You need to get a critical mass of people to despise war so much that they are ready to have disadvantages themselves to make a war free world a reality. E.g. complete stop of trade with countries starting a war or supporting such a country.
It happened before relatively successful with slavery and is partially happening with the death penalty. For me it seems like a very long way to go though.
In which case, any country willing to fund a military and start a war would dominate the world.
Slavery and the death penalty are poor analogies, and not just because slavery was stopped through quite a bit of violence, and the death penalty/imprisonment exists as an alternative to vigilante justice only by virtue of the state's monopoly on violence.
"If everyone just ..." is always silly, but it's especially silly when it comes to the belief that order can be enforced through anything other than -- ultimately -- the threat of violence. Everyone will not "just".
So, you're saying that this requires all people of the world get along and agree with anything that might cause war? That sounds like a reasonable plan! Thanks for the response.
That is not what I'm saying. There can be a lot of disagreement about a lot of things but there needs to be widespread agreement to not start wars and to use strong non-war mechanisms to stop war mongers. I know that it is far off from where we are today, but it is not impossible like needing everyone to agree with everything.
Can you expand on your solution to world peace?