Holy Alliance in the context of "Unification of Germany"

The Russian Empire was an empire that spanned most of northern Eurasia from its establishment in November 1721 until the proclamation of the Russian Republic in September 1917. At its height in the late 19th century, it covered about 22,800,000 km (8,800,000 sq mi), roughly one-sixth of the world's landmass, making it the third-largest empire in history, behind only the British and Mongol empires. It also colonized Alaska between 1799 and 1867. The empire's 1897 census, the only one it conducted, found a population of 125.6 million with considerable ethnic, linguistic, religious, and socioeconomic diversity.

From the 10th to 17th century, the Russians had been ruled by a noble class known as the boyars, above whom was the tsar, the absolute monarch. The groundwork of the Russian Empire was laid by Ivan III who ruled from 1462 to 1505, and greatly expanded his domain, established a centralized Russian national state, and secured independence against the Tatars. His grandson, Ivan IV (r. 1533–1584), became in 1547 the first Russian monarch to be crowned tsar of all Russia. Between 1550 and 1700, the Russian state grew by an average of 35,000 km (14,000 sq mi) per year. Peter I transformed the tsardom into an empire, and fought numerous wars that turned a vast realm into a major European power. He moved the Russian capital from Moscow to the new model city of Saint Petersburg, and led a cultural revolution that introduced a modern, scientific, rationalist, and Western-oriented system. Catherine the Great (r. 1762–1796) presided over further expansion of the Russian state by conquest, colonization, and diplomacy, while continuing Peter's policy of modernization. Alexander I (r. 1801–1825) helped defeat the militaristic ambitions of Napoleon and subsequently constituted the Holy Alliance, which aimed to restrain the rise of secularism and liberalism across Europe. Russia further expanded to the west, south, and east, strengthening its position as a European power. Its victories in the Russo-Turkish Wars were later checked by defeat in the Crimean War (1853–1856), leading to a period of reform and conquests in Central Asia. Alexander II (r. 1855–1881) initiated numerous reforms, most notably the 1861 emancipation of all 23 million serfs.

The Concert of Europe was a general agreement between the great powers of 19th-century Europe to maintain the European balance of power, political boundaries, and spheres of influence. Never a perfect unity and subject to disputes and jockeying for position and influence, the Concert was an extended period of relative peace and stability in Europe following the Wars of the French Revolution and the Napoleonic Wars which had consumed the continent since the 1790s. There is considerable scholarly dispute over the exact nature and duration of the Concert. Some scholars argue that it fell apart nearly as soon as it began in the 1820s when the great powers disagreed over the handling of liberal revolts in Italy, while others argue that it lasted until the outbreak of World War I and others for points in between. For those arguing for a longer duration, there is generally agreement that the period after the Revolutions of 1848 and the Crimean War (1853–1856) represented a different phase with different dynamics than the earlier period.

The beginnings of the Concert System, known as the Congress System or the Vienna System after the Congress of Vienna (1814–1815), was dominated by the five great powers of Europe: Austria, France, Prussia, Russia, and the United Kingdom. Initially envisioning regular Congresses among the great powers to resolve potential disputes, in practice, Congresses were held on an ad hoc basis and were generally successful in preventing or localizing conflicts. The more conservative members of the Concert of Europe, members of the Holy Alliance (Russia, Austria, and Prussia), used the system to oppose revolutionary and liberal movements and weaken the forces of nationalism. The formal Congress System fell apart in the 1820s but peace between the Great Powers continued and occasional meetings reminiscent of the Congresses continued to be held at times of crisis.

The Age of Revolution is a period from the late-18th to the mid-19th centuries during which a number of significant revolutionary movements occurred in most of Europe and the Americas. The period is noted for the change from absolutist monarchies to representative governments with a written constitution, and the creation of nation states.

Influenced by the new ideas of the Enlightenment, the American Revolution (1765–1783) is usually considered the starting point of the Age of Revolution. Later revolution would be the French Revolution of 1789, the revolution that rapidly spread to the rest of Europe through its wars. In 1799, Napoleon took power in France and continued the French Revolutionary Wars by conquering most of continental Europe. Although Napoleon imposed on his conquests several modern concepts such as equality before the law, or a civil code, his rigorous military occupation triggered national rebellions, notably in Spain and Germany. After Napoleon's defeat, European great powers forged the Holy Alliance at the Congress of Vienna in 1814–15, in an attempt to prevent future revolutions, and also restored the previous monarchies. Nevertheless, Spain was considerably weakened by the Napoleonic Wars and could not control its American colonies, almost all of which proclaimed their independence between 1810 and 1820. Revolution then spread back to southern Europe in 1820, with uprisings in Portugal, Spain, Italy, and Greece. Continental Europe was shaken by two similar revolutionary waves in 1830 and 1848, also called the Spring of Nations. The democratic demands of the revolutionaries often merged with independence or national unification movements, such as in Italy, Germany, Poland, Hungary, etc. The violent repression of the Spring of Nations marked the end of the era.