The invaluable Anthony Gregory has an excellent piece on the libertarian case against war. He both argues from first principles and makes the consequentialist case that war is destructive of ordered liberty in any society. Here's an excerpt:
"The moral principles of individual liberty that are so obviously compromised by the vociferous taxing, regulating and mass killing of the warfare state are complemented by libertarian economic and practical arguments against war. Not only is war a violation of the rights of the individual – which we must always oppose on moral grounds – but on balance, it has failed to produce security, much less peace and liberty, for most people it has touched."
Murray Rothbard used to argue that the American Revolution was the exception to the rule that war and revolution almost always lead to less liberty. There may be other exceptions, but my knowledge of history, while more extensive than that of your average bear, is not voluminous enough to come up with one. For the more extensive case, check out Robert Higgs' classic: "Crisis and Leviathan."