Perhaps, you did not realize it but most countries have signed a treaty to prohibit gas-air weapons on the battlefield. Yes, that is a fantastic way to explain it, and you certainly would not want to be on the losing end of this game. Incidentally the United States didn’t sign the treaty.
Why you ask, well, we’re the inventors of Napalm, and the more modern versions of gas-air weapons, that are even more deadly than previously, also more accurate, genuinely scary stuff, and whether the 1000-degree and fire will not kill you, all of the oxygen is pumped to the fire so that you suffocate, either way you don’t have any escape. Even countries refusing to sign the chemical weapons ban sign were worried about gas-air weapons in the skies.
Nowadays, we could easily send those deadly munitions from UAV (unmanned aerial vehicle) or drone. Again, scary things, but allow me to inform you of an even scarier potential invention for robotically dropped gas-air weapons using swarms of UAVs constantly refueling the weapon pods employing aerial refueling and unleashing this hell for hours and hours until there are no enemy infantry everywhere.
To begin with, I suggest having a pod of polymer balls that expand when filled to 2,000 times their initial size. They’ll be full of a liquid fuel-explosive mix, along with the polymer balls un-expanded will sit within the pod and after the gas enters the room”x-amount” of chunks will be discharged and like a membrane sponge soak up the gas until the inside cavity of the pod is stuffed. The liquid-fuel volatile will be moved into a reservoir at the UAV, the UAV will then search and strike within a swarm of 100s of different UAVs.
Once depleted of polymer balls and gas that the UAV will fly back up into the suitable elevation and match up with the airborne re-fueler and repeat as long as necessary, possibly days? Yes, I do have drawings, drawings and schematics and in case you’ve got a security clearance, then come look me up. Nobody wants or enjoys warfare, but if you end up in one, you have to acquire, and decisively. Please think about all this and consider it.