If you take war to be violent conflicts between States, then anarcho-capitalists are ardently anti-war. Anarcho-capitalists do not see global politics with the conventional statist paradigm - as a collection of competing States, with every man on a State team. Anarcho-capitalist understand that rulers and subjects have very different interests. The rulers stand to gain power, prestige and popularity from war, whereas the subjects pay the costs, in lives and in money, and in standard of living and quality of life. Wars should be thought of as disputes between petulant power-maddened politicians. Thus rulers get the benefits of militarism, but shove the costs on others. They also seize upon war as an opportunity to ramp up power. Finally, they use the war as a propaganda tool to gain support for their rule.
Since the land area of the globe has been parcelled out among particular States, one of the basic doctrines of the State was to identify itself with the territory it governed. Since most men tend to love their homeland, the identification of that land and its people with the State was a means of making natural patriotism work to the State's advantage. If "Ruritania" was being attacked by "Walldavia," the first task of the State and its intellectuals was to convince the people of Ruritania that the attack was really upon them and not simply upon the ruling caste.
— Murray Rothbard, The Anatomy of the State
So far we've discussed traditional State on State wars. What about non-traditional wars, such as the "war" on terrorism? Anarcho-capitalists don't see the "war on terrorism" to be a bone fide war. Terrorism is criminal activity, and should be treated as such. It is justified to arrest the actual perpetrators of terrorism, but it is wrong to violate non-combatants. Terrorist acts should be handled as a criminal justice matter using peace officers, not as an inter-State war, with bombings and invasions and civilian casualties.
Most anarcho-capitalists believe that the modern State, by the very nature of way it fights wars, cannot possibly engage in a just war. Modern weaponry makes it impossible for a State to wage war without murdering innocent people. An obvious crime like the "9/11" attack is framed, not as a multiple homicide requiring police investigation, but as an act of war mandating military violence. And the flag-humping public bought it.