wat i dont understand who is using wat here
The Nazi , The Soviets or USA/UK or all together?
for the NAZI is clear, Hitler as victim of Gas Attack during World War One.
He strongly prohibited the use of Combat Gas on Battle field
the Allies wanted to use Combat Gas only in case the Third Reich used it.
IMHO no one to be willing to used Nerve gas in World war two
other wise it had left Europe and Japan depopulated !
Hitler changed his mind when the Soviet forces started to prevail over the Wehrmacht and push them back west toward Germany. He then ordered that poison gases, which may or may not have included early nerve gases, be used on the Russians.
However, his orders were creatively forgotten, lost, ignored, or otherwise defied by the entire chain of command.
From my reading on the subject, no one in any country's militaries was enthusiastic about gas warfare. Interestingly a lot of the most pessimistic evaluations came from officers who were experts in the field and therefore presumably had more of a vested interest than anyone in seeing them deployed.
The upshot of the escalation to gas warfare in WWI was that both sides invested both in more effective gas attacks and in more effective protective gear against the enemy's attacks, and with the latter being developed it all pretty much amounted to an annoying diversion of effort and funds from more conventional means of war that everyone preferred.
There were exceptions of course--the Japanese used poison gas in China and the Italians in Libya and Ethiopia. In both cases it was a matter of a first-rank (or anyway, second-rank!) industrial power waging war on third-world low-tech peoples who could not retaliate in kind.
All of this merely added to the horror people in general felt about this terrifying and therefore abhorrent mode of war; given that no one's forces wanted to be the first to use it against an enemy of comparable capabilities it was very easy for everyone to agree that gas warfare was a bad bad thing that no civilized nation should use. Even when Hitler firmly ordered its use, his establishment "lost" the orders because everyone agreed that there were more effective ways of employing the Reich's scant resources against the threat they faced and they couldn't afford such a foolish diversion.
To be sure--the reason gases were seen as a stupid waste of effort was that it was not that difficult to devise protective gear
for the troops; had there been an escalation of more massive attacks with more effective gases (and all through WWII only the Germans had the first versions of "nerve gas") probably the death and disablement toll on unprotected (or less well-protected) noncombatants would have mounted; doubtless Hitler was thinking of that and thinking "good!" in the case of fighting the Russians.
But even very effective gas weapons are of questionable advantage over a similar investment in more conventional artillery, bombs, guns, etc. Even for purposes of murdering enemy populations wholesale, there are more cost-effective approaches.