For millennia, people have armed and prepared their nations for battle. The results have been disastrous, with an almost constant flow of wars that have left vast numbers of people dead, crippled, blinded, or traumatized, with their nations often in ruins. In this context, during the twentieth century nations did manage to establish international institutions that, it was hoped, could safeguard national security through the development and enforcement of international law. Unfortunately, however, after so many years devoted to conflict and war, it has been difficult to get nations to relate to one another in this new way. Even so, given the existence of these international institutions for only a tiny portion of human history, it would be premature to abandon efforts to create an effective international security system. And there are practical measures that can be taken along these lines.