We can think of libertarianism as falling between two poles: the anarcho-libertarian that views all government as a threat and the classical-liberal that views government as necessary but inherently dangerous.
Both poles worship the free market but each side approaches the origin of the free market from different directions. This difference in concepts of the origin of the free market creates many of the divides in libertarian thought. For example, it predicts whether a libertarian will or will not support a war.
(Note: Iím simplifying for reasons of clarity and brevity. These are poles on a theoretical spectrum, not either/or binary states.)
What a free market is free of is violence. Individuals make economic decisions based on the advantage it brings them not out of fear of being hurt or killed by another human. We usually think of the violence as arising from the implicit threat of violence lying behind all government laws but a free market can also be destroyed by individual-to-individual violence on many different scales. Once people begin making economic decisions based on fears of violence from any source, the free market begins to die.
The anarcho pole views the free market as a natural phenomenon that existed prior to government and could exist independent of any government. Humans donít have to carry out any conscious action to create a free market. The free market exists until a human takes a deliberate action to destroy it through an act of actual or threatened violence.
The classical liberal views the free market as an unnatural phenomenon. The classical liberal thinks that violence and intimidation are fundamental facets of human existence. The free market only comes into existence when violence is removed from human interactions by conscious intent. The free market exists in an artificial and unstable bubble of non-violence created by a minimal but effective State. Outside the bubble violence is always seeking to rush back in and destroy the free market. The government that forms the bubble is itself violence and can grow out of control and also destroy the free market. The bubble is maintained by counteracting natural violence with government violence. It is always a precarious balancing act.
These two models of the origins of the free market generate different views on the utility of war.
Anarcho view warfare as counterproductive. War is an exercise in violence that attacks the natural free market regardless of by whom or why the war gets fought. If governments stopped acting, the natural free market would eventually assert itself.
Classical liberals view some wars as necessary either to protect the free-market bubble or to expand it. Sometimes, if the government does not act, the free-market bubble will be destroyed by violence.
In the War on Terror, Anarcho generally oppose it and classical liberals generally support it. Anarcho believe internal security precautions and external warfare are cures worse than the disease. Classical liberals believe that the precautions and warfare are necessary to protect the bubble. Both views are logically consistent with their axiomatic beliefs about the origins of the free market.