The modern nation-state is one of the most significant and powerful of all human institutions. Many modern states have created constitutional systems and institutions that provide the justification for the exercise of power, a type of authority Max Weber called rational-legal authority. This liberal form of nationalism was dominant among nationalist political movements in the first half of the nineteenth century. In stressing the inherent uniqueness of people rather than universal human principles, romantic nationalism commonly highlighted the differences between nations and peoples. The process of German unification is a good example of how nationalism became a force of the political right in the second half of the nineteenth century. Racial and extreme nationalists celebrated war and conflict, arguing that the defeat of inferior peoples on the field of battle would cleanse the world of the weak. Members of European societies that had been shaken by economic change and political stability faced severe crises of identity.