No Stupid Questions

You'll have to find a way to eliminate greed

Edit: or no people so you have nobody to start wars

A death match between the presidents / prime ministers of the rival countries. The country of the winner of that match will win the war, and the country of the loser has to deal with the following consequences.

There is no solution to that. It is a cold, hard reality of living on a planet with limited resources. We all might hate war (and for good reason, obviously), but it isn't like animals don't fight for territory either. Just happens that humans found a way to make it a few orders of magnitude more extreme.

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.

No hands for anyone. Possibly no feet too. Only the cooperative will survive.

How about massive free psychedelic doses?

Abolish Money and increase global distribution of goods aka socialism.

If you see war as a struggle to get access to scarce resources and if you notice that currently humankind is depleting most of the available resources then you might come to the conclusion that if in the future we will not need to go to war something terrible must have happened. Are you sure about the future you want?

Eradicate fear.

Fear of losing power. Fear of "them". Fear of going to hell because you didn't convert someone. Fear of lost resources.

It all boils down to fear. The problem is that fear is contagious. It's easier to convince someone to back your side if you make them afraid vs hopeful.

Kill every human, or all but one. As long as there’s at least two people, there will be conflict.

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

Put the ones in charge to the front line.

I think the solution is to have enough renewable energy for all of humanity.

this is a bit grim but global-wide information control that shreds any information which will help the growth of the idea of overly patriotic but less enough to not kill the domestic culture (but i think, not necessarily always telling the truth). that will also promote the sense of global village and transnationalism. and relocate the idea of war to other rivalries like on sports or something, idk.

basically limit the free will without showing it. I can't think if it's gonna happen or this even possible.

Well effectively, it would entail an all-encompassing global spying machine that gathers all data possible, and imprisons anyone who deviates from the expected baseline. (Wouldn’t end well for me either.) You have to remove most individuality to remove reasons for fighting. And even if you imprison 999 false leads to capture just one instigator, that’s the only way to ‘guarantee’ a fairly high level of security.

So what I’d say we need is 1984 or Мы levels of oversight to have any chance of curtailing conflict for good.

EDIT: oh, and re-education. Lots and lots of re-education.

Simple. We make war illegal.

Establish a global trade network in a way that everyone is completely dependent on everyone else.

It's (theoretically) impossible -- you can't break someone's (ignorant and established) will/ideas/plans with words alone or treats. Most world leaders are megalomaniacs by heart, i.e they won't stop until they are done with what they want.

Put everyone in a time-out until they can play nicely with the other children (because let's face it, a lot of them are acting like children)

Did you watch Shiny Happy People? Apparently Christian fundamentalists believe the world population can fit into Jacksonville, FL. There's the answer. Anyone who wants to start a war has to go live in Jacksonville. Build that wall!

Make tea

It would take way more but the first step it would be to remove religions. And not only because most are not peaceful in principle but also because some religions see others as a target. Even small difference in beliefs could spark a vicious and long standing conflic, like Catholics Vs protestants.