Murray Rothbard on the libertarian case against war

Let us assume for the moment, a world of two hypothetical countries: Graustark and Belgravia.  Each is ruled by its own State.  What happens if the government of Graustark invades the territory of Belgravia?  From the libertarian point of view two evils immediately occur.  First, the Graustark Army begins to slaughter innocent Belgravian civilians, persons who are not implicated in whatever crimes the Belgravian government might have committed.  War, then, is mass murder, and this massive invasion of the right to life, of self-ownership, of numbers of people is not only a crime but, for the libertarian, the ultimate crime.  Second, since all governments obtain their revenue from the thievery of coercive taxation, any mobilization and launching of troops inevitably involve an increase in tax-coercion in Graustark.  For both reasons - because inter-State wars inevitably involve both mass murder and an increase in tax-coercion, the libertarian opposes war.  Period.

~ Murray Rothbard, For a New Liberty, p. 332