The pursuit of a united Europe has always been a political project. The treaties signed at Münster and Osnabrück in 1648, which put in place the Westphalian state system, sought to end the Thirty Years’ War within the Holy Roman Empire and the Eighty Years’ War between Spain and Holland. In 1815, the Congress of Vienna, following the Napoleonic Wars, specifically included defeated France in an intricate international architecture of which the Austrian and British foreign ministers were the principal designers. The subsequent Congress System kept the peace in Europe until the outbreak of the Great War in 1914. During that relatively irenic century, at the International Peace Congress in Paris in 1849, Victor Hugo appealed for a United States of Europe.
The Treaty of Versailles wrought vengeance upon the vanquished German empire, imposing a form of unbalanced peace which neither the League of Nations nor the 1920s conference system could save.