overeager
Loire 130 seaplane tried to bomb the Thai ships. The Thais received the French
with the opening salvoes of the battle at 6:14 AM. The Lamotte-Piquet quickly
inflicted fatal damage on the Ahidé¡¼/EM> with gunfire and torpedoes,
forcing it to run aground. By 7 AM French guns had sunk all three torpedo
The Donburi was spotted attempting to escape through the 200m high
islands and the French cruiser set off in pursuit. The Donburi was set
afire but continued to engage the cruiser and the sloops, which now began to
pour fire into the Donburi. Badly damaged and listing to starboard,
the Donburi eventually disappeared behind an island and the French
broke off. Later in the day the Donburi was taken in tow by a Thai
transport but capsized soon after. Throughout the engagement the French sailors
were impressed by the courage of the Thai sailors under fire.
The French ships were unable to exploit their victory, however, due to the
arrival of Thai Corsairs targeting the Lamotte-Piquet . Fierce
anti-aircraft fire drove off the attacks, and by 9:40 AM the French turned for
home. In a brief but decisive engagement the Thai fleet had been destroyed at
negligible cost to the French. It appeared at the time to be a sudden and
dramatic reversal of French fortunes.
The Japanese had seen enough and accompanied an offer to mediate the conflict
with the arrival of a powerful naval force off the mouth of the Mekong River to
encourage negotiations. A tentative armistice was imposed on January 28, but
Thai provocations on the frontier continued until a formal armistice was signed
aboard the Japanese battleship Natori off Saigon. The extent of
Thai-Japanese collaboration was revealed when a Japanese-imposed treaty between
Vichy and Thailand was signed on May 9, 1941. The disputed territories of Laos,
part of the Cambodian province of Siem Ré¡° and the whole of Battambang were
awarded to Thailand. The conflict had cost the French over 300 men and a
further loss of prestige amongst its colonial subjects. European troops and
material losses could not be replaced due to the blockade. The French garrison
remained highly demoralized until the Japanese coup in 1945 destroyed the Vichy
colonial army in Indo-China.
In the end the Thais fared little better. The Khmers largely evacuated the lost
Cambodian territories, preferring French rule, and Thailand itself was soon
occupied by its more powerful ally, the Japanese. American Flying Fortresses
bombed Bangkok in 1942. The Thais declared war against the allies in 1944, but
there was some confusion over whether the declaration was actually delivered to
the US government, and after the war the Thai government certified the
declaration of war as null and void. The uncomfortable affair was mutually
forgotten. The disputed territories in Laos and Cambodia were returned to the
new Gaullist government at the end of the war.
The French light cruiser Lamotte-Piquet was laid up shortly after the
battle of Koh Chang due to the shortage of fuel. In 1945 the ship was bombed by
American planes before being scuttled during the brutal Japanese coup of March
1945. The remaining naval force continued to escort convoys up and down the
Vietnamese coast as best they could from 1941 to 1945. In their sudden seizure
of Indo-China, the Japanese sank a number of French ships with shore fire,
while the remainder were scuttled by their crews, who were then imprisoned. The
French colonial armed forces in Indo-China had ceased to exist by the time the
British and Chinese armies arrived after the Japanese surrender. It was the
British and Chinese, rather than the men of Vichy, who would turn over the
colony to Gaullist France at the end of World War II.
Show Footnotes and
Possibly out of Print:
La Marine Franç¡©se en Indochine, 1939-1955, Tome 1, Service historique de la
Marine (Paris), 1991.
dìº¯n, Claude Hesse: La Pré³¥nce militaire Franç¡©se en Indochine, 1940-1945,
Service historique de l/Armé¥ de Terre, Vincennes, 1985, croquis no.6.
The War in Indochina: 1945-54.
The French Navy in Indochina: Riverine and Coastal Forces, 1945-54.
The Indochinese Experience of the French and the Americans: Nationalism and
Communism in Cambodia, Laos, and Vietnam.
Copyright â°°2 Andrew McGregor.
Written by Dr. Andrew McGregor. If you have questions or comments on this
article, please contact Andrew McGregor at:
About the author:
Andrew McGregor is director of Toronto-based Aberfoyle International Security (AIS) and former senior editor of the Global Terrorism Analysis Program
of the Washington DC based Jamestown Foundation. He received a Ph.D. from the University of Toronto’s Department of Near and Middle Eastern
Civilizations in 2000 and is a former Research Associate of the Canadian Institute of International Affairs. He is the author of an
archaeological history of Darfur published by Cambridge University in 2001. His latest book is A Military History of Modern Egypt,
published by Praeger Security International. Dr. McGregor has written over 700 articles on international military and security issues
for organizations including Jane’s Intelligence, the Royal Institute of International Affairs and the Canadian Institute of Strategic Studies.
He also provides frequent commentary on military and security issues for international newspapers, radio and television, including the
New York Times,
Financial Times, CNN, Fox News, al-Jazeera, the CBC and the BBC. He can be reached at firstname.lastname@example.org, or visit the AIS website at
Published online: 11/16/2002.
* Views expressed by contributors are their own and do not necessarily represent
those of MHO.