As the 18th century changed to the 19th century, the big question in Europe was this: what would the French Revolution lead to? Europe's rulers had good reason to be concerned. The social leveling reforms in France had led to the destruction of aristocratic privilege and the execution of a king. If these reforms spread to other countries, the conservative regimes then in power would suffer. And as France made these reforms, such as opening positions of leadership to all men based on talent, the country became more efficient, powerful, and increasingly patriotic. As people at all levels of French society began to feel more of a stake in France's future, the power of the masses was starting to be tapped unlike ever before in history. Napoleon, a minor Corsican aristocrat who rose to be Emperor of France, represented the new confidence in social mobility and individual talent the Revolution had wrought. And although he was a dictator, Napoleon was in many ways very progressive, advancing many of the goals of the Revolution, and rationalizing government and social processes wherever he went. Napoleon represented change.
Nearly all of Europe fell under Napoleon's control, and certainly all of it was forever changed by being ruled by him or fighting against him. Napoleon came closer than anyone else in modern history to conquering Europe. The war he provoked can be thought of as an early kind of "world war". Napoleon's wars echoed in the New World as well, influencing the War of 1812 and Toussaint l'Ouverture's dictatorship in Haiti.
Even as it spread conflict, Napoleon's conquests spread the new ideas and new institutions of the French Revolution throughout Europe. The countries he occupied had versions of the Napoleonic Code imposed on them, forming the legal basis for much of Continental European law today. The liberal ideals of legal equality codified in his law system spread to his opponents to, as reformers like Baron Stein and Hardenberg realized that to compete with France, they had to create a Prussian state that was like France. Thus, Napoleon spread the ideas of the French Revolution even beyond the boundaries of his vast empire.
Napoleon's regime also helped mobilize nationalist movements. In reacting to their French overlords, some previously disunited linguistic-ethnic groups saw reason to organize. In opposing France, these groups built up nationalist movements, most notably in Germany. Germany even reacted intellectually, starting to champion Romanticism, a school of thought opposed to the French Enlightenment Rationalism Napoleon was spreading. Interestingly, the Napoleonic Wars fueled the energies of both liberal and conservative opponents: in Spain, a bloody Peninsular War was fought by guerillas who wanted to return a Bourbon to the throne; in Germany people complained that they wanted more self-rule.
The Napoleonic period was an extremely complicated time. Moral right and wrong are hard to distinguish: Napoleon was a dictator, but not a particularly evil one. He encouraged many developments we today consider quite positive. The Napoleonic Wars were instigated by France, but each nation fought to protect and expand its own national interest. The wars were punctuated by constantly shifting alliances. Sometimes Prussia fought France, and sometimes it was neutral. Austria, led by the crafty Metternich, tried to improve relations with France towards the end the Napoleonic era. Russia initially opposed Napoleon, then sided with him, and then turned against him again. The only constant through the fifteen years of Napoleon's rule was the continued enmity between England and France. Instead of a war between irreconcilable values, the Napoleonic Wars were fought with essentially the same motivation driving all sides: greed. The period was typified by "Realism" in diplomacy and war, for all sides were simply trying to win whatever advantages they could.
If anyone won the Napoleonic Wars, it was Britain. Britain emerged in 1815 as a commercial powerhouse with the world's preeminent navy and a large colonial network. British industry might have provoked working-class rebellion if not for the national unity having an enemy like Napoleon provided. Blaming the hard lives of the working class on Napoleon's war mongering, Britain made it through a critical and dangerous time of its young Industrial Revolution.
The quagmire Napoleon had made of Europe was cleaned up, as much as it could be, by the Congress of Vienna (1814-1815). The resultant agreement from the two years of deliberation was undoubtedly one of the most important and complicated treaties in human history. The international order that the Congress designed was balanced enough that future rising powers could be stopped by coalitions of other powers. This made Europe fairly stable for the next century, but it also protected conservative regimes. Napoleon had spread the new liberal changes as he spread his empire; the kings and aristocrats at the Congress of Vienna figured out a way to prolong the life of the old conservative regimes a while longer. Thus, the Congress of Vienna set the stage for the coming battle between liberalism and conservatism in the following period, from 1815 to the revolutionary year 1848.