Restructure society to value cooperatation over competition.

Break down unjustifiable hierarchies where possible and reasonable. The flatter the power structure is without sacrificing much in the way of efficiency, the better.

Create an Artificial General Intelligence with the sole purpose of satisfying people’s values through friendship and ponies.

Abolish Money and increase global distribution of goods aka socialism.

The complete extinction of the human race

When there’s no war, people like Hitler won’t have any opposition to their rise to power. Haiti never gains independence. We’d never have escaped feudalism.

Most wars are stupid bullshit and suck ass. The military, especially the US military, is the biggest waste of money ever. That doesn’t mean that war isn’t directly tied to lots of positive things like innovation. There’s so much medical, industrial, and geographical knowledge we wouldn’t have if it wasn’t for some war, and that’s just the tip of the iceberg. People’s ideas will always conflict because different groups of people are going to have goals unique to them that clash with others

Now if you were to ask how to stop unnecessary wars, better more efficient rulers. Most of the people in power today are complete hacks. It’s crazy

But I don’t think we’ll ever get rid of war and I don’t know if that’s necessarily that crazy? Ultimately it’s apart of how we grow as societies

Rename armed conflict to something like “special military operations”

Kill everyone. No people, no wars! Win/win in my book

Make everyone bulletproof and bombproof. If it is no longer possible to kill people using weapons of war, then there will no longer be a point to fighting the wars. Either that, or things will escalate to a point where it is no longer sustainable to fight wars that way, also solving it. Mind control, or gelatinising everyone into a singular hivemind is also an option.

Somewhat more realistically, I think that exchanges and the internet are the ways to go when it comes to ending wars. It’s a lot harder to fight wars when you can empathise with the other side, and see them as your peers. It’s one of the reasons why soldiers who took part in the Christmas Armistice were shuffled around, since they became friendly during the ceasefire, and would be less wanting to fire weapons on the friends that they made.

A lot of wars tend to centre around dehumnaising the other side, and treating them as the “enemy”. Allowing people to co-operate and communicate mutually makes it a lot harder for that to take place, since you have experience with the “enemy”, they’re not that bad. You’ve even got friends there, and training a gun on them with the expectation and desire to turn them into a corpse is just not on.

Mass extinction event. Breed out aggression from our species we seem to be doing that but slowly. Space mining could potentially stop us from having war in Earth at least. AI takeover have everyone live on their own virtual reality paradise. For the most reasonable I think the best way to end wars is education and uplifting poverty nations not exploit them.

Edit: Or we can just be like Switzerland be a direct democracy, with how slow they decide things it will be highly unlikely to go to war at all.

Let’s first address all the “nature” and “biological” not-really-true claims.

The Batek people of Malaysia are so averse of killing other humans that refuse to do it even when threatened with slavery https://peacefulsocieties.uncg.edu/societies/batek/

So, war is cultural, not biological.

Second, why do we do war?

At first glance, is for scarce resources, for survival.

But look at the modern wars. Are they for survival? Are they for resources that we need to survive?
No they are not.
They are for power.

But whose power?
The power of those who actually have to fight and die?
Certainly not.

The power of the rulers, who are greedy for more power.

Most people need to be scared into going to war, need to be convinced that they are defending their families and their “people”.

This is why rulers work very hard to build national identities, the good “us” vs the evil “them”.

Here we need three things:

1. We need a culture that knows how to recognize those greedy for power, those with a desire to dominate, and see them as the threat to freedom that they are, ie some sort of https://en.wikipedia.org/wiki/Leveling_mechanism
   There are several cultures that do that, but it has to be a deliberate and conscious thing.

2. We need to rethink our identities, national and not, because those identities are used to define the “other” that is ok to harm and kill.
   A way to do this is to make sure that people who want to travel and visit other groups can do so easily: this will help the various groups understand and humanize each other.

3. We need a culture that stresses the importance of non-violent conflict resolution.
   Because if all you know is violence, then that’s what you will use.

I mean, easier said than done of course, but I think that knowing the direction makes it easier to reach it.

For further reading on the subject, I would recommend Bob Altemeyer’s “The Authoritarians” and Graeber & Wengrow’s “The Dawn of Everything” from the top of my head.

There is this anime series called From the New World. The premise is a portion of humanity gained psychic power and led to the collapse of society because it’s so powerful that order could not be enforced. Far into the future there’s a cluster of community that’s able to exist, and the way they went about it was to genetically engineered humans so that they when they harm another human it triggers body functions that make it harder for them to breath and other things. Killing another human also kills the aggressor. It kind of works on the interpretative level so it’s possible that using drone could still have an effect, probably.

Education for everyone globally. War is, like all kinds of violence, an act or reaction of impotence (psychological term/not sexual).

It basically means nobody actually chooses to act violently or start wars. They do it because they believe consciously or subconsciously that they have no other options, because they can’t think of any options.

This is always a wrong assumption, because there is always a better option. The difficult part is to getting people to understand their actual options. Education solves this.

Kill all humans

This is something my old history teacher once mentioned: we have games like COD and other esports titles. Just have all conflicts resolved via virtual combat instead of in real world violence

Since you stipulated our species, to me, the answer is an external threat to the whole. Aliens, higher or lower dimensional creatures, cryptids, flame unicorns sharting lava, even angels or demons if we want to get real wild.

Even just the threat of an existential terror such as these and probably a lot I missed, (feel free to add to the list! Feed me your existential threats!) has the potential to bring the species together to fight on a larger scale.

However this doesn’t eliminate war just moves the focus. So I’m not sure if I’ve answered your question or not but I had fun doing it!