That great British historian A.J.P. Taylor once pointed out that the history of Europe in the post-Napoleonic 19th century divided very neatly into three periods, each three decades in length.
The system established at the Congress of Vienna 1n 1815 endured till 1848. During this time the continent was dominated by intensely conservative forces, and there were no major wars between the Great Powers.
1848 was the Year of Revolutions. In state after state, governments lost control of their capital cities to the crowds on the streets, and fled. There was intense excitement and turmoil for a while, but then in almost every case the revolutions failed after a few months and the old regimes were restored. (The words "socialism" and "communism" first came into common use around this time) However, there was no peace internationally, because the next thirty years witnessed a whole sequence of wars involving almost all the nations of Europe. The Crimean War was followed by the Franco-Austrian War in northern Italy, followed by the Austro-Prussian War and the Franco-Prussian War, and then in the later 1870s the Russo-Turkish War in the Balkans. In the midst of all this, Garibaldi's campaigns produced a unified Italian state for the first time since the days of ancient Rome, and Bismarck welded together the petty German states into a new German Empire which rapidly supplanted France as the military and economic powerhouse of Europe. New states were also created in the ever-troublesome Balkans: Serbia, Romania and Bulgaria; poverty-stricken little states, suspicious of each other and always likely to be used as pawns in the rivalry between the Russian and Austrian Empires. Possibly coincidentally, the period also saw two exceptionally bloody conflicts outside Europe: the Indian Mutiny and the American Civil War.
The decades of violent conflict came to and end with the Congress of Berlin in 1878, which established a status quo in Europe that endured for a generation. For the next 30 years there were no wars in Europe, leaving the Great Powers free to expand their overseas empires. Africa was carved up between the European states during this period, with even new countries like Germany and Italy contriving to muscle in on the deal. The penetration of China went on apace, the French established themselves in Vietnam and the Russians were able to complete their conquest of Central Asia.
Thirty years brings us neatly to 1908, when the Austrian occupation of Bosnia provoked a new wave of Austro-Russian hostility and rivalry in the Balkans. The final collapse of Turkish control over the region led to small but brutal wars between the young Balkan states. The unstable personality and unpredictable behaviour of the Kaiser William II led to Britain abandoning its foreign policy of "splendid isolation" and allying with France and Russia against Germany, and the stage was all set for the cataclysm of 1914.
So Taylor points to three contrasting periods. His interpretation seems to be supported by the Marxist historian Eric Hobsbawm in his massive three-volume history of the century. Hobsbawm entitled his volume covering 1875-1914 "The Age of Empire", and his volume 1848-1875 "The Age of Capital"; though this book could equally well have been "The Age of Conflict". Similarly, Norman Stone entitles his volume of the 'Fontana History of Europe' as "Europe Transformed: 1878-1919", and James Joll's international history begins in 1870. All these books tactitly recognise a major transformation beginning in the 1870s.
Why history should have followed this rhythm has been hotly disputed. Taylor was always opposed to any broad ideological interpretations, and once said that, although one could argue that capitalism was the underlying cause of the coming of war in 1914, then surely capitalism was equally the cause of the generation of peace after 1878. Certainly the 19th century witnessed unprecedented economic and social changes. Industrialisation, and particularly its most spectacular aspect, the building of the railway networks, was under way before 1848 and proceeded at great pace in all the states of Europe in the middle period. The years after 1878 were marked by the "Great Depression", another phenomenon much debated by historians. Society was transformed utterly in the most advanced states, like Britain, after 1848: for the first time in human history, more people lived in towns than in the countryside. After 1878 living standards rose, and states began directly intervening in the economy, providing universal education and the first attempts at social security. In almost every European state there were moves towards democratically-elected Parliaments. Spectator sports made their sudden appearance, culminating in the first modern Olympic Games. Political philosophy also reflected the rhythms: Karl Marx, for instance, born in 1818, formulated his ideas in the first of our three periods, did almost all his writings in the second period, and died in 1883. By 1900, with Marx's expectations of revolution looking nowhere likely to come true in the immediate future, his followers were locked in hot debate as to the continued relevance of his ideas in the light of subsequent social and economic developments; the "revisionism" of Bernstein being violently opposed by the continued hard-line revolutionary commitment of Lenin. In retrospect, both could have been held to be either right, or wrong!