Between the wars, it was a commonplace that poison gas would be used in the next war, would be used in large quantities, and would probably be used against civilians. This was a natural enough assumption; after all, it was used liberally enough in the Great War, and it was widely assumed that science would have discovered even more lethal gases.1 As for civilians, they were now in the front line, as the Zeppelins and Gothas had shown.
Of course, gas wasn't used in the Second World War,2 probably because of the fear of retaliation in kind, i.e., deterrence worked. This could not be assumed a priori, of course, particularly since it was in fact in use throughout the period 1919-39. The best known, and the most egregious, example was by the Italians in Abyssinia (modern Ethiopia), in 1935-6. There were other instances too, but I don't think I've ever seen a comprehensive list (though this isn't bad).
So the other day, I dug out an old issue of Strategy and Tactics (July/August 1980).3 S&T is a wargaming and military history magazine, which has a complete wargame in every issue. But it also has well-written articles (or at least did, haven't bought an issue in many years), and in this particular issue I think the line "honestly, I only read it for the articles" is true, as the game in this issue was the much-maligned Tito, on a subject I don't recall having much interest in. And the articles in this issue include one on chemical war: "Chemical warfare: perspectives and potentials", by Austin Ray. Of interest here is a table on alleged uses of gas after the First World War. The source for the data is given as Stockholm International Peace Research Institute, The Problem of Chemical and Biological Warfare, volumes 1 and 2 (New York: Humanities Press). So, here's the section up to 1939:
|1919||UK vs. Red Army||Archangel||Tactical||Sternutator||M-device||?|
|1920||Red Army vs. White Russians||Kakhovka||?||?||Gas cylinder||?|
|1920?||Red Army vs. ?||Turkestan||?||?||Aircraft||?|
|1920-5||UK vs. rebels||Mid-East||?||?||Aircraft||?|
|1925||France vs. Morocco||Fez||Terror||Mustard||Bombs||?|
|Early 1930s||Govt. of Manchuria vs. insurgents||Manchuria||?||?||?||?|
|1930s||USSR vs. Basmatch tribes||Central Asia||Tactical, terror||Mustard||Aircraft spray||?|
|1935-6||Italy vs. Ethiopia||Ethiopia||Tactical, terror||Various||Air spray, bomb||15000 total|
|1936||Spanish Government vs. Fascists||Guadarrama front||Tactical||Tear||Artillery||?|
|July 1937||Japan vs. China||Yangtze front||?||Mustard||?||19|
|August 1938||Japan vs. China||Juichang||Tactical||?||?||600+ fatalities|
|July 1938||Japan vs. China||Chou Wou||Tactical||DC||Candles||?|
|September 1938||China vs. Japan||Ch'ing Hua Chen||?||Phosgene||Captured Japanese artillery||?|
A few comments and corrections are in order. A sternutator is a sneezing agent, i.e. just a harrassing or irritant gas. I'm not sure what an 'M-device' is -- I'm guessing something along the lines of a Livens protector or Stokes mortar. DC is methylphosphonic dichloride, which seems like an odd inclusion -- it seems that it is not a weapon in its own right, but a precursor chemical to various nerve gases. But I don't think Japan had nerve agents at this time -- only Germany did. So why Japan would be messing about with DC is unclear, unless it actually can be used as a weapon, or it means something else here. (It could even be a typo. The second-last entry in the table is out of chronological order -- it's not clear if the date is wrong or if the rows have just been mixed up or what.) And I'm not sure what a 'candle' is, in this context -- the name suggests burning something. In Abyssinia, Italy employed tear gas, mustard and phosgene.
The claimed British use of gas against 'rebels' in the Middle East (specifically Iraq) is hard to get a straight answer on. It was certainly advocated by Churchill (then War and Air Minister) but whether it was actually carried out is unclear. But if it did happen, it would have been perfectly consistent with French and Spanish use of gas against the Rif tribes in North Africa (and note that Spain is missing from the above table). The S&T article itself notes that the Red Army attack on White Russian forces was only planned, and not executed, but is included to represent many claims of 'Red Army chemical warfare preparations' (whatever that means). Another note says that China alleged more than 889 uses of poison gas by Japan; these are much more credible than similar claims during the Spanish Civil War (the one listed in the table is apparently reasonably firm, and that's only tear gas).
The other interesting point is that, other than Abyssinia, virtually all these uses of gas were for the most part ignored in the West, even while it was in other ways continually harping on the aero-chemical threat to civilisation. Maybe it was a combination of factors which led to Ethiopia being singled out: it combined a large scale of use, a relative closeness to Europe, and the involvement of an agressive, expansionist power -- none of the other cases had this trifecta. But the upshot is that these other gas attacks might as well not have happened as far as the military intellectuals were concerned.
This is leaving aside the argument of those like the chemist J. B. S. Haldane, that the statistics showed that gas warfare led to relatively fewer fatalities than shells and bullets, and so was therefore more humane than conventional war, as well as the argument that all likely gases useful for warfare had already been discovered. The German discovery of nerve gases, had this been publicly known, would have put the lie to these claims. ↩
There are some dubious claims to the contrary, such as that Germany used gas against Soviet troops in the Crimea in 1942. ↩
I hasten to add that I'm old, but not THAT old! I bought it long after it came out. ↩