You might be one of those libertarians, or you belong to some other creed, who think war can be eliminated. For example through international trade, the better use of our ratio, or more influence for regular people on foreign policy decisions. In my own work I have tried to make clear all of these claims are false, and many related ones as well. This is all in the writings of Hume, Smith, Hayek or Rand. The base line is that in human nature reason cannot overcome the emotions, at least, not with all people, at all times. This means that conflict is one of the perpetual characteristics of human action, both in domestic and international settings.
In the unlikely case you do not want to take my word for it, read this book. Coker is a professor of International Relations at the London School of Economics and Political Science, specializing in the study of war. In this short but powerful book, he clearly sets out the different reasons why war will not be eliminated, providing evolutionary, cultural, technological, geopolitical and a number of other reasons. Buy it, and your world view and view of human nature will be even more aligned to the great classical liberals.