Every war in history was started by government; one, or more. How to Stop Wars
Therefore to end war, you have to end government.
They start wars regardless of Party. So far in America Democrat presidents have started more wars, and so killed many more Americans in uniform, than Republican ones; but the latter seem eager to catch up. So to end war, you have to end government. All of it.
Yes, of course that's radical. Wars - and governments - have been going on for ten thousand years. Nothing less than radical action is going to change that. Repeat: to end war, you have to end government.
Powerful as they seem, governments do rely upon support. Therefore, to end governments, withdraw support.
Above all, they need people to work for them. So, to end governments you must refuse to work for them. That's it. Denying them employees - people, like you - is not hard. Just decline to work for them, and persuade everyone you know to do the same. Here are some tools to help:
The QuitGov site quickly shows every visitor why it's morally wrong to work for government. Short URL: TinyURL.com/QuitGov
The Anarchist Alternative site (takes about an hour) explains how society will work nicely without government
The Freedom Academy site provides a greater-depth education, to change minds permanently. Take the course, and having graduated bring to it one friend a year to do the same. And naturally, leave any government job you hold.
When nobody will work for government, it will cease to exist. And when it ceases to exist, there can be no more wars.
It's not hard, it's 100% peaceful and non-violent, and it takes less than a single generation. So just do it.