Pacifism is the disavowing of all violence, even if it is used proportionally and in self-defense. This only works in cases where the power difference between parties is so huge that violence is not necessary for ending conflict (Ghandi's India for example). This is hardly ever the case.

If the goal is to limit the total amount of violence (and therefore self-inflicted suffering) a limited form of violence is still necessary to keep abusers of the social contract in check. But as individual and groups of countries have already shown, it is possible for human societies to be peaceful without war. The police may have to restrain individuals but wars are not necessary.