War is horrible, and all lovers of God abhor it. However, as much as I hate war, I love justice, and sometimes justice calls us to raise our hands against the unjust. Loving peace is one thing, being willing to allow injustice to thrive based on your "ideals" is another. I think a lot of people claim the title "pacifist" to hide their own cowardice to act in the face of true evil. There's nothing wrong with talking and negotiating, but evil cannot and should not be compromised with.
This doesn't even call in the question of "duty and obligation" to one's country and homeland, which is for another thread entirely.