Libertarians oppose acts of aggression, acknowledging the core tenets of libertarianism, which state that individuals have a right to life, liberty and the pursuit of happiness.
While many libertarians espouse anti-war sentiments, they are not all absolute pacifists. The two main types of pacifism are absolute pacifism and conditional pacifism.
Absolute pacifism describes individuals who adhere to strict non-violence, even in self-defense. There is never a justification for violence.
Conditional pacifism states that non-violence should be practiced except in situations where more violence would occur if resistance is not implemented. An example would be if an intruder were about to kill your mother, father and two sisters. Killing the intruder to stop them from destroying your family would result in less violence.
Libertarians embrace non-violence but typically believe self-defense is the only justifiable case where physical force may be utilized. Most libertarians are conditional pacifists.
In the case of personal defense, most libertarians believe an equal or lesser action required to stop an imminent threat of violence is justifiable. That is, if a person is about to shoot you, then you are within your right to shoot them to stop the attack. Conversely, if they are only screaming and shoving you without the imminent threat of death, the use of deadly force is not administered.
In the case of war, most libertarians invoke conditional pacifism and call for a ceasefire until all peaceful means of resolving the conflict have been exhausted. Only in cases where it is absolutely necessary will libertarians endorse a defensive war strategy. That idea contrasts with the absolute pacifist who believes there is never a justification for retaliation or counter-strike.
The philosophy of libertarianism does not require adherents to be absolute pacifists. However, if a libertarian chooses to be an absolute pacifist, they are free to adhere to those principles.
For more information, see 'What is The Non-Aggression Principle?'
