Battle of Ko Chang

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Battle of Ko Chang
Part of the Franco-Thai War
Battle of Koh Chang 17 january 1941 (English version).svg
A map of the battle of Ko Chang
Date 17 January 1941
Location Gulf of Thailand
Result Decisive Vichy French victory

France Vichy France

Thailand Thailand
Commanders and leaders
France Régis Bérenger Thailand Luang Phrom Viraphan 
1 light cruiser
4 avisos
9 aircraft
1 Coastal defence ship
2 torpedo boats
Casualties and losses
1 light cruiser damaged ~36 killed
2 torpedo boats sunk
1 coastal defence ship grounded

The Battle of Ko Chang took place on 17 January 1941 during the Franco-Thai War and resulted in a decisive victory by the French over the Royal Thai Navy. During the battle, a flotilla of French warships attacked a smaller force of Thai vessels, including a coastal defence ship.

In the end, Thailand lost two ships sunk and one heavily damaged and grounded. Within a month of the engagement, the Vichy French and the Thais negotiated a peace which ended the war.


Thai Navy[edit]

The Royal Thai Navy had been modernized with the recent acquisition of vessels from Japan and Italy. The major units of the fleet included two Japanese-built armoured coast defence vessels, which displaced 2,500 long tons (2,500 t) and carried 8-inch (203 mm) guns, two older British-built armoured gunboats with 6-inch (152 mm) guns, 12 torpedo boats, and four submarines.

In addition, the Royal Thai Air Force had in its inventory over 140 aircraft, including relatively modern Mitsubishi Ki-30 (Allied reporting name "Ann") light bombers, which saw extensive service against the French. These aircraft in themselves were quite capable of causing severe damage to any French naval mission which might be mounted. Other less capable aircraft in the Thai inventory included P-36 Hawk fighters , 70 Chance-Vought O2U-2 Corsair biplanes, six Martin B-10 bombers and several Avro 504 trainers.

French Navy[edit]


Despite the strength of the Thai forces, the French Governor General of Indochina and Commander-in-Chief Naval Forces, Admiral Jean Decoux, decided the naval attack should go ahead. A small squadron called the Groupe Occasionnel was formed on 9 December 1940 at Cam Ranh Bay, north of Saigon, under command of Capitaine de Vaisseau Régis Bérenger.

The squadron consisted of the light cruiser La Motte-Picquet, the avisos Dumont d'Urville PG 77 and Amiral Charner PG 81|2, and the older avisos Tahure and Marne. There was no air cover except for eight Loire 130 seaplanes based at Ream, which provided reconnaissance. Additional scouting was done by three coastal survey craft, and intelligence gleaned from local fishermen.

Bérenger's squadron began training manoeuvres in Cam Ranh Bay shortly after assembling. On 13 January 1941, Admiral Decoux formally requested Bérenger to send the squadron against the Thais to support of a land offensive planned for 16 January. The land operation was intended to force back Thai forces that had been advancing along the coast. Because of the disparate speeds of the French ships, Bérenger sent the slower sloops on ahead, while he remained in Saigon to complete the final elements of the plan.

Several options were being prepared, the Admiralty in France having given its formal blessing to use naval forces in support of the army. The final planning meeting on the 13th saw an immediate delay in the execution of the operation for 24 hours. Once the plans were finalised, Bérenger sailed in Lamotte-Picquet. The delay in the start of the operation allowed him to refuel at Cape St. Jacques before his rendezvous with the slower ships at 16:00 on the 15th, 20 mi (17 nmi; 32 km) North of Poulo Condore.

Admiral Decoux's order were simple: "Attack the Siamese coastal cities from Rayong to the Cambodian frontier to force Siamese government to withdraw its forces from the Cambodian frontier". On the evening of the 15th, following a final conference on board the flagship, the squadron weighed anchor at 21:15 and closed the Thai coast at 14 kn (16 mph; 26 km/h), the top speed of the sloops. The French ships remained undetected as they entered the Gulf of Siam, but their quarry was not as fortunate. The Loire 130s from Ream had completed a sweep of the coast from Trat to Sattahip. They had located one coast defence ship and two torpedo boats at Koh Chang, and one gunboat, four torpedo boats, and two submarines at Sattahip.

Their report was forwarded to Marine Headquarters in Saigon, who re-transmitted it to the Lamotte-Picquet. Bérenger considered his options and decided on a dawn attack on the Thai ships at Koh Chang. He ignored Sattahip because the sloops would not be able tto reach it until later in the day, when the element of surprise would already have been lost. Also, the strength of the harbour defences at Sattahip could was unknown. The Thai Navy force at Koh Chang was weaker and offered the best chance of victory.

Bérenger decided his squadron would approach Koh Chang at dawn from the southwest. Because the anchorage at was surrounded by islands and islets, many over 200 metres (656 feet) high, the squadron would separate and use the cover of the islands to concentrate fire on portions of the Thai squadron, while also covering all the avenues of escape. The easternmost channel was the most likely route by which a breakout would be made; it was the most suitable route and also the area where the reconnaissance had placed the largest Thai ships. The Lamotte-Picquet would head to the eastern side of the anchorage to block the route, while the sloops blocked the center and pounded the Thai ships there. The smaller French ships would concentrate to the west.


Amiral Charner

The French squadron closed on the anchorage at 05:30 on 17 January. At 05:45, they split into the three groups as planned, Lamotte-Picquet heading for the eastern part of the anchorage, Dumont d'Urville and Amiral Charner continuing to the central position and Tahure and Marne heading for the western side. Conditions were perfect—the weather was fine, the seas calm and almost flat. Sunrise was due at 06:30, and the scene was lit only by the first rays of light on the horizon and by the dim moonlight.

A final aerial reconnaissance of the target area had been arranged using one of the Ream-based Loire 130s. Lamotte-Picquet carried two such aircraft, but these could not be launched due to catapult problems. At 06:05, the Loire 130 overflew the anchorage and reported two torpedo boats. This came as a nasty surprise to the French; previous reports led them to believe that only one was present, but during the night the HTMS Chonburi had arrived to relieve Chantaburi, which was to return to Sattahip later that day for repairs.

Once their presence had been passed to Lamotte-Picquet, the aircraft attempted an attack using bombs, but it was forced off by a heavy barrage of anti-aircraft fire. The effect of this mission was double edged. The French were now aware of what they faced, but the element of surprise had been wasted and there was still thirty minutes until sunrise. Caught napping by the oncoming French, the Thais desperately began to raise steam and prepared to slip their anchors. However, both torpedo boats were sunk by gunfire from Lamotte-Picquet.

At 06:38, lookouts on Lamotte-Picquet spotted the coastal defence ship HTMS Thonburi heading northwest, at a range of 10,000 meters (10,936 yards). A running battle ensued, with the fire of both ships frequently blocked by the towering islets. The fire from the Thai ship was heavy, but was inaccurate. By 07:15, fires could be seen on Thonburi, which then found herself engaged not only by the cruiser but also by the sloops. In the beginning of the engagement, a lucky shot from Lamotte-Picquet killed the captain of Thonburi, Commander Luang Phrom Viraphan, and disrupted her operations. Believing they had a better chance of hurting the smaller French ships, the Thais shifted their fire onto Admiral Charner, which soon found 8-inch (203 mm) salvoes falling around her.

Thonburi shifted fire back to Lamotte-Picquet after a salvo from the French cruiser put her after turret out of action. She soon reached the safety of shallow water which the French ships could not enter for fear of grounding, but it was too late for the hapless Thais, as Thonburi was burning fiercely and listing heavily to starboard. Her remaining turret was jammed and could not fire unless the manoeuvres of the ship put it in an appropriate position. At 07:50, Lamotte-Picquet fired a final salvo of torpedoes at 15,000 meters (16,404 yards) but lost sight of Thonburi behind an island from which she was not seen to emerge.

At 08:40, Bérenger ordered the squadron to head for home, but this coincided with the start of the expected Thai air attacks. Thai planes dropped several bombs close to Lamotte-Picquet and scored one hit, but the bomb failed to explode. Lamotte-Picquet‍ '​s anti-aircraft guns put up a vigorous barrage and further attacks were not pressed home. The final raid departed at 09:40, after which the victorious French squadron returned to Saigon.


A plaque commemorating the battle

The French left behind them a scene of total devastation. Thonburi was heavily damaged and grounded on a sand bar in the mouth of the Chanthaburi river, with about 20 dead. She was later raised and repaired by the Japanese, survived the war and was used as a training ship until she was retired. The Thai transport HTMS Chang arrived at Ko Chang shortly after the French departed and took Thonburi in tow.

The torpedo boat Chonburi was sunk with a loss of two men and HTMS Songhkla sank with a loss of fourteen dead. The survivors were rescued by the torpedo boat HTMS Rayong, the minelayer HTMS Nhong Sarhai and the fishery protection vessel Thiew Uthok. These three ships, which had been sheltering to the north of Ko Chang, wisely chose not to break cover and thus were not spotted by the French. The French were elated, for they had inflicted a defeat as decisive in its way as the Japanese at Tsushima, and had not suffered losses of significance.

Their success is all the more notable when the difficulties of navigating and fighting in such confined waters are considered, and given the courage and tenacity which the Thai sailors exhibited during the action, a fact which the French were gracious to acknowledge. In the end, it was all for nought. Five days later the Japanese government offered to arbitrate in the search for a peaceful settlement, and it soon confirmed the Thai annexations. Even this state of affairs did not last for long, as Thailand was invaded by Japanese forces later that year during the attacks on Malaya, and at the end of World War II was forced to return her short-lived gains to France.

The Thonburi was later raised by the Royal Thai Navy. She was repaired in Japan and was used as a training ship until she was finally decommissioned. Her guns and deck are preserved as a memorial at the Royal Thai Naval Academy, Samut Prakan.

During the post-action investigations, the Thai navy claimed, based on claims by Thai sailors and the fisherman around Ko Chang, that heavy damage was seen to have been caused to Lamotte-Picquet and her squadron. The report claimed the crew of Lamotte-Picquet spent all of the following night repairing the damage, though it is not told how the French ships supposedly were observed after their departure from the site. Such claims are unsubstantiated and are not reflected in any French documentation, nor in the ships logs.

See also[edit]


  • J. Guiglini (trans. K Macpherson) 'A résumé of the Battle of Koh Chang' Warship International 1990 No.2
  • Romé, Contre-Amiral Paul, Les oubliés du bout du monde: Journal d'un marin d'Indochine de 1939-1941 1998. Danclau, Dinard, France
  • (French) La bataille de Koh Chang,
  • Battle of Ko Chang

Coordinates: 12°00′04″N 102°27′04″E / 12.001°N 102.451°E / 12.001; 102.451