The trouble with realpolitik is when you get more cynical than reality itself. Instead of a binary---either the morality of chemical weapons caused their ban, or their uselessness in battle did---why not take a supply/demand, cost/benefit sort of approach? The moral repugnance of weapons of mass destruction makes them more costly to the users---if they delegitimize your war effort, what have you really gained? They c…
This is, in fact, explicitly stated in TFA. "This isn’t a value question, but a value-against-replacement question – why maintain, issue, store, and shoot expensive chemical munitions if cheap, easier to store, easier to manufacture high explosive munitions are both more obtainable and also better? When you add the geopolitical and morale impact on top of that – you sacrifice diplomatic capital using such weapons and…
Remote and automated warfare, coupled with more and more controlled/closed borders (we'll have these after COVID + economic crises) lowers the perceived cost and increases the benefits of using chem and bio weapons. Paradoxically, the better you'll be "prepared for a pandemic virus", the more in-control and confident you'll feel about indirectly using such weapons.
That's why we have to keep the world open and connected! And don't do the stupid thing of over-investing in surveillance and control that will only create dangerous illusions of being able to "safely" play with such "toys"!