A dose of Mises,

From here:

When a peace-loving nation is attacked by a bellicose enemy, it must offer resistance and do everything to ward off the onslaught. Heroic deeds performed in such a war by those fighting for their freedom and their lives are entirely praiseworthy, and one rightly extols the manliness and courage of such fighters. Here daring, intrepidity, and contempt for death are praiseworthy because they are in the service of a good end. But people have made the mistake of representing these soldierly virtues as absolute virtues, as qualities good in and for themselves, without consideration of the end they serve. Whoever holds this opinion must, to be consistent, likewise acknowledge as noble virtues the daring, intrepidity, and contempt for death of the robber. In fact, however, there is nothing good or bad in and of itself. Human actions become good or bad only through the end that they serve and the consequences they entail. Even Leonidas would not be worthy of the esteem in which we hold him if he had fallen, not as the defender of his homeland, but as the leader of an invading army intent on robbing a peaceful people of its freedom and possessions.

How harmful war is to the development of human civilization becomes clearly apparent once one understands the advantages derived from the division of labor. The division of labor turns the self-sufficient individual into the dependent on his fellow men, the social animal of which Aristotle spoke. Hostilities between one animal and another, or between one savage and another, in no way alter the economic basis of their existence. The matter is quite different when a quarrel that has to be decided by an appeal to arms breaks out among the members of a community in which labor is divided. In such a society each individual has a specialized function; no one is any longer in a position to live independently, because all have need of one another's aid and support. Self-sufficient farmers, who produce on their own farms everything that they and their families need, can make war on one another. But when a village divides into factions, with the smith on one side and the shoemaker on the other, one faction will have to suffer from want of shoes, and the other from want of tools and weapons. Civil war destroys the division of labor inasmuch as it compels each group to content itself with the labor of its own adherents.

Mises is using the term "liberal" in its original sense. If you go to this link, he explains what that means.