In 1848, the forces of reaction toppled as revolutionary movements spontaneously broke out all over Europe. While no single organization or doctrine united these movements, many made similar demands for constitutional governments, the fulfillment of nationalist aspirations, and the end to the restrictions of serfdom. However, the Revolutions of 1848 failed almost as rapidly as they won victories. While some governments made constitutional concessions, many resorted to military repression to stem the revolutionary tide. In France, the July Monarchy was overthrown and, temporarily, the Provisional Government sought to fulfill republican and radical ideals. Yet it was soon replaced by the authoritarianism of Napoleon III. The government of the Austrian empire collapsed under pressure from nationalists and republicans. However, the forces of counterrevolution soon reasserted themselves, and a new government sought to centralize the region. The Frankfurt Assembly failed to unify the German states, and liberal nationalism suffered another defeat. The Revolutions of 1848 brought a new toughness of mind to Europe, which showed itself in the philosophies of materialism, positivism, and realism. Among the disappointed revolutionaries of 1848 was Karl Marx, whose theories of dialectical materialism and historical development would soon earn both adherents and critics.