Koh-what? A World War II naval battle you probably never heard of.

The Dhonburi in action "against French imperialism"

World War II was a frustrating experience for the French Navy. Equipped with well-designed, modern and efficient ships; manned by well-trained and professional crews and well-prepared for the tasks it would been given, the army's defeat and national capitulation neutralized the fleet for most of the war. The navy's largest battles ended up being against its former allies in various African ports. French naval forces acquitted themselves honorably, but without enthusiasm. And most of the fleet ended up being sunk at the hands of its own crews at Toulon. But for one brief moment a small French flotilla had a chance to show its stuff against an opponent and suggest how well the fleet might have done if given a chance. On Jan. 17, 1941 in Koh-Chang Bay in the Gulf of Siam a French squadron destroyed the pride of the Thai Navy during the brief war between that Japanese client state and Vichy-ruled France.

Dhonburi

Involving ten ships and a total tonnage over 17,000, the battle was a surprisingly evenly matched contest that had a very lopsided outcome. Many accounts assume that the result was foreordained, pointing out the obvious size difference between the main French ship involved, the 7.000-ton light cruiser Lamotte Picquet and the 2,265-ton Thai coast defense ships Sri Ayuthia and Dhonburi (often spelled Thonburi). But as wargamers know, size or numbers are not all that matters in warfare. The battle was fought around dawn on Jan. 17th as the French flotilla, comprised of the Lamotte Picquet and four gunboats, sought out the main units of the Thai Navy, two coast defense "battleships" and three torpedo boats, which were anchored at Ko-Chang. The Thai force was actually a bit larger than the French expected, but the French had the benefit of some aerial support in the form of a float plane and had a good idea of what they were facing. The Thai force, on the other hand, was caught by surprise.

Battle of Ko Chang Scenario chart from Atlantic Navies

The action can be divided into two parts, the engagement between both sides' light forces and the duel between the French cruiser and the larger Thai units. The light force fight was a mismatch. The Thai force was comprised of three torpedo boats of the Italian-built Puket class. These weren't small PT-boats but were in the European tradition of small torpedo craft dating back to World War I, with a displacement of 318 tons, although these were new ships, built in the late 1930s. While armed with three 12-pounder guns suitable for fighting similar craft, their real striking power resided in six 18-inch torpedoes. Puket class shown at right. Opposing them were four gunboats, termed colonial sloops by the French, which were older, slower, larger and relied completely on their guns for combat power. The two smaller ships, the Tahure and Marne were second class sloops not much bigger than the Thai torpedo boats, displacing 644 tons and 570 tons respectively and built during World War I. The Tahure had a pair of 5.5-inch guns while the Marne had four 4.1-inch guns. The other two French gunbats were much more formidable and modern (1933) vessels of the Bouganville class, displacing 1,965 tons (destroyer-sized) and carrying three 5.5 guns. Named the Dumont D'Urville and the Amiral Charner, these were termed first-class sloops by the French. The smaller pair of sloops moved inshore between the islet of Koh Kra and Koh Chang to attack the three torpedo boats anchored off Koh Chang, while the larger pair of sloops came in from the other side of the anchorage. This was potentially a risky move. If the Thai torpedo boats had been alert and prepared they could have concentrated against one of the French forces with a concentrated torpedo attack. But the Thai boats were neither alert nor prepared and the French pincer simply closed an inescapable trap. One of the Thai torpedo boats was hit by an early shot from the French cruiser as it steamed by on its way to deal with the larger Thai ships and was set ablaze. The other two torpedo boats were able to get underway. It did them little good, though, as all four French ships blazed away and eventually both torpedo boats were also set afire. No French ship was hit and accounts make no mention of the Thai boats launching any torpedoes.

Lamotte Picquet in 1939

On the other side of the spit of land dividing the bay the Lamotte Picquet engaged the two Thai coast defense ships. This was potentially a much more even fight. The Lamotte Picquet was a member of the Duguay-Trouin class of light cruisers. Built in 1926, it was armed with eight 6-inch guns and a dozen 21-inch torpedoes, and lightly armored. It displaced 7,249 tons, which at first glance would seem to indicate it far outclassed the two Thai vessels, but as a light cruiser for a major power it had to devote a lot of design displacement to things such as endurance, habitability and speed. In contrast, the two Thai vessels, as coastal defense vessels, could concentrate their design resources on armor and firepower, with the minimum devoted to fuel, crew comfort or speed. While having the tonnage of a large destroyer, the coast defense ships were armed and armored at levels more typical of heavy cruisers. Each ship was armed with a pair of 7.9-inch guns, so the pair was roughly equivalent in potential combat power to a heavy cruiser. In the actual event, however, the Thai ships were defeated rather handily by the French cruiser. The Sri Ayuthia was hit by a torpedo from the Lamotte Picquet and several shells early in the action, just as it was getting underway. It ran aground and was abandoned. The other Thai "battleship" (which is what the Thais called them) engaged the Lamotte Picquet in a running fight but once again the Thai gunners were unable to score while the French landed some damaging blows, including one that killed the Thai ship's captain. The Thonburi hit a reef and sunk. Later it was salvaged and the conning tower and one turret are now preserved as a memorial in Thailand. The Battle of Ko Chang provides some interesting lesson in military effectiveness and especially between the parade-ground military establishments of minor powers and real professionalism of major powers. The Thai ships were impressive on paper. They were modern (1938) warships built in Japan, impressively armed and optimized for precisely the kind of battle they found themselves engaged in. But the evidence suggests that the crews were not well-trained, especially in gunnery, as apparently no French ship was hit throughout the battle. In comparison, even though they were on a colonial station, far from home and probably didn't represent the navy's elite crews, the French gunners savaged the Thai ships, hitting all of them multiple times and destroying the entire force. The Battle of Koh Chang is depicted in great detail in the Atlantic Navies game from Clash of Arms, using the Command at Sea naval warfare system. Prospective Thai players are likely to do better in the game than their historical counterparts, as the game system doesn't account for differences in crew quality and players are likely to make a more energetic and coordinated approach than the actual event.