What if Japan invaded & occupied Thailand in September 1941?

But they were allies?

USA, Britain and Dutch? informally I'd say from a "lets deal with Japan" perspective.

Japan and Thailand? more complicated.

Put yourself in Phibun's shoes. You can resist a Japanese invasion, you lose and are subjugated, with no real prospect of any Allied (Britain and USA) help, or you do a deal, give up bases, and accept a lot of Japanese influence on decision making. Pragmatically you do the deal to survive. As a comparison look at Finland, who had to give, who was far better equipped to resist.

Only when things went very badly for the Allies did Thailand become active militarily and form an alliance with Japan
 
USA, Britain and Dutch? informally I'd say from a "lets deal with Japan" perspective.

Japan and Thailand? more complicated.

Put yourself in Phibun's shoes. You can resist a Japanese invasion, you lose and are subjugated, with no real prospect of any Allied (Britain and USA) help, or you do a deal, give up bases, and accept a lot of Japanese influence on decision making. Pragmatically you do the deal to survive. As a comparison look at Finland, who had to give, who was far better equipped to resist.

Only when things went very badly for the Allies did Thailand become active militarily and form an alliance with Japan

It's an interesting question as to how Phibun and the Thai military would have responded if Japan had not been able to offer the face saving prospect of giving them a share of the conquests. If it is just Thailand being invaded I would have thought it would have gone over quite poorly?
 
Don't forget that from 1942 on while officially allied with Japan, the Thai government was still divided into pro-japanese and pro-allied camps. Pridi Bamonyong, who refused to sign the declaration of war on the United States formed the Free Thai Movement which grew to over 90000 strong and engaged in intelligence gathering, sabotage, and rescuing allied airmen.

Also on a side note, the Thai government was so divided that the Thai ambassador to the USA refused to deliver the declaration of war, which in return caused the United States not to DoW on Thailand. The situation there was... complex, to say the least!
 
The UK does not have extra assets to reinforce anywhere in the far-East. At least not without weakening another front. I think the US is iffy to up the defensive capability of their Pacific bases.

The absolute 1st thing Japan has to do is end the conflict in China while they are fighting the allies. (I know this is the "dog chasing his tail" discussion, but the only way Japan has a chance to win is by releasing the assets they need from the China theater)

If Japan can neutralize the China war they can release 15 to 30 divisions for other operations. That will give them the numbers to overwhelm the Dutch and British in the DEI and Burma.

The real issue Japan will have is their logistics network is (will be) quickly overwhelmed. Japan doesn't have enough shipping to allow for an effective logistics network for their expanded empire.
 

raharris1973

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Japan declaring war on Thailand might end up being a lot like Napoleon deposing the King of Spain. Changing a tepid ally into a bloody quagmire.

IMHO- this is way overestimating the power of karma over power-political affairs. And, the Japanese won't be demanding any kind of regime change, even of Phibun, unless he drags things out in the Japanese view. Even then, the Japanese won't threaten the monarchy.
 
If Japan can neutralize the China war they can release 15 to 30 divisions for other operations. That will give them the numbers to overwhelm the Dutch and British in the DEI and Burma.

The real issue Japan will have is their logistics network is (will be) quickly overwhelmed. Japan doesn't have enough shipping to allow for an effective logistics network for their expanded empire.

I think the second para is the one that hits the Japanese harder. Even if they did have the 15-30 divs available, they couldn't deploy them all as invasion forces. It would take them a year, Id guess, to deploy with sufficient supplies stockpiled.

The pass the US gave them was the whole torpedo fiasco, imagine the lost of tankers so much earlier in the war.

Conversely, the Japanese didn't try a parachute drop on the Borneo oilfields, which, surely were the ones to try a "Coup De Main" on. Capturing these quickly, intact could have been a help. Could be a nice little ATL here!
 

raharris1973

Gone Fishin'
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It's an interesting question as to how Phibun and the Thai military would have responded if Japan had not been able to offer the face saving prospect of giving them a share of the conquests.

Well, Japan had already helped them gain some Cambodian and Laotian territory at French expense, through its friendly mediation.

Now if the Japanese are moving to occupy Thailand without simultaneous attacking the British, then yes, they cannot immediately or openly promise the Thai territory from Burma or Malaya to help Phibun save face at that moment.

On the other hand, the Japanese could try to sweeten the deal for the Thai by offering them even *more* of Laos and Cambodia in return for alliance and military basing rights.

Don't forget that from 1942 on while officially allied with Japan, the Thai government was still divided into pro-japanese and pro-allied camps. Pridi Bamonyong, who refused to sign the declaration of war on the United States formed the Free Thai Movement which grew to over 90000 strong and engaged in intelligence gathering, sabotage, and rescuing allied airmen.

Also on a side note, the Thai government was so divided that the Thai ambassador to the USA refused to deliver the declaration of war, which in return caused the United States not to DoW on Thailand. The situation there was... complex, to say the least!

All true and a good point.

However, this just seems like a wise move by a small, weak power. Keep a foot in both camps (like the Scottish clans sending a son to fight on both sides of a rebellion so one will always be on the winning side and able to advocate for the family, from Master of the Ballantrae). From where the Thai Ambassador sat, the U.S., his decision made total sense, America's power and long-term advantages were right in front of him. For Phibun in Bangkok he is looking at a lot of Japanese right in front of him with Americans nowhere to be seen on the ground. Sure, the Free Thai movement emerged and grew. But its growth tracked tio a great extent the turning of the tide in the war, especially in Burma.
 
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