Did the Japanese plan to meet a US invasion of Japan with poison gas?

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Steve
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Did the Japanese plan to meet a US invasion of Japan with poison gas?

Post by Steve » 11 Aug 2021 16:21

What follows is taken from a recent program on Japanese NHK Television titled “Poisonous Secrets”. The program makers not only looked at Japanese chemical weapons but also at American planning to drop chemical weapons on Japan. Japanese professor Yoshimi Yoshaki from Chuo University said that if the US had used poison gas the Japanese military was willing to retaliate in kind. I thought this opinion (which is what it seemed to be) was not borne out by what the program showed.

China was used as a proving ground for Japanese chemical weapons with large scale use of them. The program talked to a 98 year old man who had been assigned to unit 526 of the Kwangtung Army. He said his unit undertook secret training in preparation for a war against the USSR. Professor Yoshaki said that “The Japanese Imperial Army anticipated war with the USSR. When that happened they wanted to use a poison gas blitz”. Unit 526 exercised with the infamous unit 731 using live people euphemistically called logs.

Japans largest poison gas plant was on Okunoshima Island in Hiroshima prefecture and a man who had worked there for three years was interviewed. The plant manufactured 6,600 tons of mainly mustard gas. At the end of the war the Americans found 3,000 tons of mustard gas there and the commentary said “that the Japanese military had not had time to hide”. If one assumes that there had been time to hide a large amount then a very large amount of mustard gas was stockpiled at Okunoshima.

After air raids on Japan started the Japanese Army Scientific Research Institute pushed ahead with development of chemical weapons. The Institute was divided into 9 groups and dispersed around Japan. One production site was at the city of Takaoka and a man who worked there was interviewed. According to the commentary “he said that they were developing chemical weapons to use in the event of a US military invasion”. The Institute worked on numerous new weapons (documents were shown) including mass dispersal systems and gas spraying tanks. A suicide weapon was devised consisting of a portable gas cylinder fitted with an atomiser. After the Emperor’s surrender speech a “huge” amount of cyanide solution was dumped into the sea and the workers were told to keep quiet.

In 1944 the Japanese Navy started large scale production of poison gas at Sagami Naval Arsenal with 3,000 people working on its production. A man who was sixteen when sent to work there was interviewed and drawings were shown of the production line. A munition named Number 6 Mark 1 was made packed with 17 kg of mustard gas and designed to be dropped from an aircraft.The Navy positioned 43,000 of these munitions around Japan. In 2002 11 people were injured at the site of the arsenal when over 800 beer bottles filled with mustard gas were discovered.

From June 1945 boys as young as 15 were being mobilised and the program talked to a boy mobilised at 17. He was trained to throw special grenades nicknamed “Shorty” at tanks. The grenades were made of glass and contained cyanide gas which was meant to kill the tank crew.

A “dispersal site” for the army’s poison gas was at the seaside town of Yugawara and a man who had worked on its disposal at the age of 16 was intervened. The day after the war ended disposal of poison gas started but all the higher ranks left for Tokyo and the work was left for the lower ranks. After dark containers of mustard gas were taken a long way out to sea and dumped.

A US intelligence report on Japanese chemical Warfare said that the army had stockpiled 3,647 tons of poison gas and the navy 326 tons at 20 sites for a total of 3,973 tons. This is very likely wrong as adding up just the amount found at Okunoshima and the amount in 43,000 navy munitions gives you 3,719 tons. That the Japanese only managed to dump 254 tons before work stopped is difficult to believe.

It cannot be said for certain but I would say that on the balance of probabilities a US invasion of Japan would quite likly have been countered by a “poison gas blitz” which is how apparently they were going to use it against the Soviets.

With the end of the war Japan’s military leaders needed to get their story straight on what had gone on. A manual was produced titled “Unifying Our Views About Poison Gas” which gave guidance on how to reply during interrogation to avoid culpability for crimes. The manual was shown on the program though it had burn after reading written on it. They were to say that the use of poison gas was never ordered or authorised by Imperial Headquarters. Chemical weapons charges against Japans military leaders were not brought to trial which must have been a great relief for them.

EwenS
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Re: Did the Japanese plan to meet a US invasion of Japan with poison gas?

Post by EwenS » 11 Aug 2021 23:15

The 1925 Geneva Protocol banned the use of chemical and biological weapons. But it did not ban their development and production. All the major powers, both Allied and Axis, produced chemical weapons in WW2 and carried them around and stored them in rear areas of the battlefield just in case the other side used them first. The Allies never used them, but were quite prepared to do so if for, example Germany, used them first. For example:-
https://en.m.wikipedia.org/wiki/Air_raid_on_Bari

As far as their use against Japan is concerned certain senior officers, like Gen Marshall, would have had no qualms about using them. Immediately before Potsdam Marshall received confirmation from MacArthur that CW training was being stepped up and supplies of CK (cyanogen chloride), mustard, tear gas and phosgene were being brought forward from Australia to Luzon. By mid Aug “adequate stocks” were on hand.

There were also plans to destroy Japanese crops with chemical and/or biological weapons. These were shelved about May 1945 when it was realised that feeding the population in captured areas would add to the strain on US logistics.

When interviewed postwar by US intelligence personnel, the staff of the Japanese Second General Army stated they did not envisage actively using chemical weapons because they knew the the US chemical reaction would overwhelm them. But they believed that if the US faced defeat in the Kyushu landings the US was likely to use them. They believed the Japanese army to be well equipped against US chemical weapons but the civilian population had no protection.

Now that might be playing the issue down but if attacked chemically then I’ve no doubt the Japanese would have reacted in kind given the prevailing world view at the time. As far as prosecutions are concerned, at the time the evidence of their use in China was IIRC, not conclusive, or at least widely known. As noted merely possessing them was not illegal. Added to that the US had an interest in protecting certain figures involved in Japanese chemical and biological weapons programmes in order to exploit their experimental findings. See the foot of this article:-
https://en.m.wikipedia.org/wiki/Unit_731

So the US had an interest in not making too much of an issue of it immediately postwar.

And don’t forget Britain also developed, produced and stored not only chemical but also biological weapons and Churchill would happily have used them against Germany but was restrained by the Chiefs of Staff. Those with experience of WW1 in France were reluctant to see their use in WW2 and that seems to have been the only restraint.

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Steve
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Re: Did the Japanese plan to meet a US invasion of Japan with poison gas?

Post by Steve » 12 Aug 2021 13:34

Hello, I have now found where the NHK program can be seen
https://www3.nhk.or.jp/nhkworld/en/onde ... o/3016083/

America in 1945 seemingly considered attacking Japan with gas as a way of limiting troop losses before any use by the Japanese. The US Chemical Warfare Service suggested air raids using poison gas bombs targeting 25 cities. Before an amphibious assault 1,000 bombers would rain mustard gas on Japan causing perhaps 5 million casualties. According to the program training in Japan for poison gas warfare was well under way and the program shows large numbers of people with gas masks.

Interviews conducted after the war with senior Japanese commanders over poison gas are I would suggest of dubious value. They would be likely to say only as much as they thought was needed and would try to put a gloss on what they did say. We now know (maybe before?) that documents were prepared on how they should respond to questions about poison gas and to ensure they all sang from the same hymn sheet. Would the Japanese have been prepared to see Kyushu overrun when they had poison gas?

In May 1946 at the Tokyo war crimes trials there was an indictment for the use of poison gas in China. Prosecutors had evidence from a top secret Japanese army document listing 56 examples of the use of poison gas. The US Chemical Warfare Service had the charges dropped.

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