Libertarians believe in maintaining a strong national DEFENSE. I stress defense as we believe the US military is currently being utilized in an offensive manner. The US has a military presense in over 100 nations all over the world. We have been continually involved military campaigns since the early 1940's. We are currently operating a "war against terrorism" in Iraq. Each one of these points carries many discussion issues within themselves. My point is that as Libertarians we would look to bring our troop home from endless European, Middle Eastern and Asian conflicts. Conflicts that we should not be sending our young men and women to die in. Instead, redeploy them in the US in a truly defensive manner, as they were intended to be. Besides the greates benefit of saving the lives of US soldiers who would otherwise give thier lives fighting a "foriegn war". Just imagine the cost savings that would result. Don't forget war is costly business (200 billion in Iraq and counting). Libertarians would rather see individuals keep the money they earned to use as they see fit. Not to have it extracted from their pays (taxes) to help build a bridge, or blow up a building in some place they most likely never heard of.
Is your objection to war philosophic or utilitarian? If the latter, then I would would agree with you that most of the offensive wars that the U.S has fought in the recent past have been fruitless, unneccessary, and costly. However, this sort of policy in principle has often been both successful and required in the past, as it undoubtedly will again be in the future.
If the former is your cause for objection then, (1) I am shocked and (2) I must wholeheartedly disagree with you. In your qualm is morality/ethics, then perhaps you have not come to the realization that these things are meaningless in the world outside of yourself. You may hold yourself to a certain code of conduct based on your religion, or otherwise, but you have no concievable right to force those ideals on others or, by them , to manage a government. As a libertarian, you understand this already, I'm sure, considering the party views on issues like gay mairrage and abortion.
If your grounds are not moral, then what? I do not understand how you can agree in principle with the capitalistic practices of competion and yet negate the right of a nation to wage a war in self interest, a mere expression of free will, that one true inherant right of humanity.
In my mind, the zenith of human society would be an imperial republic, maintained by voluntary military service with the ideals of laizze faire libertarianism. I see nothing objectionable in this. Remember, a nation serves its people, rather than the contrary, but does not serve all of humanity. A government that does not consider the interests of its citizens above those of others, even if that means waging advantagous offensive war, is not doing its job.