No Stupid Questions

There is no such thing as a weapon that is only capable of being used for defense. It’s a logical contradiction on the order of a true paradox such as “this statement is false”. It is theoretically possible to have some sort of defensive shield with no way to move it, but even such a thing could be deployed offensively as an area denial tactic, ask any rts player. If you can stop force, it can be used as force.

Another way to think about it is the old question of which would win, the proverbial unstoppable force, or the immovable object? Einstein’s theory of relativity gave us a framework to say that both terms refer to exactly the same thing. An immovable object, by definition, is actually an unstoppable force. And an unstoppable force, by definition, is an unmovable object.

So it goes with weapons. A weapon is a weapon by its nature. It is only the wielder who decides if it is defensive or not. If you can’t trust the wielder, then you can’t trust the wielder, and that’s basically it, and the root of all problems.

Often times defense weapons cause more alarm with neighboring countries. If you can't attack or harm them then theoretically they can strike you at will and remain safe. They can act like trump and if it does not work out they can pull out after being a dick and not worry about it. Its kinda the horror of war and its consequence which drives peace. That being said it is battrump. This is why subs are a big deal as it means you could attack and completely win on a country and they could strike back.

Part of war is occupation of territory and a what cost. So defensive structures to hinder army's movement making it more costly for taking on occupaing it. Bogs are a natural defense are costly in money and time to remove. A courites weath and Ally's is also a good deturent. All of these can be used offensively but are the least treating. If a war is to costly any dictator wil look weak and be at risk of loosing power. Final thought protection of human rights world wide helps to stop war spreading and the cases of war like poverty.

The distinction between defensive and offensive weaponry is a bit of political theater. Like the first boots on the ground in Vietnam were "military advisors." Sure, a missile shield is more defensive in nature but its rockets or drones would not refuse to go on the offensive, if so ordered, on philosophical grounds. A rifle may aid in repelling an attack as well as participate in it. So the premise of your strategy is on shaky ground.

If something is purely defensive and incapable of harming anyone else then it's not really a "weapon" at all. It would be more like... I don't know... A really big shield?

It's a nice thought on paper but I don't think a big shield being put up is going to convince any other country to stop producing more weapons.

It may actually lead to them producing more powerful weapons if they think they need to get past a big-ass shield now

Look at the Swiss. They have set up tank barriers and heavily fortified artillery all over the country. The Swiss Alps are basically one big fortress. All across the place you can find buildings looking like houses at first sight, but which turn out to be heavily armored artillery positions, especially at landscape gaps near the border. You can't cross with tanks because of several rows of concrete teeth hiding in the vegetation, and the only road passing through runs through at least three or four targeting areas.

If everyone was defensive only then there wouldn't be a need for a defense. It's a core principle of military combat that a good defense is offense, can't shoot back if their already dead.

"Defence only" gives an attacking side 100% initiative and control over what's going on. They can focus on one place, attack when you are the weakest, take control of that one place (city, village or even a building) and even if it costs them a lot, you have no way to punish it. They can take their time to recover and wait and attack again whenever they want.

you can use any weapon offensively if you are creative enough, even minefield

I mean there's the Iron Dome the US helped fund for Isreal. It's a short range air defense system. It's not built for offense, and wouldn't work well for it from what I understand.

But even that there's still the 'self-defense' mentality where the iron dome could shoot down non-combatants flying within range because of a supposed threat.

Nuclear landmines?

Some sort of energy-absorbing energy shield or force field? Doesn’t exist yet.

Even in Star Trek, anything with a shield has some sort of weapons too.

Well we haven't blown ourselves up (so far) from the fear of mutually assured destruction. It seems to have worked for north Korea as well.

"An atom-blaster is a good weapon, but it can point both ways." — Salvor Hardin, The Merchant Princes (Isaac Asimov, 1944)

I would say no.