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The Arab Spring is generally discussed in terms of the prospects for democracy. Equally significant is the increasing appeal — most recently in Syria — of outside intervention to bring about regime change, overturning prevalent notions of international order. The modern concept of world order arose in 1648 from the Treaty of Westphalia, which ended the Thirty Years’ War. In that conflict, competing dynasties sent armies across political borders to impose their conflicting religious norms. This 17th-century version of regime change killed perhaps a third of the population of Central Europe.