Wars are just the final consequence from a scenario where people are already too damaged to talk to each other and to reach a consensus. It's an extreme decision, which only happens because people are facing extreme and chaotic scenarios. People who are in peace, happy with themselves and with the ones around won't have any desire to declare war or to fight against others. So, as we can see, people are highly unsatisfied with their own lives and with their relationships these days, despite all the technology and accessibility disponible to them.

And that is the kind of thing nobody can ban, because nobody has total control over someone else's free will. Treaties were signed, global organizations and alliances were created, leaders tried to sensitize each other, but in the end, it didn't work as anti-war mechanisms. Free will prevails, and if there is one man threating and instigating others, they will have to defend themselves. Otherwise slavery awaits...