Alexander Pope’s famous line, “Now Europe balanc’d, neither side prevails: For nothing’s left in either of the scales”, reminds us that peace without war is perhaps best achieved when there is a balance of power. Hugo Grotius’s concept of a just war was swallowed by the ambiguities of international law and the realpolitik of national self-interest. Special treaties of 1815 and 1839 guaranteed Switzerland and Belgium protection from attack but provided less protection for the latter. The Hague Convention III of 1907 established procedures requiring a formal declaration of war or an ultimatum before hostilities could begin. The Covenant of...