The Franco-Thai War (1940-1941) opposed the Thailand of General Plaek Pibulsonggram, better known as Phibun, and France of Vichy in the Indochinese peninsula.
After the French rout of 1940, Thai Prime Minister Phibun saw a chance for Thailand to recover the territories abandoned to France during the reign of Chulalongkorn (provinces of Melou Prei and Tonlé Repou in 1904, and provinces of Battambang, Sisophon and Siem Reap in 1907, all attached to Cambodia), and to avenge the humiliations suffered in 1893 (attachment of Laos to French Indochina) and 1904.
The weakening of the metropolis made the maintenance of French control over Indochina risky and difficult. The colonial administration, deprived of aid and reinforcements, had been forced to authorize the Japanese to settle in French Indochina after the capture of Lang Son (offensive of September 22-25, 1940). The weak French resistance to this invasion convinced the Phibun regime that a military confrontation would turn to its advantage.
Triggering and operations
After nationalist and anti-French demonstrations in Bangkok, border skirmishes follow one another along the Mekong. The numerically superior Thai air force bombed Vientiane, Sisophon, and Battambang by day with impunity. French air forces attempt retaliatory raids, but damage to Thailand is much less. Admiral Jean Decoux, Governor General of Indochina, recognizes that Thai airmen flew like men with several campaigns to their credit. In December, Thailand occupies Pak-Lay and Bassac.
At the beginning of January 1941, the Burapha Thai and the Isaan armies launched an offensive on Laos and Cambodia. French resistance was immediately in place, but many units were outmatched by the better equipped Thai forces. The Thais quickly occupy Laos, while in Cambodia the French resistance is better.
On January 16, 1941, France launched a broad counter-offensive on the Thai villages of Yang Dang Khum and Phum Preav, where the fiercest fighting of the war took place. The French counter-attack is cut to pieces, and ends in a retreat, but the Thais cannot pursue the French forces, their tanks having been pinned down by the French artillery.
Battle of Koh Chang
While the situation on land was critical for France, Admiral Jean Decoux (1884-1963) authorized Admiral Terraux, commander of the Navy in Indochina, to carry out an operation against the Thai Navy.
The order is given to available warships to attack in the Gulf of Thailand. An aerial reconnaissance was carried out on January 16 at Satahib (eastern tip of Bangkok Bay) and at Koh Chang.
On the morning of January 17, 1941, the "occasional group", a fleet of circumstances formed by the cruiser Lamotte-Picquet, the colonial sloops Dumont d'Urville, Admiral Charner and the sloops Marne and Tahure, placed under the command of the captain Régis Bérenger , commanding the cruiser Lamotte-Picquet, attacks Thai battleships and torpedo boats at Koh Chang.
Although the enemy fleet outnumbered it - by far - the French navy operation, carried out brilliantly, ended in complete victory. At the end of the fight, which lasts almost two hours, the balance sheet is heavy on the Thai side. The torpedo boats Chomburi and Songkla are sunk. The coast guard battleship Dombhuri capsizes, in flames. A good part of the Thai war fleet is destroyed.
More than 300 men died on the Thai side and there are barely 80 survivors.
This is an important victory.[1] Moreover, the Battle of Koh Chang on January 17, 1941 was the last naval battle won by France (in fact, the only naval victory won by France in the two world wars).
However, on January 24, the final aerial battle took place when the French airport of Angkor was hit by a raid by Thai bombers.
The war left about 3,400 dead.
Japan, eager to secure Thailand's military cooperation, quickly intervened as a mediator in the conflict. An ultimatum first imposes an armistice on the two belligerents, proclaimed on May 28. On May 9, France, under Japanese constraint, signs a peace treaty, by which it abandons the provinces of Battambang and Siem Réap (literally "Siamese law") ), taken in Cambodia, Champasak and Sayaburi (taken in Laos). This treaty is followed by another between France and Laos on August 21. The protective power of Cambodia and Laos could not protect them.
This annexation led to the cessation of oil deliveries from the United States to Japan (April 1941) and the creation, by the Anglo-Saxon secret services, of Thaï Séri (Free Thais), a clandestine anti-Japanese organization. After Pearl Harbor, the people and the Thai assembly mobilize against Japan, which attacks it. After the short campaign concluded with the Battle of Prachuab Khirikhan, Thailand allied with Japan.