> Or imagine a lethal compound

You'll get nuked (or similar WMD) for that.

Imagine a somewhat more realistic set of applications for hot new research chemicals.

How about aircraft or shells or covert actors spray some "thing" that shorts out electrical insulators 1000x more often than normal. Or makes the vegetation underneath power lines 1000x more flammable than normal vegetation. Our power is unreliable causing a major economic hit both directly and via higher electrical bills. If "they" want to invade now the civilians won't have power and be more likely to get out of the way long before the front line troops arrive. I mean you could probably put nano-particles of graphite in a spray can right now, then stand upwind of a power station or substation, but I bet extensive research would do better. A lot of high power electrical "Stuff" relies on plain old varnish being inert for a long time ... what happens if it wasn't? Again you shut down a country they gonna nuke you, but what if electrical power transformers and switching power supplies only last one year on average instead of ten? Thats a huge economic and maybe military strategic advantage but would you get nuked back because some nation's TVs burn out in one year instead of the carefully value engineered ten years?

How about a spray or microbe or whatever that screws up air filters. Who cares, right? Well most troops (and cops) in most countries have gas masks. Zap their masks via whatever new magical method, then drop simple plain old tear gas the next day or until logistics catches up, which will take awhile assuming they even know they're damaged. Normally when hit with CS, they'd mask up and the CS would have no effect on mask wearers other than reduced vision, but now the side that didn't get their masks ruined has a HUGE tactical advantage.

If you make a bioweapon and kill half the population, they gonna be PISSED and you're gonna get nuked. So try something a little more chill. If your vitamin A reserves are gone, your night vision is temporarily essentially gone. Yeah for long term vit A deficiency you'll get long term skin, general growth, and infection risk problems, but if someone sprayed you with some weird compound that made you pee out all your bodies stores of Vit A before tomorrow morning, the only real short term effect would be night blindness, and that would go away in a couple days with a normal-ish diet or by taking a few days of multivitamin pill or a couple supplement vit A pills. So spray the enemy (and/or the civilians) and they can't see in the dark so magical automatic curfew for the civvies and attack the night blind military and absolutely pound them because they're night blind and can't see your guys. If they have NVGs then hit them at dawn/dusk when the NVGs won't work completely correctly but they can't see without them because of night blindness. Its temporary and never hurt no one other than the opfor "owning the night" until the victims figure it out or naturally recover, so at a strategic / diplomatic level would a country nuke another country because they couldn't see at night for a couple days? Naw probably not. And you can imagine the terror attack / psych warfare potential of leaflets explaining, "we turned off your night vision for a couple days, now obey or we shut off cardiac function next time" Either for the government to use against civilians (think Canada vs truckers) or governments to use against each other (China vs Taiwan invasion or similar). Or give them temporary weird fever sweats or turn their pee robins-egg blue or all kinds of fun.

Now the above is all sci fi stuff I made up and AFAIK I'm not violating any secrets act, unless this post magically disappears in a couple hours LOL.

Think of the new non-lethal battlespace like computer virus attacks. Yeah, we could "EMP" Russia to shut off most of their computers and they'd be really pissed off and nuke us right back so thats a non-starter. But release "windoze annoyance virus number 31597902733" and that could have real world effects. Especially if you release 20,30,4000 new zero-days on the same day.