Martin Feldstein (1997):
EMU and International Conflict: For many Europeans, reaching back to Jean Monnet and his contemporaries immediately after World War II, a political union of European nations is conceived of as a way of reducing the risk of another intra-European war among the individual nation-states. But the attempt to manage a monetary union and the subsequent development of a political union are more likely to have the opposite effect. Instead of increasing intra-European harmony and global peace, the shift to EMU and the political integration that would follow it would be more likely to lead to increased conflicts within Europe….
What are the reasons for such conflicts? In the beginning there would be important disagreements among the EMU member countries about the goals and methods of monetary policy. These would be exacerbated whenever the business cycle raised unemployment in a particular country or group of countries. These economic disagreements could contribute to a more general distrust among the European nations. As the political union developed, new conflicts would reflect incompatible expectations about the sharing of power and substantive disagreements over domestic and international policies….
Although 50 years of European peace since the end of World War II may augur well for the future, it must be remembered that there were also more than 50 years of peace between the Congress of Vienna and the Franco-Prussian War. Moreover, contrary to the hopes and assumptions of Monnet and other advocates of European integration, the devastating American Civil War shows that a formal political union is no guarantee against an intra-European war. Although it is impossible to know for certain whether these conflicts would lead to war, it is too real a possibility to ignore in weighing the potential effects of EMU and the European political integration that would follow.