About the year 1870 Europe entered upon a new phase in its history with the final achievement of the nation-state in Germany and Italy. The emergence of two nation-states in central Europe marked the sole great change within the European system of states during the century between the Congress of Vienna and the first World War. It was a change that transformed the system without disrupting it. Two predominant features of the nineteenth century, liberal constitutionalism and the principle of nationality, characterised this event; the third dynamic of the age, socialism, did not make its advent till the revolt of the Commune in 1871.

In the 1870's liberalism was at the zenith of its historical course. In most of the countries of Europe it had brought into existence written constitutions with parliaments, a widening franchise, and constitutional guarantees of personal freedom. The last relics of legal inequality and bondage were removed by the Revolution of 1848 and Russia's abolition of serfdom in 1861. Equality before the law and personal freedom had practically everywhere become principles in law, despite strong opposition from both the feudal aristocracy and the bourgeoisie. Liberalism had thus achieved its civil programme; but the liberals' constitutional aims, an executive controlled by parliament and a legislature with unlimited powers, had been realised only partially and in differing degrees in the various countries. From about the mid-1870's the liberal parties, hitherto drawn from notabilities in the middle classes, became more and more involved in difficulties that raised problems of form and organisation.