Murray Rothbard on how libertarians view war

Libertarians favor liberty as a natural human right, and advocate it not only for Americans but for all peoples.  In a purely libertarian world, therefore, there would be no “foreign policy” because there would be no States, no governments with a monopoly of coercion over particular territorial areas.  But since we live in a world of nation-states.  And since this system is hardly likely to disappear in the near future, what is the attitude of libertarians toward foreign policy in the current State-ridden world? 

Pending the dissolution of States, libertarians desire to limit, to whittle down, the area of governmental power in all directions and as much as possible… 

Specifically, the entire land area of the world is now parcelled out among various States, and each land area is ruled by a central government with monopoly of violence over that area.  In relations between States, then, the libertarian goal is to keep each of those States from extending their violence to other countries, so that each State’s tyranny is at least confined to its own bailiwick.  For the libertarian is interested in reducing as much as possible the area of State aggression against all private individuals.  The only way to do this, in international affairs, is for the people of each country to pressure their own State to confine its activities to the area it monopolizes and not to attack other States or aggress against their subjects.  In short, the objective of the libertarian is to confine any existing State to as small a degree of invasion of person and property as possible.  And this means the total avoidance of war.  The people under each State should pressure “their respective States not to attack one another, or, if a conflict should break out, to withdraw from it as quickly as physically possible.

~ Murray Rothbard, For a New Liberty, "War and Foreign Policy," pp. 331-332

1919 (published posthumously)