I think that war on a global scale, between nations-states can be stopped, that the only reason we haven't done so, is that currently, we can't handle the organizational complexity to do that. And the one thing reduces organizational complexity is technological progress.
If you look at long-term human behavior, I think a clear trend emerges: first, we competed with each other in tribes. Then, when agriculture was developed, we competed each other as small states. But the states had a lot of internal dynamics, a lot of different power centers competing each other.
In the last ~300 years, that internal competition has been reduced because of written constitutions, which couldn't be distributed widely without the printing press. The printing press also improved human literacy rates, which also has contributed towards peace.Then we had the telephone. I believe the UN, faulty as it may be, would not have survived for as long as it has, if humanity was as militant as it was 300 years ago.
I believe that the internet, and the phone, is the next step that will reduce organizational complexity even further.
Obviously, small scale violence will never stop, but i think large scale wars can, and will be stopped