Franco-Thai War 1940-1941

Thailand responded pragmatically to the military and political pressures of World War II. French Indochina and Thailand had unresolved territorial disputes in Laos and Cambodia but in June 1940 Thailand intent on avoiding direct involvement in war signed non-aggressions pacts with Britain and Japan as well as France. However, after the French were defeated in battle by the Germans later that month, Thailand lost interest in ratifying its treaty with Vichy France. The somewhat pro-Japanese Thai government took the opportunity presented by French weakness to pressure its government, diplomatically and if necessary militarily, to make territorial concessions. Thai armed forces were mobilized in October. It is likely that the first Thai incursions into French Indochina took place on November 23, 1940 while the French forces were distracted by an uprising in Cochin China.

Several skirmishes took place between French and Thai troops patrolling in the disputed territories during November and December. There were also reports of both sides conducting air and artillery strikes across the border. Thai forces began an offensive into Cambodia and Laos on January 10, 1941 but French and colonial troops offered strong resistance and launched a counter-offensive about January 16th which failed to make significant progress. While the ground war appeared to be a stalemate, the French were preparing to strike at the Thai navy. On January 17th, the small French squadron surprised the Thai at Koh Chang, capsizing one old battleship, setting a second on fire and sinking two torpedo boats before withdrawing unscathed. The highest casualties of this undeclared war were probably suffered by the Thai navy in this 90-minute action. The war seemed set to continue but Japan applied diplomatic pressure on the Vichy French, threatening to intervene on the side of Thailand. Both sides agreed to a ceasefire on January 28, 1941.

In March, Vichy France was pressured by not only Japan but Germany to accept Japanese mediation of the dispute with Thailand. The mediation resulted in a treaty which transferred to Thailand control of three Cambodian and two Laotian provinces west of the Mekong River. In a matter of months, Thailand would then be forced to accept the Japanese troops on its territory. In September 1945, after end of World War II, France forced Thailand to return the territory gained through this war.

Notes

[1] Clodfelter reports total French casualties of about 200 in his 2017 revision. Several other sources suggest neither French nor Thai losses exceeded 400 battle deaths.

References

Clodfelter, 669; COW145; Thailand - A Country Study.

Region

East Asia

Belligerents

France, Thailand

Dispute

Territory

Initiation Date

December 1, 1940

Termination Date

January 28, 1940

Duration

1 month, 28 days
(59 days)

Outcome

Imposed Settlement
(Japanese intervention)

Fatalities

Total: 1,400
France: 700^[1]
Thailand: 700

Magnitude

3.1

Armed Conflict Events Data