It may be a stupid question...but why doesn't a country simply use something like "LSD gas" or "psyilocybin gas"? The assumptions are: 1) it renders people temporarily crazy and docile / compliant, 2) it will wear off in a day or two, 3) people will fully recover, 4) while they are gassed, you can just gently shepherd them out of their dwellings / fortifications and onto buses to take to refugee camps or something, while they have an out-of-body mystical experience and comprehend the totality of existence.
Everybody wins.
It seems that a non-lethal / no permanent disability hallucinogenic agent would not violate the treaty against chemical/biological weapons, would basically achieve passive area denial, with create zero casualties, and would (if it actually worked as intended) probably be a heck of a lot of fun (ignoring all the un-fun aspects of war like "these new people now own this territory and here are the consequences for everyone who used to own it".)
Note: if a gas is impractical as delivery mechanism (hello, gas masks), be creative: a 'contact agent' (skin absorption ~~ like DMSO), cheap 'cluster darts' sprayed from drones, etc, etc.
Everybody wins.
It seems that a non-lethal / no permanent disability hallucinogenic agent would not violate the treaty against chemical/biological weapons, would basically achieve passive area denial, with create zero casualties, and would (if it actually worked as intended) probably be a heck of a lot of fun (ignoring all the un-fun aspects of war like "these new people now own this territory and here are the consequences for everyone who used to own it".)
Note: if a gas is impractical as delivery mechanism (hello, gas masks), be creative: a 'contact agent' (skin absorption ~~ like DMSO), cheap 'cluster darts' sprayed from drones, etc, etc.