The years from 1815 to 1848 provided a much-needed respite from the endless wars of the Napoleonic Era. From 1799 to 1815, Napoleon Bonaparte rampaged through Europe, conquering a vast empire and spreading the liberal ideas of the Enlightenment and laws based on them (the Napoleonic Code). When a coalition of European powers finally managed to defeat Napoleon for the last time, all the rulers wanted to do was return Europe "to normal". They didn't want Napoleon-style emperors marching their armies all over Europe, they didn't want legal equality among the classes, and they didn't want revolutions every few years. In short, they wanted stability, and the reorganization of Europe undertaken at the Congress of Vienna was aimed at creating that stability.
However, as much as the monarchs of Europe and their advisors wanted stability, there were several historical dynamics at the time that ensured that Europe could not "stay the same". In Great Britain, the enclosure movement of the early 18th century had created a large, socially mobile labor force, leading to the Industrial Revolution in British manufacturing during the 18th and 19th centuries. The years from 1815 to 1848 marked a period of particular industrial acceleration. While dramatically increasing the general power and wealth of England, the industrial revolution also particularly brought new wealth to the Bourgeoisie class of entrepreneurs and manufacturers. With their wealth came both influence and a desire for greater influence; the middle class demanded increased political representation and power. The middle class also developed a liberal ideology involving laissez faire economics, which they tried to make the dominant ideology in England. The battle between the once dominant aristocracy and the rising Bourgeoisie would open a floodgate of reforms, and this process would soon be replicated in the rest of Western Europe.
Also during this period, a young intellectual movement called Romanticism, which was a response to French Enlightenment Rationalism, held sway in Germany, Britain, and to an extent France. Romanticism challenged the ideal of universal standards for all mankind, and led to the glorification of the unique "national genius" of each ethnic and linguistic group. Thus, it was also during 1815 to 1848 that the modern phenomenon of nationalism was explicitly formulated. Tired of existing as a loose federation, many people in the fragmented German states hoped for German unification. The various Italian states sought Italian unification. Numerous groups within the ethnically diverse Austrian Empire dreamed of forming their own nation. The possibility of nationalists achieving their goals greatly frightened the reactionary rulers of Europe, who knew how destabilizing these changes might be.
Thus, the years from 1815 to 1848, though not plagued by rampant wars, can be seen as a more subtle battle between conflicting worldviews. On one side were the powerful and entrenched members of the Old Regime, who opposed change of any kind. On the other side were the forces of change: the bourgeoisie created by the dynamics of the Industrial Revolution, liberals, socialists, republicans, radicals, romantics, and nationalists. The struggle of ideas erupted in the form of various small-scale revolutions, first in 1830 and then on a more widespread scale in 1848, the year of revolutions. Although the revolutionaries were disappointed by results of 1848, ultimately change was on the way. And what would replace the old guard? The new systems, which are the "old regime" in our own time, owe a great deal to the then-revolutionary concepts developed in the era immediately following the Napoleonic Wars. The period from 1815 to 1848 was an important crucible in which were forged many modern ideologies, from classical "liberalism" (today's conservatism) to communism. In some respects, the result of this battle between ideologies that reached fever pitch in the early 19th century is still being resolved today.