The Battle of Ko Chang

At dawn on 17 January 1941 a French naval force from French Indochina – the old light cruiser Lamotte-Picquet and four sloops – steamed in among the islets off the southern tip of Ko Chang island in the eastern part of the Gulf of Thailand. At anchor lay ships of the Royal Thai Navy: the modern Japanese-built coastal defence ship Thonburi and two torpedo boats. Their crews were asleep. In less than two hours both torpedo boats had gone to the bottom, and the burning Thonburi, her captain dead, had taken refuge in the shallows at a river mouth and run aground there. The French lost no ships and returned to their base at Saigon.

It was the most important naval battle of the Franco-Thai War, a short conflict at the turn of 1940 and 1941 in which the Thailand of Prime Minister Plaek Phibunsongkhram tried to wrest territory in Laos and Cambodia from a weakened Vichy France. The battle is often called a “decisive victory” for the French. At sea the victory was indeed complete, but it did not decide the war. Two weeks later the fighting was halted by an armistice imposed by Japan, and the peace concluded in Tokyo in May 1941 gave Thailand most of the territory it had demanded before the war. The real winner turned out to be Japan.

The lost territories

The dispute went back to the end of the 19th century. During the crisis of 1893, when French gunboats sailed up the Menam (Chao Phraya) river towards Bangkok, Siam had to cede to France the lands on the left bank of the Mekong, which became part of French Laos. Treaties of 1904 and 1907 took further territories: strips on the right bank of the Mekong and the western provinces of Cambodia, with Battambang and Siem Reap, where the ruins of Angkor stand. King Chulalongkorn gave way in order to preserve the independence of his country, the only one in South-East Asia not to become a colony. In Thai memory these losses remained a humiliation, and school maps of the 1930s marked them as “lost territories”.

After the coup of 1932, which ended absolute monarchy, the army played an ever greater role in Siam. In December 1938 General Plaek Phibunsongkhram, known as Phibun, leader of the military wing of the revolutionaries and an admirer of Benito Mussolini, became prime minister. His government preached a nationalism which its chief ideologue, Luang Wichitwathakan, extended to all the Tai peoples, including those living in Laos, Burma and southern China. In June 1939 Siam adopted the name Thailand, the land of the Thai people as a whole and not merely of the inhabitants of the old kingdom. The name was also a programme.

The fall of France provided the opportunity. On 12 June 1940 Thailand signed non-aggression pacts with France, Britain and Japan. After the armistice with Germany, Bangkok made ratification of the pact with France conditional on a border adjustment: it demanded that the frontier follow the main channel of the Mekong and that the lands on the river’s right bank be returned, and also an assurance that if France lost Indochina, Laos and Cambodia would revert to Thailand. The government of Marshal Philippe Pétain refused. Meanwhile, in September, Japan had forced the French to admit its troops into Tonkin, and the Governor-General, Admiral Jean Decoux, had given way after brief fighting at Lạng Sơn. In Bangkok it was concluded that France would not fight. In October great demonstrations of students and civil servants marched through the capital demanding the recovery of the lost lands, and Phibun addressed them in front of the Ministry of Defence.

War on the Mekong

From the autumn there were exchanges of fire and violations of airspace along the border, and at the end of November 1940 the conflict turned into an undeclared war. Both sides bombed each other’s border towns and airfields. Here Thailand had the advantage. Its army numbered some 60,000 men and had light tanks and tankettes, while its air force had around 140 front-line aircraft, including American Curtiss Hawk fighters and Mitsubishi Ki-30 light bombers recently bought from Japan. Thai aircraft bombed Vientiane, Sisophon and Battambang in daylight. The French forces in Indochina, some 50,000–60,000 men, three-quarters of them locally recruited, had just been beaten by Japan; they had obsolete weapons, about twenty old Renault FT tanks and a handful of aircraft, and could receive no reinforcements from France. Decoux later admitted that the Thai pilots flew like men with combat experience.

At the beginning of January 1941 (most accounts give 5 January, some 6 or 10 January) the Burapha and Isan Armies launched an offensive in Laos and Cambodia. In Laos the Thais occupied the disputed lands on the right bank of the Mekong without much resistance. In western Cambodia French resistance was stiffer. On 16 January the French mounted the largest counter-attack of the war: a battle group built around a battalion of the 5th Foreign Infantry Regiment of the Foreign Legion attacked the villages of Yang Dang Khum and Phum Préav in Battambang province. The attack, poorly coordinated and launched without reconnaissance, broke down against fortified positions, and the French had to withdraw. The Thais, however, were unable to follow them up, since their tanks were halted by French artillery fire. The front in Cambodia fell quiet.

The Groupe occasionnel

On land the French could not win, but at sea they had a chance. Decoux, himself an admiral, had on 9 December 1940 formed at Cam Ranh Bay an “occasional group” (Groupe occasionnel) made up of almost everything that sailed under the French flag in the Far East. Its core was the light cruiser Lamotte-Picquet of the Duguay-Trouin class, built in the mid-1920s: fast and armed with eight 155-millimetre guns, but almost entirely without armour. She was accompanied by two modern colonial sloops of the Bougainville class, Dumont d’Urville and Amiral Charner, with 138-millimetre guns, and two old sloops from the First World War, Tahure and Marne. The force was commanded by Captain (capitaine de vaisseau) Régis Bérenger, the cruiser’s captain. It had no fighter cover; reconnaissance was carried out by a few Loire 130 seaplanes from the base at Réam in Cambodia.

The Royal Thai Navy, expanded in the 1930s, was on paper the more modern force. It had two coastal defence ships built in Japan in 1938, Thonburi and Sri Ayutthaya, displacing about 2,300 tons and each armed with four 203-millimetre guns in two turrets, as well as a dozen or so torpedo boats, most of them from Italian yards, gunboats and four small Japanese-built submarines. What it lacked, however, was training, particularly among its gunners, and efficient communications.

On 13 January Decoux ordered the naval commander in Indochina, Rear Admiral Jules Terraux, to strike at the Thai fleet in support of the counter-attack on land. The order was simple: attack the Thai coast from Rayong to the Cambodian border in order to force Bangkok to withdraw its troops from Cambodia. The ships met on the afternoon of 15 January near the Poulo Condore islands and that evening set off across the Gulf of Thailand at 14 knots, the most the old sloops could manage. On 16 January a reconnaissance seaplane spotted a coastal defence ship and a torpedo boat off Ko Chang, and at the main base of Sattahip a gunboat, several torpedo boats and the submarines. Bérenger chose the weaker and nearer target: the sloops would have reached Sattahip only in daylight, by which time surprise would have been lost.

Dawn off Ko Chang

The anchorage south of Ko Chang was surrounded by high, wooded islets with several channels between them. Bérenger divided his force into three groups so as to close the escape routes: Lamotte-Picquet headed for the eastern part of the anchorage, where the largest ships were expected, Dumont d’Urville and Amiral Charner for the centre, and Tahure and Marne came in from the west. At about 5.45 a.m. the groups separated. The sea was calm; sunrise was due at 6.30.

The final reconnaissance brought a surprise. The seaplane that flew over the anchorage at about 6.05 reported not one torpedo boat but two: during the night the torpedo boat Chonburi had arrived to relieve Chanthaburi, which was due to return to base, and Songkhla lay alongside. The airman tried to bomb the ships but was driven off by anti-aircraft fire, and the Thais were alerted. Steam was hurriedly raised on the torpedo boats. But it was too late. Under fire from the cruiser and the sloops, both torpedo boats, motionless or just getting under way, caught fire and sank before 7 a.m. Accounts differ as to which ships scored the decisive hits: some credit Lamotte-Picquet, others the sloop Dumont d’Urville.

At about 6.40 Thonburi was sighted from the cruiser, steaming north-west. An exchange of fire began at a range of about 10 kilometres, hampered by islets that kept hiding the targets. According to Thai accounts, one of the first French salvoes hit the bridge and killed the ship’s captain, Commander Luang Phrom Wiraphan. Thonburi fired rapidly but inaccurately, switching her fire between the cruiser and Amiral Charner, around which 203-millimetre shells were falling. By about 7.15 she was on fire, and a hit had knocked out her after turret. Listing, with her other turret jammed, she managed to reach the shallow water at the mouth of the Chanthaburi river, where the deeper-draught French ships could not follow. At about 7.50 Lamotte-Picquet fired torpedoes at her from long range and lost sight of her behind an island.

At 8.40 Bérenger ordered a withdrawal. It was then that Thai aircraft arrived. Hawk fighters carrying bombs and Corsair biplanes attacked the cruiser several times. The bombs fell close, and according to some accounts one hit the ship but failed to explode. The last raid came at about 9.40. The force returned to Saigon without losing a ship.

The reckoning and two versions

Thonburi, badly damaged, had run aground. The same day the Thai transport Chang took her in tow and beached her in the shallows off Laem Ngop, where the ship capsized onto her side. The torpedo boats Songkhla and Chonburi lay on the bottom. Survivors were picked up by ships that had been lying north of the island and had not been detected by the French: the torpedo boat Rayong, the minelayer Nong Sarai and the patrol vessel Thiew Uthok. The Thai navy officially reported 36 killed, 20 of them from Thonburi. The French, counting the sunk ships with their full crews, estimated enemy losses at as many as 300 men. On the French side, according to naval records, no one was killed, and the ships suffered only light splinter damage.

Both sides exaggerated. French communiqués and some later publications claimed that the torpedo boat Trat had also been sunk, and even the second coastal defence ship, Sri Ayutthaya. Neither had been at Ko Chang. A Thai board of inquiry after the battle, relying on the accounts of sailors and fishermen, maintained for its part that Lamotte-Picquet and other French ships had been seriously damaged, which French logbooks do not confirm. The victory was beyond dispute: at the cost of a few wounded, the French had eliminated about a third of the Thai fleet. Bérenger was promoted to rear admiral. Thonburi was later raised and repaired in Japan, but she never returned to combat service and was used as a training ship. Her turret and bridge stand today as a memorial at the naval academy in Samut Prakan, and in Thailand the battle is remembered as an example of the heroism of a crew that fought to the end.

Japanese “mediation”

The battle improved the position of the French, but it did not change the situation on land, where Thai troops stood in Laos and western Cambodia. It did, however, change the calculations in Tokyo. Japan wanted neither the defeat of Thailand, with which it had plans in mind regarding British Malaya and Burma, nor an excessive weakening of Decoux’s administration, which was obediently handing over bases in Tonkin. The Foreign Minister, Yōsuke Matsuoka, offered mediation, which both sides accepted around 20–21 January, France under evident pressure. A ceasefire came into effect at 10 a.m. on 28 January, although that very morning Thai bombers attacked Sisophon. On 31 January 1941, aboard the Japanese cruiser Natori, lying in the roads off Saigon, representatives of France and Thailand signed a preliminary armistice agreement in the presence of Japanese officers.

Peace negotiations were then held in Tokyo. The Japanese, acting as “mediators”, in practice dictated the terms, and Vichy, with no hope of help, had to give way. The treaty signed in Tokyo on 9 May 1941 awarded Thailand the Laotian lands on the right bank of the Mekong (part of Luang Prabang with Sainyabuli, and part of Champasak) and the Cambodian province of Battambang together with most of Siem Reap; the town of Siem Reap itself and Angkor remained with France. In return Thailand undertook to pay France 6 million piastres. In Bangkok the war was proclaimed a victory, Phibun was promoted to field marshal, and the Victory Monument was erected in the capital. One of the new provinces was named after him.

Its place in the war

Ko Chang was one of the few clear-cut victories of the French navy in the Second World War; some French naval historians even called it France’s last naval victory. It had no effect on the outcome of the war, however. The conflict showed that France was unable to defend its empire in Asia and that any dispute it had would be settled by Japan. Tokyo gained Bangkok’s gratitude, influence in both countries and proof that it could carve up the colonial possessions of the Europeans. According to some historians, Phibun gave the Japanese a verbal assurance of support should they attack Malaya, although he later tried to draw closer to the British and the Americans for fear of a Japanese invasion.

In July 1941 Japan moved into southern Indochina, and the United States, Britain and the Netherlands responded by freezing Japanese assets and imposing an oil embargo. On 8 December 1941 Japanese troops landed in Thailand, which after a few hours of fighting agreed to let them pass through to Malaya and Burma, and soon concluded an alliance with Japan. Thailand had to return the territories gained in 1941 to France in 1946, when Paris threatened to block its admission to the United Nations. In French memory Ko Chang long remained a battle passed over in silence, because it had been won by the Vichy navy, whereas in Thailand it is remembered as the day a small fleet stood up to a European adversary.