The Battle of Koh Chang, 14th January 1941

By David Manley

Despite the fall of France in 1940 the Vichy government still held sway over France's colonial territories abroad. One of these territories was French Indo-China, what we know today as Vietnam and Kampuchea (Cambodia). With the defeat of mainland France obvious doubt was thrown over her ability to defend the far flung outposts of the empire. French Indo-China held a particular attraction to her neighbour to the West, Thailand. In late 1940 the Thais began a series of cross border attacks by troops and aircraft against the French possessions, aimed at annexing those parts of French Indo China which the French were unable to hold on to. These attacks tended to concentrate in the coastal regions of Cambodia, to the west of Saigon. The Thais naturally saw themselves as filling a power vacuum which had been created by deflating French colonial interests. The French, however, had other ideas and a state of war was assumed between Vichy France and Thailand (then still often referred to as Siam). Since the main thrust of the Thai assaults had been along the coast the French considered a naval operation against the invaders, although there was grave concern over strengths of the Thai armed forces which would oppose such a mission.

The Royal Thai Navy could in no way be regarded as a pushover. A number of new vessels had recently been delivered from Japan and Italy. The major units of the fleet are listed in Table 1, and included two Japanese-built armoured coast defence vessels which displaced 2,500 tons and carried 8" guns, two older British built armoured gunboats with 6" guns, twelve torpedo boats and four submarines. In addition the Royal Thai Air Force had in its inventory over 140 aircraft, including relatively modem Mitsubishi Ki-30 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 may be mounted. Other less capable aircraft in the Thai inventory included 25 Curtiss Hawk 75N, 70 Vought Corsair biplanes, 9 B-10 bombers and several Avro 504 trainers.

Despite the strengths of the Thai forces the French Governor General of Indo-China and Commander-in-Chief Naval Forces, Admiral Jean Decoux, decided that the naval mission should go ahead. A small squadron, the Groupe Occasionnel, was formed on 9th December 1940 at Cam Ranh Bay, near Saigon, under the command of Captain de Vaisseau Berenger. The squadron consisted of the light cruiser Lamotte-Picquet, the colonial sloops Dumont d'Urville and Amiral Charner, and the older sloops Tahure and Marne. There was no air cover to speak of, apart from eight Loire 130 seaplanes based at Ream which provided reconnaissance. Additional scouting was provided by three coastal survey craft, and intelligence gleaned from the local fishermen.

Berenger's squadron began training manoeuvres in Cam Ranh Bay shortly after coming together. Early in the new year, on January 13th 1941, Admiral Decoux formally requested Berenger to send the squadron against the Thais to act in support of a land offensive planned for the 16th. This operation was intended to throw back Thai forces which had been advancing along the coast. Because of the disparate speeds of the French ships Berenger sent the slower sloops on ahead, whilst he remained in Saigon to complete the final elements of the plan. Several options were currently being prepared, the Admiralty in Paris having recently given its formal blessing to the use of naval forces in support of the army. The final planning meeting of the 13th saw an immediate delay in the execution of the operation for 24 hours. With the plans finalised, Berenger sailed in Lamotte-Picquet, the delay in the start of the operation allowing him to refuel at Cap St. Jacques before the rendezvous with the slower ships at 16:00 on the 15th, 20 miles North of Poulo Condore.

The orders from Admiral Decoux were clear and simple, "Seek out and destroy the Siamese naval forces from Satahib to 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 knots, the best speed of the sloops. The French ships remained undetected as they entered the Gulf of Siam, but their quarry was not so lucky. The Loire 130s from Ream had completed a sweep of the coast from Krat to Satahib. They had located one coast defence ship and three torpedo boats at Koh Chang, and one gunboat, four torpedo boats and two submarines at Satahib. Their report was sent to Marine Headquarters in Saigon, who retransmitted the report to the Lamotte-Picquet. Berenger considered his options in the light of this intelligence and opted for a dawn attack on Koh Chang. He discounted an attack on Satahib because it was not possible for the sloops to reach the port until later in the day, by which time the Thai force was likely to have been alerted to the French presence and the element of surprise would be lost. In addition there was doubt as to the contribution which the harbour defences at Satahib could make. Finally the force at Koh Chang, although formidable, was the weaker of the two and was thought to offer the best chance for victory.

Berenger's plan of attack was as follows. The squadron would approach at dawn from the South West. Because the anchorage at Koh Chang was surrounded by islands and islets, many of which were over 200 metres high, the squadron would break up and use the cover of the islands to concentrate fire on portions of the Thai squadron whilst covering all the avenues of escape. The easternmost channel was regarded as the most likely route by which a breakout would be made - this was the most suitable route and was also the area in which the recce report had placed the largest Thai ships. The Lamotte-Picquet would head to the eastern side of the anchorage to block this route whilst the colonial sloops blocked the centre and pounded the Thai ships there. The smaller French ships would concentrate to the West.

 

The Attack

The French squadron closed on the anchorage at 05:30 on the 17th. At 05:45 they split into the three groups as planned, the Lamotte-Picquet heading for the Eastern part of the anchorage, Dumont d'Urville and Amiral Charner continuing to the central position and the 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 coastal defence ships. This came as a nasty surprise to the French - previous reports led them to believe that only one of the large defence ships was present, but during the night the Dhonburi had arrived to relieve the Sri Ayuthia, which was to return to Satahib later that day. Once their presence had been passed to the Lamotte-Picquet the aircraft attempted an attack of its own using bombs, but was forced off by a heavy barrage of AA fire. The effect of this mission was double edged - the French were now aware that they faced both the Thai heavy units, but the element of surprise had been wasted and there was still thirty minutes to go until sunrise. Caught napping by the oncoming French the Thais desperately began to raise steam and make preparations for slipping their anchors. The coastal defence ships had an advantage over their smaller consorts since, being diesel powered they were able to get under way almost immediately.

Despite their initial shock at coming under attack it was the Thai forces which opened fire first at 06:14 when the range had come down to 9,000 metres. The French responded almost immediately. Lamotte-Picquet fired at the dark shapes in the anchorage and fired a spread of three torpedoes at 06 20. One torpedo was seen to hit the coastal defence ship Sri Ayuthia. Heavily damaged by the torpedo and gunfire she headed for the cover of the islands and was finally beached on the mainland. The torpedo boat Trad then became the Lamotte-Picquet's next target. She was heavily damaged and also disappeared behind the cover of the islands, where she later sank. Fire then switched to the remaining torpedo boats, Chonburi and Songhkli, which were rapidly overwhelmed and abandoned. Gunfire from the sloops finished them off at 07:00.

At 06:38 the lookouts on the Lamotte-Picquet spotted the second coastal defence ship, the Dhonburi, at a range of 10,000 meters heading to the North West. 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 inaccurate. By 07:15 fires could be seen on the Dhonburi, which then found herself engaged not only by the cruiser but also by the sloops. Believing they had a better chance of hurting the smaller French ships the Thais shifted their fire onto the Amiral Charner, which soon found 8" salvoes falling around her. The Dhonburi shifted fire back to Lamotte-Picquet after a salvo from the French cruiser put her after turret out of action. Soon she reached the safety of shallow water which the French ships could not enter for fear of grounding, but it all came too late for the hapless Thais as the Dhonburi was burning fiercely and listing heavily to starboard. At 07:50 the Lamotte-Picquet fired a final salvo of torpedoes at a range of 15,000 metres but lost sight of the Dhonburi behind an island from which she was not seen to emerge.

For the next hour the French ships patrolled the area, picking up survivors and ensuring their victory was total. At 08:40 Berenger ordered the squadron to head for home, but this coincided with the start of the expected Thai air attacks. Several bombs were dropped close to the Lamotte-Picquet but a vigorous barrage was put up by the ship's AA guns and further attacks were not pressed home. The final raid departed at 09:40, following which the victorious French squadron returned to Saigon.

The French left behind them a scene of total devastation. The Sri Ayuthia was heavily damaged and hard aground on a sand bar in the mouth of the Chantaboun river. She was later raised and repaired by the Japanese, survived the war, but was sunk by Thai shore batteries on 3rd July 1951 during an attempted revolution. The Thai transport Chang arrived at Koh Chang shortly after the French departed and took the Dhonburi in tow but she eventually capsized that afternoon and was a total loss. The torpedo boats Trad, Chonburi and Songhkli had all been sunk. The only survivors were the torpedo boat Rayong, the minelayer Nhong Sarhai and the fishery protection vessel Thiew Uthok. These three ships, which had been sheltering to the North of Koh Chang, wisely chose not to break cover and thus were not observed by the French. At a stroke the cream of the Royal Thai Navy (stand fast the four submarines) had been wiped out. The French were elated, for they had inflicted a defeat as decisive in its way as the Japanese at Tsushima. 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 accept). In the end though it was all for nought - five days later the Japanese government offered to 'arbitrate' in the search for a peaceful settlement, and soon confirmed the Thai annexations. Even this state of affairs did not last for long, as Thailand was invaded later that year during the attacks on Malaya, and was forced to return her short-lived gains to France at the end of WW2.

Today the island of Koh Chang and its surrounding waters have been designated a Maritime Nature Reserve. Nothing remains visible above the surface to remind the visitor of this remarkable battle.

 

Wargaming Koh Chang

This relatively small action makes for a classic naval wargame, rich with 'what if' possibilities and is also eminently suitable for a mini campaign. For those interested in the latter I have included a map showing the coastline between Saigon and Bangkok, noting the various bases and anchorages (click here to download - 242k). Since this is a relatively small action I would suggest a set which goes into some detail, as the capabilities of the smaller ships are more likely to be better represented. Those with unlimited funds and time will probably find that the best way to do it is to use 1/1200 models in the largest area possible and use a set of rules such as 'Command at Sea'. Those with more modest tastes will find that a less complex set of rules, such as the Skytrex WW2 set, or 'War At Sea' are better suited and more financially acceptable. These rules use standard warship data as their starting point and data cards for the ships can be easily created from tables 1 and 2 below. Another alternative is to use the ever-popular 'General Quarters'. This goes into less detail and begins to show its limitations when many small craft are involved, but has the advantage of being a 'fast play' system and which, if used with 1/3000 miniatures, allows a battle of the size of Koh Chang to be fought on a normal sized wargames table in an afternoon. Because of the popularity of 'General Quarters' I have included details of the ships involved in the Koh Chang battle as they would be represented in those rules (see Table 3). 'General Quarters' also has the advantage of a ready made campaign system, so the campaign map accompanying this article is drawn to a scale of 15 miles per hex to match up with the scales in the rules.

The main problem with war gaming this action is the relative lack of models. As far as 1/3000 scale is concerned I believe the only ship involved for which a model is available is the Lamotte-Picquet with examples provided by Skytrex and Navwar. However, SDD are known to be working on a range of Thai warships in this scale, and these will soon be available. Moving up in scale to 1/1200 the French cruiser again is available. I do not have details of the availability of the other ships, but experience suggests that if a warship was built this century then at least one 1/1200 manufacturer has covered it!

Scenario Specifics

If fought as a one-off battle there are a number of possibilities that could be explored as well as fighting the battle 'straight up'. I offer the following suggestions and considerations which players may wish to expand on:

a) Variable Thai forces - listings are given for all the major fleet units of the Thai navy. Naval wigwams should be used to aerial intelligence giving inaccurate reports, so the exact composition of the Thai force at Koh Chang could vary considerably. For a randomly generated force, roll a d10

Die Roll
Effect

1
Only a single coastal defence ship is present

2
Replace the coastal defence ships with the armoured gunboats

3
Add one of the armoured gunboats to the force

4
Add both the armoured gunboats to the force

5
Add a submarine to the force

6 - 10
No change to the Thai forces

 

b) Another variable is the arrival of the Thai air force, which could have made a great impact (literally) on the outcome of the battle. I would suggest the following random arrival of the first wave, again rolling a d10:

Die Roll Effect
1 First raid arrives at 07 30
2 First raid arrives at 07:45
3 First raid arrives at 08:00
4 First raid arrives at 08:15
6,5 First raid arrives at 08:30
7-10 First raid arrives at 08:45

Thereafter, roll a d6 at the start of each turn (six minutes for 'General Quarters'). On a roll of 6 a flight of three Ki-30s arrives over the table. Each flight has an endurance over the table of three turns, allowing a limited opportunity for the Thai player to co-ordinate their attacks.

For those without data on the Ki-30 it was a twin seat light bomber, similar in concept to the Fairey Battle. It had top speed 260mph, a maximum altitude 28,000 feet, and was armed with one or two fixed forward firing 7.7mm machine guns, and one aft firing 7.7mm MG in the rear cockpit. It was capable of carrying three 220-pound bombs or their equivalent.

The Thai pilots, whilst well trained in ground attack techniques, were less well equipped to attack ships. They should be penalised when bombing anything other than a stationary target. In 'General Quarters' terms apply a +1 modifier to the Bomber Hit Table. The 'General Quarters' do not consider bombs of less than 5001b to simulate the attacks of the Ki-30 adjust 2 columns to the right on the Bomb Damage Table. Remember also that the Ki-30 is not capable of dive bombing missions.

c) Terrain is an obvious feature of this action. Obviously if a ship ends a turn with its target behind one of the islets its line of sight will be blocked and no firing will be possible. Temporary blocking behind the islets should also be considered. If the target is observed at the end of a turn, but was obscured behind an islet for part of the turn a negative modifier should be applied to the chance of hitting. In 'General Quarters' terms a -1 modifier is applied to the Straddle Table.

d) Visibility played an important part as the action was fought at dawn. Initial visibility was in the order of 10,000 metres at the start, rising to normal daylight visibility about one hour after sunrise. In 'General Quarters' terms this equates to 40 inches at the start of the 06:30 turn, rising to 120 inches by the 07:30 turn (increasing at 8" per 6 minute turn).

e) Gunfire from the Thai coastal defence ships was heavy but erratic. A negative modifier should be applied to the shooting of the 8" guns, again in 'General Quarters' terms expressed as a -1 modifier.

f) The Thais were caught at anchor. The French reports refer to the Thais as 'raising steam', a process which could take several hours, but it is extremely unlikely that the boilers of the Thai ships would have been completely cold, especially since several units were expecting to sail that day. In any case, steam pressure was required for the turbo alternators which provided electrical power, so steam pressure would certainly be available. Roll a d6 for each Thai steam powered vessel at the start of each turn after the approach of the French forces has been detected. A 5 or 6 means they have sufficient steam pressure to make headway and can get under way that turn. Those ships with diesel engines (as noted in Table 1) can get under way immediately the alarm is given.

g) Prior to the French collapse in Europe the heavy cruiser Suffren had also formed part of the Indo China Force, but she had been recalled in early 1940 and was interned at Alexandria. A plausible "what if?" variation to the scenario could investigate the effect of retaining this ship out East. In this case the Suffren could be added to the force, or could replace the Lamotte-Picquet. Adding the heavy cruiser to the force is likely to unbalance the scenario and should only really be used if the Thai player is more experienced than the French. A more appropriate use for this variant is the mini campaign where the addition of the Suffren is likely to encourage the French player to act more aggressively.

h) The French also had two Redoutable class submarines stationed in Indo-China, one of which was the Pegase. Although they played no part in the Koh Chang action they could also be added to the French order of battle for the mini campaign. The French could have called on support from five river gunboats although they were fully employed in patrolling the rivers of South East Asia and would have been of questionable value.

 

References

The following references were consulted in the writing of this article:

C W Koburger, ‘The Cyrano Fleet’, pub. Paeger, New York, 1989.

David Brown, ‘Warship Losses of World War 2’ Arms ands Armour, London 1995

C Shores, ‘Bloody Shambles, Vol. 1’, pub. Grub Street, London 1992

Conways ‘All The World’s Fighting Ships, 1922-1946’, pub. Conways, London 1980, 1987

J. Guiglini (trans. K Macpherson) ‘A resume of the Battle of Koh Chang’ Warship International 1990 No.2

 

Table 1 Thai Navy, January 1941.

Name, Type

Displacement

(tons)

Speed

(knots)
Armament Armour, notes etc.
RATANAKOSINDRA SUKHOTHAI

1000

12

2x 6"

4x 3"AA

2.5" belt, barbettes and turrets,4.5" conning tower, 1.5" decks.

British built armoured gunboats

SRI AYUTHIA

DHONBURI

2265

15.5

4x 8"

4x 3"AA

4x 40mm AA

2.5" belt, 4" barbettes, conning tower and turrets, 1.5" decks.

Japanese built coast defence ships

PUKET, CHANDARUBI

CHONBURI, CHUNPHORN,

PATANI, RAYONG,

SONGHKLI, TRAD

SURASDRA,

470

31

3x 3"HA

2x 20mm 6x 21" Torps

Torpedoes in 2 twin and 2 single mounts Italian built torpedo boats
TACHIN, MEKLONG

2000

17

4x 4.7"

2x 20mm

4x 18" Torps

Japanese built sloops, used as training vessels

KANTAN

KYLONGYAI,

TAKHAI

135

19

1x 3"HA

2x 20mm

2x 18" Torps

Japanese built torpedo boats
BANGRACHAN NHONG SARHAI

408

13

2x 3" HA

2x 20mm

142 mines

Italian built minelayers

Diesel powered

SINSAMUDAR

BLAJUNBOL

MACHANU, VILUN

430

14.5

8

5x 21" Torps

1x AA HMG

Japanese built coastal submarines

4 bow, 1 stern tube

Speeds are surfaced and submerged

CMB 6-9

16

40

2x 18" Torps

2x AA MG

2x DC

British built 55' coastal Motor Boats (CMB) of WW1 design.

SARASINDHU,

THIEW UTHOK,

TRAVANE VARI

50

9
1x 37mm Fishery protection vessels

 

Notes to Tables 1 and 2:

1) Those vessels present at Koh Chang are listed in Column 1 in BOLD italic type

2) Guns listed as HA are High Angle

3) A complete listing has been presented for 'what if' scenarios.

 

Table 2 - French Colonial Forces in Indo China, 1940-41

Name, Type

Displacement

(tons)

Speed

(knots)
Armament Armour, notes etc.
LAMOTTE-PICQUET

9350

33

8x 6.1"

4x 3" AA

4x 13.2m AA

12x 21" Torps

Dougay Trouin Class cruiser Carried two Loire 130 seaplanes, but catapult damaged and was unable to operate them. Sunk by US Aircraft 12/1/45
AMIRAL CHARNER DUMONT D'URVILLE

2600

15.5

3x 5.5"

4x 37mm

AA 6 AA MG

50 mines

Bougainville class sloops. Maximum speeds were 18.5 knots, but fouling and engine problems limited them to 15.5 knots.
TAHURE

850

20

2x 5.4"

1x 75mm AA

4xAAMG

20 DC

Amiens Class sloop
MARNE

601

21

4x 100mm

lx 75mm AA

Marne Class sloop. Marne scuttled 10/3/45 at Can Tho
SUFFREN

9938

31

8x 8"

8x 3"HA

12x 13.2mm

12x 12" Torps

Carried 2 Loire 130 seaplanes.

Rebuilt after the war and was finally scrapped in 1974.

ARGUS

VIGILANTE

218

12

2x 3"

2x 37mm

River gunboat
FRANCIS GARNIER

639

12

2x 3.9"

1x 3"

2x 37mm

River gunboat

MYTHO

TOURANE

95

10
1x 47mm River gunboat

 

 

Table 3 - Major Warship Data in 'General Quarters' Format

Name

M/S

DF

AA

Armament Boxes

Hull Boxes
Lamotte-Picquet

6"/3"

3CL

1

6/1(6)

4/1(6)

3/½ (3)

2/-(3)

12

9

6

3

-
Dumont d'Urville

5.5

2CL

1

2

2

1

1

7

5

3

2

-
Amiral Charner

5.5"

2CL

1

2

2

1

1

7

5

3

2

-
Tahure

5.4"

2

1

1

1

1

-

8

6

4

2

-
Marne

3.9"

1

1

2

2

1

1

8

6

4

2

-
Suffren

8"/3"

4CL

3

9/3(6)

7/2(6)

4/2(3)

2/1(3)

12

9

6

3

-
Sukhothai

6"/3"

2DD

1

2

2

1

1

5

4

3

2

-
Sri Ayuthia

8"/3"

2CL

1

4/1

3/1

2/-

1/-

7

5

3

2

-
Dhonburi

8"/3"

2CL

1

4/1

3/1

2/-

1/-

7

5

3

2

-
Rayong

3"

1DD

1

1(6)

1(4)

½ (2)

½ (1)

13

9

6

3

-
Songhkli

3"

1DD

1

1(6)

1(4)

½ (2)

½ (1)

13

9

6

3

-
Chonburi

3"

1DD

1

1(6)

1(4)

½ (2)

½ (1)

13

9

6

3

-
Trad

3"

1DD

1

1(6)

1(4)

½ (2)

½ (1)

13

9

6

3

-
Nhong Sarhai

3"

1DD

1

1

½

½

-

5

4

3

2

-
Thiew Uthok

-

½ AA

½

-

-

-

-

4

3

2

1

-
Tachin

4.7"

1DD

1

1(4)

1(4)

½ (4)

½ (-)

6

4

3

2

-

Notes

M/S Main/secondary armament

DF Defence Factor (including armour type)

AA Anti Aircraft factor


Naval/Home