The history of Russia begins with the histories of the East Slavs. The traditional start date of specifically Russian history is the establishment of the Rus' state in the north in the year 862, ruled by Varangians. In 882, Prince Oleg of Novgorod seized Kiev, uniting the northern and southern lands of the Eastern Slavs under one authority, moving the governance center to Kiev by the end of the 10th century, and maintaining northern and southern parts with significant autonomy from each other. The state adopted Christianity from the Byzantine Empire in 988, beginning the synthesis of Byzantine and Slavic cultures that defined Russian culture for the next millennium. Kievan Rus' ultimately disintegrated as a state due to the Mongol invasions in 1237–1240. After the 13th century, Moscow emerged as a significant political and cultural force, driving the unification of Russian territories. By the end of the 15th century, many of the petty principalities around Moscow had been united with the Grand Duchy of Moscow, which took full control of its own sovereignty under Ivan the Great.

Ivan the Terrible transformed the Grand Duchy into the Tsardom of Russia in 1547. However, the death of Ivan's son Feodor I without issue in 1598 created a succession crisis and led Russia into a period of chaos and civil war known as the Time of Troubles, ending with the coronation of Michael Romanov as the first Tsar of the Romanov dynasty in 1613. During the rest of the seventeenth century, Russia completed the exploration and conquest of Siberia, claiming lands as far as the Pacific Ocean by the end of the century. Domestically, Russia faced numerous uprisings of the various ethnic groups under their control, as exemplified by the Cossack leader Stenka Razin, who led a revolt in 1670–1671. In 1721, in the wake of the Great Northern War, Tsar Peter the Great renamed the state as the Russian Empire; he is also noted for establishing St. Petersburg as the new capital of his Empire, and for his introducing Western European culture to Russia. In 1762, Russia came under the control of Catherine the Great, who continued the westernizing policies of Peter the Great, and ushered in the era of the Russian Enlightenment. Catherine's grandson, Alexander I, repulsed an invasion by the French Emperor Napoleon, leading Russia into the status of one of the great powers.

Peasant revolts intensified during the nineteenth century, culminating with Alexander II abolishing Russian serfdom in 1861. In the following decades, reform efforts such as the Stolypin reforms of 1906–1914, the constitution of 1906, and the State Duma (1906–1917) attempted to open and liberalize the economy and political system, but the emperors refused to relinquish autocratic rule and resisted sharing their power. A combination of economic breakdown, mismanagement over Russia's involvement in World War I, and discontent with the autocratic system of government triggered the Russian Revolution in 1917. The end of the monarchy initially brought into office a coalition of liberals and moderate socialists, but their failed policies led to the October Revolution. In 1922, Soviet Russia, along with the Ukrainian SSR, Byelorussian SSR, and Transcaucasian SFSR signed the Treaty on the Creation of the USSR, officially merging all four republics to form the Soviet Union as a single state. Between 1922 and 1991 the history of Russia essentially became the history of the Soviet Union. During this period, the Soviet Union was one of the victors in World War II after recovering from a surprise invasion in 1941 by Nazi Germany and its collaborators, which had previously signed a non-aggression pact with the Soviet Union. The Soviet Union's network of satellite states in Eastern Europe, which were brought into its sphere of influence in the closing stages of World War II, helped the country become a superpower competing with fellow superpower the United States and other Western countries in the Cold War.

By the mid-1980s, with the weaknesses of Soviet economic and political structures becoming acute, Mikhail Gorbachev embarked on major reforms, which eventually led to the weakening of the communist party and dissolution of the Soviet Union, leaving Russia again on its own and marking the start of the history of post-Soviet Russia. The Russian Soviet Federative Socialist Republic renamed itself as the Russian Federation and became the primary successor state to the Soviet Union. Russia retained its nuclear arsenal but lost its superpower status. Scrapping the central planning and state-ownership of property of the Soviet era in the 1990s, new leaders, led by President Vladimir Putin, took political and economic power after 2000 and engaged in an assertive foreign policy. Coupled with economic growth, Russia has since regained significant global status as a world power. Russia's 2014 annexation of the Crimean Peninsula led to economic sanctions imposed by the United States and the European Union. Russia's 2022 invasion of Ukraine led to significantly expanded sanctions. Under Putin's leadership, corruption in Russia is rated as the worst in Europe, and Russia's human rights situation has been increasingly criticized by international observers.

The first human settlement on the territory of Russia dates back to the Oldowan period in the early Lower Paleolithic. About 2 million years ago, representatives of Homo erectus migrated from Western Asia to the North Caucasus (archaeological site of Kermek [ru] on the Taman Peninsula). At Bogatyri/Sinyaya balka [ru], in a skull of Elasmotherium caucasicum, which lived 1.5–1.2 million years ago, a stone tool was found. 1.5-million-year-old Oldowan flint tools have been discovered in the Dagestan Akusha region of the north Caucasus, demonstrating the presence of early humans in the territory of present-day Russia.

Fossils of Denisovans in Russia date to about 110,000 years ago. DNA from a bone fragment found in Denisova Cave, belonging to a female who died about 90,000 years ago, shows that she was a hybrid of a Neanderthal mother and a Denisovan father. Russia was also home to some of the last surviving Neanderthals - the partial skeleton of a Neanderthal infant in Mezmaiskaya cave in Adygea showed a carbon-dated age of only 45,000 years. In 2008, Russian archaeologists from the Institute of Archaeology and Ethnology of Novosibirsk, working at the site of Denisova Cave in the Altai Mountains of Siberia, uncovered a 40,000-year-old small bone fragment from the fifth finger of a juvenile hominin, which DNA analysis revealed to be a previously unknown species of human, which was named the Denisova hominin.

The first trace of Homo sapiens on the large expanse of Russian territory dates back to 45,000 years, in central Siberia (Ust'-Ishim man). The discovery of some of the earliest evidence for the presence of anatomically modern humans found anywhere in Europe was reported in 2007 from the Kostenki archaeological site near the Don River in Russia (dated to at least 40,000 years ago) and at Sungir (34,600 years ago). Humans reached Arctic Russia (Mamontovaya Kurya) by 40,000 years ago.

During the prehistoric eras the vast steppes of Southern Russia were home to tribes of nomadic pastoralists. (In classical antiquity, the Pontic Steppe was known as "Scythia".) Remnants of these long-gone steppe cultures were discovered in the course of the 20th century in such places as Ipatovo, Sintashta, Arkaim, and Pazyryk.

In the later part of the 8th century BCE, Greek merchants brought classical civilization to the trade emporiums in Tanais and Phanagoria. Gelonus was described by Herodotus as a huge (Europe's biggest) earth- and wood-fortified grad inhabited around 500 BC by Heloni and Budini. In 513 BC, the king of the Achaemenid Empire, Darius I, would launch a military campaign around the Black Sea into Scythia, modern-day Ukraine, eventually reaching the Tanais river (now known as the Don).

Greeks, mostly from the city-state of Miletus, would colonize large parts of modern-day Crimea and the Sea of Azov during the seventh and sixth centuries BC, eventually unifying into the Bosporan Kingdom by 480 BC, and would be incorporated into the large Kingdom of Pontus in 107 BC. The Kingdom would eventually be conquered by the Roman Republic, and the Bosporan Kingdom would become a client state of the Roman Empire. At about the 2nd century AD Goths migrated to the Black Sea, and in the 3rd and 4th centuries AD, a semi-legendary Gothic kingdom of Oium existed in Southern Russia until it was overrun by Huns. Between the 3rd and 6th centuries AD, the Bosporan Kingdom was also overwhelmed by successive waves of nomadic invasions, led by warlike tribes which would often move on to Europe, as was the case with the Huns and Turkish Avars.

In the second millennium BC, the territories between the Kama and the Irtysh Rivers were the home of a Proto-Uralic-speaking population that had contacts with Proto-Indo-European speakers from the south. The woodland population is the ancestor of the modern Ugrian inhabitants of Trans-Uralia. Other researchers say that the Khanty people originated in the south Ural steppe and moved northwards into their current location about 500 AD.

A Turkic people, the Khazars, ruled the lower Volga basin steppes between the Caspian and Black Seas through to the 8th century. Noted for their laws, tolerance, and cosmopolitanism, the Khazars were the main commercial link between the Baltic and the Muslim Abbasid empire centered in Baghdad. They were important allies of the Eastern Roman Empire, and waged a series of successful wars against the Arab Caliphates. In the 8th century, the Khazars embraced Judaism.

Some of the ancestors of the modern Russians were the Slavic tribes, whose original home is thought by some scholars to have been the Pripet Marshes. The Early East Slavs gradually settled Western Russia in two waves: one moving from Kiev (present-day Ukraine) towards present-day Suzdal and Murom and another from Polotsk (present-day Belarus) towards Novgorod and Rostov.

From the 7th century onwards, East Slavs constituted the bulk of the population in Western Russia and slowly conquered and assimilated the native Finnic and Baltic tribes, such as the Merya, the Muromians, and the Meshchera.

Scandinavian Norsemen, known as Vikings in Western Europe and Varangians in the East, combined piracy and trade throughout Northern Europe. In the mid-9th century, they began to venture along the waterways from the eastern Baltic to the Black and Caspian Seas. According to the legendary Calling of the Varangians, recorded in several Rus' chronicles such as the Novgorod First Chronicle and Primary Chronicle, the Varangians Rurik, Sineus and Truvor were invited in the 860s to restore order in three towns – either Novgorod (most texts) or Staraya Ladoga (Hypatian Codex); Beloozero; and Izborsk (most texts) or "Slovensk" (Pskov Third Chronicle), respectively. Their successors allegedly moved south and extended their authority to Kiev, which had been previously dominated by the Khazars.

Thus, the first East Slavic state, Rus', emerged in the 9th century along the Dnieper River valley. A coordinated group of princely states with a common interest in maintaining trade along the river routes, Kievan Rus' controlled the trade route for furs, wax, and slaves between Scandinavia and the Byzantine Empire along the Volkhov and Dnieper Rivers.

By the end of the 10th century, the minority Norse military aristocracy had merged with the native Slavic population, which also absorbed Greek Christian influences in the course of the multiple campaigns to loot Tsargrad, or Constantinople. One such campaign claimed the life of the foremost Slavic druzhina leader, Svyatoslav I, who was renowned for having crushed the power of the Khazars on the Volga.

Kievan Rus' is important for its introduction of a Slavic variant of the Eastern Orthodox religion, dramatically deepening a synthesis of Byzantine and Slavic cultures that defined Russian culture for the next thousand years. The region adopted Christianity in 988 by the official act of public baptism of Kiev inhabitants by Prince Vladimir I. Some years later the first code of laws, Russkaya Pravda, was introduced by Yaroslav the Wise. From the onset, the Kievan princes followed the Byzantine example and kept the Church dependent on them.

By the 11th century, particularly during the reign of Yaroslav the Wise, Kievan Rus' displayed an economy and achievements in architecture and literature superior to those that then existed in the western part of the continent. Compared with the languages of European Christendom, the Russian language was little influenced by the Greek and Latin of early Christian writings. This was because Church Slavonic was used directly in liturgy instead. A nomadic Turkic people, the Kipchaks (also known as the Cumans), replaced the earlier Pechenegs as the dominant force in the south steppe regions neighbouring to Rus' at the end of the 11th century and founded a nomadic state in the steppes along the Black Sea (Desht-e-Kipchak). Repelling their regular attacks, especially in Kiev, was a heavy burden for the southern areas of Rus'. The nomadic incursions caused a massive influx of Slavs to the safer, heavily forested regions of the north, particularly to the area known as Zalesye.

Kievan Rus' ultimately disintegrated as a state because of in-fighting between members of the princely family that ruled it collectively. Kiev's dominance waned, to the benefit of Vladimir-Suzdal in the north-east, Novgorod in the north, and Halych-Volhynia in the south-west. Conquest by the Mongol Golden Horde in the 13th century was the final blow. Kiev was destroyed. Halych-Volhynia would eventually be absorbed into the Polish–Lithuanian Commonwealth, while the Mongol-dominated Vladimir-Suzdal and independent Novgorod Republic, two regions on the periphery of Kiev, would establish the basis for the modern Russian nation.

The invading Mongols accelerated the fragmentation of the Rus'. In 1223, the disunited southern princes faced a Mongol raiding party at the Kalka River and were soundly defeated. In 1237–1238 the Mongols burnt down the city of Vladimir (4 February 1238) and other major cities of northeast Russia, routed the Russians at the Sit' River, and then moved west into Poland and Hungary. By then they had conquered most of the Russian principalities. Only the Novgorod Republic escaped occupation and continued to flourish in the orbit of the Hanseatic League.

The impact of the Mongol invasion on the territories of Kievan Rus' was uneven. The advanced city culture was almost completely destroyed. As older centers such as Kiev and Vladimir never recovered from the devastation of the initial attack, the new cities of Moscow, Tver and Nizhny Novgorod began to compete for hegemony in the Mongol-dominated Rus' principalities under the suzerainty of the Golden Horde. Although a coalition of Rus' princes led by Dmitry Donskoy defeated Mongol warlord Mamai at Kulikovo in 1380, forces of the new khan Tokhtamysh and his Rus' allies immediately sacked Moscow in 1382 as punishment for resisting Mongol authority. Mongol domination of the Rus' principalities, along with tax collection by various overlords such as the Crimean Khans, continued into the early 16th century, despite later claims of Muscovite bookmen that the indecisive standoff at the Ugra in 1480 had signified "the end of the Tatar yoke" and the "liberation of Russia".

The Mongols dominated the lower reaches of the Volga and held Russia in sway from their western capital at Sarai, one of the largest cities of the medieval world. The princes had to pay tribute to the Mongols of the Golden Horde, commonly called Tatars; but in return they received charters authorizing them to act as deputies to the khans. In general, the princes were allowed considerable freedom to rule as they wished, while the Russian Orthodox Church even experienced a spiritual revival.

The Mongols left their impact on the Russians in such areas as military tactics and transportation. Under Mongol occupation, Muscovy also developed its postal road network, census, fiscal system, and military organization.

At the same time, Prince of Novgorod, Alexander Nevsky, managed to repel the offensive of the Northern Crusades against Novgorod from the West. Despite this, becoming the Grand Prince, Alexander declared himself a vassal to the Golden Horde, not having the strength to resist its power.

Daniil Aleksandrovich, the youngest son of Alexander Nevsky, founded the principality of Moscow (known as Muscovy in English), which first cooperated with and ultimately expelled the Tatars from Russia. Well-situated in the central river system of Russia and surrounded by protective forests and marshes, Moscow was at first only a vassal of Vladimir, but soon it absorbed its parent state.

A major factor in the ascendancy of Moscow was the cooperation of its rulers with the Mongol overlords, who granted them the title of Grand Prince of Moscow and made them agents for collecting the Tatar tribute from the Russian principalities. The principality's prestige was further enhanced when it became the center of the Russian Orthodox Church. Its head, the Metropolitan, fled from Kiev to Vladimir in 1299 and a few years later established the permanent headquarters of the Church in Moscow under the original title of Kiev Metropolitan.

By the middle of the 14th century, the power of the Mongols was declining, and the Grand Princes felt able to openly oppose the Mongol yoke. In 1380, at Battle of Kulikovo on the Don River, the Mongols were defeated, and although this hard-fought victory did not end Tatar rule of Russia, it did bring great fame to the Grand Prince Dmitry Donskoy. Moscow's leadership in Russia was now firmly based and by the middle of the 14th century its territory had greatly expanded through purchase, war, and marriage.

In the 15th century, the grand princes of Moscow continued to consolidate Russian land to increase their population and wealth. The most successful practitioner of this process was Ivan III, who laid the foundations for a Russian national state. Ivan competed with his powerful northwestern rival, the Grand Duchy of Lithuania, for control over some of the semi-independent Upper Principalities in the upper Dnieper and Oka River basins.

Through the defections of some princes, border skirmishes, and a long war with the Novgorod Republic, Ivan III was able to annex Novgorod and Tver. As a result, the Grand Duchy of Moscow tripled in size under his rule. During his conflict with Pskov, a monk named Filofei (Philotheus of Pskov) composed a letter to Ivan III, with the prophecy that the latter's kingdom would be the Third Rome. The Fall of Constantinople and the death of the last Greek Orthodox Christian emperor contributed to this new idea of Moscow as New Rome and the seat of Orthodox Christianity, as did Ivan's 1472 marriage to Byzantine Princess Sophia Palaiologina.

Under Ivan III, the first central government bodies were created in Russia: Prikaz. The Sudebnik was adopted, the first set of laws since the 11th century. The double-headed eagle was adopted as the coat of arms of Russia.

Ivan proclaimed his absolute sovereignty over all Russian princes and nobles. Refusing further tribute to the Tatars, Ivan initiated a series of attacks that opened the way for the complete defeat of the declining Golden Horde, now divided into several Khanates and hordes. Ivan and his successors sought to protect the southern boundaries of their domain against attacks of the Crimean Tatars and other hordes. To achieve this aim, they sponsored the construction of the Great Abatis Belt and granted manors to nobles, who were obliged to serve in the military. The manor system provided a basis for an emerging cavalry-based army.

In this way, internal consolidation accompanied outward expansion of the state. By the 16th century, the rulers of Moscow considered the entire Russian territory their collective property. Various semi-independent princes still claimed specific territories, but Ivan III forced the lesser princes to acknowledge the grand prince of Moscow and his descendants as unquestioned rulers with control over military, judicial, and foreign affairs. Gradually, the Russian ruler emerged as a powerful, autocratic ruler, a tsar. The first Russian ruler to officially crown himself "Tsar" was Ivan IV.

Ivan III tripled the territory of his state, ended the dominance of the Golden Horde over the Rus', renovated the Moscow Kremlin, and laid the foundations of the Russian state. Biographer Fennell concludes that his reign was "militarily glorious and economically sound," and especially points to his territorial annexations and his centralized control over local rulers. However, Fennell argues that his reign was also "a period of cultural depression and spiritual barrenness. Freedom was stamped out within the Russian lands. By his bigoted anti-Catholicism Ivan brought down the curtain between Russia and the west. For the sake of territorial aggrandizement he deprived his country of the fruits of Western learning and civilization."

The development of the Tsar's autocratic powers reached a peak during the reign of Ivan IV (1547–1584), known as "Ivan the Terrible". He strengthened the position of the monarch to an unprecedented degree, as he ruthlessly subordinated the nobles to his will, exiling or executing many on the slightest provocation. Nevertheless, Ivan is often seen as a farsighted statesman who reformed Russia as he promulgated a new code of laws (Sudebnik of 1550), established the first Russian feudal representative body (Zemsky Sobor), curbed the influence of the clergy, and introduced local self-management in rural regions. Tsar also created the first regular army in Russia: Streltsy.

His long Livonian War (1558–1583) for control of the Baltic coast and access to the sea trade ultimately proved a costly failure. Ivan managed to annex the Khanates of Kazan, Astrakhan, and Siberia. These conquests complicated the migration of aggressive nomadic hordes from Asia to Europe via the Volga and Urals. Through these conquests, Russia acquired a significant Muslim Tatar population and emerged as a multiethnic and multiconfessional state. Also around this period, the mercantile Stroganov family established a firm foothold in the Urals and recruited Russian Cossacks to colonise Siberia.

In the later part of his reign, Ivan divided his realm in two. In the zone known as the oprichnina, Ivan's followers carried out a series of bloody purges of the feudal aristocracy (whom he suspected of treachery after prince Andrey Kurbsky's betrayal), culminating in the Massacre of Novgorod in 1570. This combined with the military losses, epidemics, and poor harvests so weakened Russia that the Crimean Tatars were able to sack central Russian regions and burn down Moscow in 1571. However, in 1572 the Russians defeated the Crimean Tatar army at the Battle of Molodi and Ivan abandoned the oprichnina.

At the end of Ivan IV's reign the Polish–Lithuanian and Swedish armies carried out a powerful intervention in Russia, devastating its northern and northwest regions.

The death of Ivan's childless son Feodor was followed by a period of civil wars and foreign intervention known as the Time of Troubles (1606–13). Extremely cold summers (1601–1603) wrecked crops, which led to the Russian famine of 1601–1603 and increased the social disorganization. Boris Godunov's reign ended in chaos, civil war combined with foreign intrusion, devastation of many cities and depopulation of the rural regions. The country rocked by internal chaos also attracted several waves of interventions by the Polish–Lithuanian Commonwealth. During the Polish–Muscovite War (1605–1618), Polish–Lithuanian forces reached Moscow and installed the impostor False Dmitriy I in 1605, then supported False Dmitry II in 1607. The decisive moment came when a combined Russian-Swedish army was routed by the Polish forces under hetman Stanisław Żółkiewski at the Battle of Klushino on 4 July [O.S. 24 June] 1610. As the result of the battle, the Seven Boyars, a group of Russian nobles, deposed the tsar Vasily Shuysky on 27 July [O.S. 17 July] 1610, and recognized the Polish prince Władysław IV Vasa as the Tsar of Russia on 6 September [O.S. 27 August] 1610. The Poles occupied Moscow on 21 September [O.S. 11 September] 1610. Moscow revolted but riots there were brutally suppressed and the city was set on fire.

The crisis provoked a patriotic national uprising against the invasion, both in 1611 and 1612. A volunteer army, led by the merchant Kuzma Minin and prince Dmitry Pozharsky, expelled the foreign forces from the capital on 4 November [O.S. 22 October] 1612.

The Russian statehood survived the "Time of Troubles" and the rule of weak or corrupt Tsars because of the strength of the government's central bureaucracy. Government functionaries continued to serve, regardless of the ruler's legitimacy or the faction controlling the throne. However, the Time of Troubles caused the loss of much territory to the Polish–Lithuanian Commonwealth in the Russo-Polish war, as well as to the Swedish Empire in the Ingrian War.

In February 1613, after the chaos and expulsion of the Poles from Moscow, a national assembly elected Michael Romanov, the young son of Patriarch Filaret, to the throne. The Romanov dynasty ruled Russia until 1917.

The immediate task of the new monarch was to restore peace. Fortunately for Moscow, its major enemies, the Polish–Lithuanian Commonwealth and Sweden, were engaged in a bitter conflict with each other, which provided Russia the opportunity to make peace with Sweden in 1617 and to sign a truce with the Polish–Lithuanian Commonwealth in 1619.

Recovery of lost territories began in the mid-17th century, when the Khmelnitsky Uprising (1648–1657) in Ukraine against Polish rule brought about the Treaty of Pereyaslav between Russia and the Ukrainian Cossacks. In the treaty, Russia granted protection to the Cossacks state in Left-bank Ukraine, formerly under Polish control. This triggered a prolonged Russo-Polish War (1654–1667), which ended with the Treaty of Andrusovo, where Poland accepted the loss of Left-bank Ukraine, Kiev and Smolensk. The Russian conquest of Siberia, begun at the end of the 16th century, continued in the 17th century. By the end of the 1640s, the Russians reached the Pacific Ocean, the Russian explorer Semyon Dezhnev, discovered the strait between Asia and America. Russian expansion in the Far East faced resistance from Qing China. After the war between Russia and China, the Treaty of Nerchinsk was signed, delimiting the territories in the Amur region.

Rather than risk their estates in more civil war, the boyars cooperated with the first Romanovs, enabling them to finish the work of bureaucratic centralization. Thus, the state required service from both the old and the new nobility, primarily in the military. In return, the tsars allowed the boyars to complete the process of enserfing the peasants.

In the preceding century, the state had gradually curtailed peasants' rights to move from one landlord to another. With the state now fully sanctioning serfdom, runaway peasants became state fugitives, and the power of the landlords over the peasants "attached" to their land had become almost complete. Together, the state and the nobles placed an overwhelming burden of taxation on the peasants, whose rate was 100 times greater in the mid-17th century than it had been a century earlier. Likewise, middle-class urban tradesmen and craftsmen were assessed taxes, and were forbidden to change residence. All segments of the population were subject to military levy and special taxes.

Riots among peasants and citizens of Moscow at this time were endemic and included the Salt Riot (1648), Copper Riot (1662), and the Moscow Uprising (1682). By far the greatest peasant uprising in 17th-century Europe erupted in 1667. As the free settlers of South Russia, the Cossacks, reacted against the growing centralization of the state, serfs escaped from their landlords and joined the rebels. The Cossack leader Stenka Razin led his followers up the Volga River, inciting peasant uprisings and replacing local governments with Cossack rule. The tsar's army finally crushed his forces in 1670; a year later Stenka was captured and beheaded. Yet, less than half a century later, the strains of military expeditions produced another revolt in Astrakhan, ultimately subdued.

Much of Russia's expansion occurred in the 17th century, culminating in the first Russian colonisation of the Pacific in the mid-17th century, the Russo-Polish War (1654–1667) that incorporated left-bank Ukraine, and the Russian conquest of Siberia. Poland was divided in the 1790–1815 era, with much of the land and population going to Russia. Most of the 19th century growth came from adding territory in Asia, south of Siberia.

Year	Population of Russia (millions)	Notes
1720	15.5	includes new Baltic & Polish territories
1795	37.6	includes part of Poland
1812	42.8	includes Finland
1816	73.0	includes Congress Poland, Bessarabia
1914	170.0	includes new Asian territories

Peter the Great (Peter I, 1672–1725) brought centralized autocracy into Russia and played a major role in bringing his country into the European state system. Russia was now the largest country in the world, stretching from the Baltic Sea to the Pacific Ocean. The vast majority of the land was unoccupied, and travel was slow. Much of its expansion had taken place in the 17th century, culminating in the first Russian settlement of the Pacific in the mid-17th century, the reconquest of Kiev, and the pacification of the Siberian tribes. However, a population of only 14 million was stretched across this vast landscape. With a short growing season, grain yields trailed behind those in the West and potato farming was not yet widespread. As a result, the great majority of the population workforce was occupied with agriculture. Russia remained isolated from the sea trade and its internal trade, communication and manufacturing were seasonally dependent.

Peter reformed the Russian army and created the Russian navy. Peter's first military efforts were directed against the Ottoman Turks. His aim was to establish a Russian foothold on the Black Sea by taking the town of Azov. His attention then turned to the north. Peter still lacked a secure northern seaport except at Archangel on the White Sea, whose harbor was frozen nine months a year. Access to the Baltic was blocked by Sweden, whose territory enclosed it on three sides. Peter's ambitions for a "window to the sea" led him in 1699 to make a secret alliance with the Polish–Lithuanian Commonwealth and Denmark against Sweden resulting in the Great Northern War.

The war ended in 1721 when an exhausted Sweden sued for peace with Russia. Peter acquired four provinces situated south and east of the Gulf of Finland, thus securing his coveted access to the sea. There, in 1703, he had already founded the city that was to become Russia's new capital, Saint Petersburg. Russian intervention in the Commonwealth marked, with the Silent Sejm, the beginning of a 200-year domination of that region by the Russian Empire. In celebration of his conquests, Peter assumed the title of emperor, and the Russian Tsardom officially became the Russian Empire in 1721.

Peter re-organized his government based on the latest Western models, molding Russia into an absolutist state. He replaced the old boyar Duma (council of nobles) with a Senate, in effect a supreme council of state. The countryside was also divided into new provinces and districts. Peter told the senate that its mission was to collect taxes. In turn tax revenues tripled over the course of his reign.

Administrative Collegia (ministries) were established in St. Petersburg, to replace the old governmental departments. In 1722, Peter promulgated his famous Table of ranks. As part of the government reform, the Orthodox Church was partially incorporated into the country's administrative structure, in effect making it a tool of the state. Peter abolished the patriarchate and replaced it with a collective body, the Holy Synod, led by a lay government official. Peter continued and intensified his predecessors' requirement of state service for all nobles.

By then, the once powerful Persian Safavid Empire to the south was heavily declining. Taking advantage, Peter launched the Russo-Persian War (1722–1723), known as "The Persian Expedition of Peter the Great" by Russian histographers, in order to be the first Russian emperor to establish Russian influence in the Caucasus and Caspian Sea region. After considerable success and the capture of many provinces and cities in the Caucasus and northern mainland Persia, the Safavids were forced to hand over the territories to Russia. However, by 12 years later, all the territories were ceded back to Persia, which was now led by the charismatic military genius Nader Shah, as part of the Treaty of Resht and Treaty of Ganja and the Russo-Persian alliance against the Ottoman Empire, the common neighbouring rivalling enemy.

Peter the Great died in 1725, leaving an unsettled succession, but Russia had become a great power by the end of his reign. Peter I was succeeded by his second wife, Catherine I (1725–1727), who was merely a figurehead for a powerful group of high officials, then by his minor grandson, Peter II (1727–1730), then by his niece, Anna (1730–1740), daughter of Tsar Ivan V. The heir to Anna was soon deposed in a coup and Elizabeth, daughter of Peter I, ruled from 1741 to 1762. During her reign, Russia took part in the Seven Years' War.

Nearly 40 years passed before a comparably ambitious ruler appeared. Catherine II, "the Great" (r. 1762–1796), was a German princess who married the German heir to the Russian crown. Catherine overthrew him in a coup in 1762, becoming queen regnant. Catherine enthusiastically supported the ideals of The Enlightenment, thus earning the status of an enlightened despot. She patronized the arts, science and learning. She contributed to the resurgence of the Russian nobility that began after the death of Peter the Great. Catherine promulgated the Charter to the Gentry reaffirming rights and freedoms of the Russian nobility and abolishing mandatory state service. She seized control of all the church lands, drastically reduced the size of the monasteries, and put the surviving clergy on a tight budget.

Catherine spent heavily to promote an expansive foreign policy. She extended Russian political control over the Polish–Lithuanian Commonwealth with actions, including the support of the Targowica Confederation. The cost of her campaigns, plus the oppressive social system that required serfs to spend almost all their time laboring on the land of their lords, provoked a major peasant uprising in 1773. Inspired by a Cossack named Yemelyan Pugachev, with the emphatic cry of "Hang all the landlords!", the rebels threatened to take Moscow until Catherine crushed the rebellion. Like the other enlightened despots of Europe, Catherine made certain of her own power and formed an alliance with the nobility.

Catherine successfully waged two wars (1768–1774, 1787–1792) against the decaying Ottoman Empire and advanced Russia's southern boundary to the Black Sea. In 1775 she liquidated the Zaporozhian Sich, and on the former lands of the Ukrainian Cossacks in the places of theirs settlements was created Novorossiya Governorate, in which new cities were formed: Yekaterinoslav (1776), Yelisavetgrad, Kherson (1778), Odessa (1794). Russia annexed Crimea in 1783 and created the Black Sea fleet. Then, by allying with the rulers of Austria and Prussia, she incorporated the territories of the Polish–Lithuanian Commonwealth, where after a century of Russian rule non-Catholic, mainly Orthodox population prevailed during the Partitions of Poland, pushing the Russian frontier westward into Central Europe.

In accordance to Russia's treaty with the Georgians to protect them against any new invasion of their Persian suzerains and further political aspirations, Catherine waged a new war against Persia in 1796 after they had again invaded Georgia and established rule over it about a year prior, and had expelled the newly established Russian garrisons in the Caucasus.

In 1798–1799, Russian troops participated in the anti-French coalition, the troops under the command of Alexander Suvorov defeated the French in Northern Italy.

Russian emperors of the 18th century professed the ideas of Enlightened absolutism. However, Westernization and modernization affected only the upper classes of Russian society, while the bulk of the population, consisting of peasants, remained in a state of serfdom. Powerful Russians resented their privileged positions and alien ideas. The backlash was especially severe after the Napoleonic wars. It produced a powerful anti-western campaign that "led to a wholesale purge of Western specialists and their Russian followers in universities, schools, and government service". The mid-18th century was marked by the emergence of higher education in Russia. The first two major universities Saint Petersburg State University and Moscow State University were opened. Russian exploration of Siberia and the Far East continued. Great Northern Expedition laid the foundation for the development of Alaska by the Russians. By the end of the 18th century, Alaska became a Russian colony (Russian America). In the early 19th century, Alaska was used as a base for the First Russian circumnavigation. In 1819–1821, Russian sailors discovered Antarctica during an Antarctic expedition.

Russia was in a continuous state of financial crisis. While revenue rose from 9 million rubles in 1724 to 40 million in 1794, expenses grew more rapidly, reaching 49 million in 1794. The budget was allocated 46% to the military, 20% to government economic activities, 12% to administration, and 9% for the Imperial Court in St. Petersburg. The deficit required borrowing, primarily from Amsterdam; 5% of the budget was allocated to debt payments. Paper money was issued to pay for expensive wars, thus causing inflation. 18th-century Russia remained "a poor, backward, overwhelmingly agricultural, and illiterate country".

By the time of her death in 1796, Catherine's expansionist policy had made Russia a major European power. Alexander I continued this policy, wresting Finland from the weakened kingdom of Sweden in 1809 and Bessarabia from the Ottomans in 1812. His key advisor was a Polish nobleman Adam Jerzy Czartoryski.

After Russian armies liberated allied Georgia from Persian occupation in 1802, they clashed with Persia over control and consolidation over Georgia, as well as the Iranian territories that comprise modern-day Azerbaijan and Dagestan. They also became involved in the Caucasian War against the Caucasian Imamate and Circassia. In 1813, the war with Persia concluded with a Russian victory, forcing Qajar Iran to cede swaths of its territories in the Caucasus to Russia, which drastically increased its territory in the region. To the south-west, Russia tried to expand at the expense of the Ottoman Empire, using Georgia at its base for the Caucasus and Anatolian front.

In European policy, Alexander I switched Russia back and forth four times in 1804–1812 from neutral peacemaker to anti-Napoleon to an ally of Napoleon, winding up in 1812 as Napoleon's enemy. In 1805, he joined Britain in the War of the Third Coalition against Napoleon, but after the massive defeat at the Battle of Austerlitz he switched and formed an alliance with Napoleon by the Treaty of Tilsit (1807) and joined Napoleon's Continental System. He fought a small-scale naval war against Britain, 1807–1812.

The alliance collapsed by 1810. Russia's economy had been hurt by Napoleon's Continental System, which cut off trade with Britain. As Esdaile notes, "Implicit in the idea of a Russian Poland was, of course, a war against Napoleon". Schroeder says Poland was the root cause of the conflict but Russia's refusal to support the Continental System was also a factor.

The invasion of Russia was a catastrophe for Napoleon and his 450,000 invasion troops. One major battle was fought at Borodino; casualties were very high, but it was indecisive, and Napoleon was unable to engage and defeat the Russian armies. He tried to force the Tsar to terms by capturing Moscow at the onset of winter, even though he had lost most of his men. Instead, the Russians retreated, burning crops and food supplies in a scorched earth policy that multiplied Napoleon's logistic problems: 85%–90% of Napoleon's soldiers died from disease, cold, starvation or ambush by peasant guerrillas. As Napoleon's forces retreated, Russian troops pursued them into Central and Western Europe, defeated Napoleon's army in the Battle of the Nations and finally captured Paris. Of a total population of around 43 million people, Russia lost about 1.5 million in the year 1812; of these about 250,000 to 300,000 were soldiers and the rest peasants and serfs.

After the defeat of Napoleon, Alexander presided over the redrawing of the map of Europe at the Congress of Vienna (1814–1815), which made him the king of Congress Poland. He formed the Holy Alliance with Austria and Prussia, to suppress revolutionary movements in Europe that he saw as immoral threats to legitimate Christian monarchs. He helped Austria's Klemens von Metternich in suppressing all national and liberal movements.

Although the Russian Empire would play a leading role on behalf of conservatism as late as 1848, its retention of serfdom precluded economic progress of any significant degree. As West European economic growth accelerated during the Industrial Revolution, sea trade and colonialism which had begun in the second half of the 18th century, Russia began to lag ever farther behind, undermining its ability to field strong armies.

Russia's great power status obscured the inefficiency of its government, the isolation of its people, and its economic backwardness. Following the defeat of Napoleon, Alexander I was willing to discuss constitutional reforms, and though a few were introduced, no thoroughgoing changes were attempted.

The tsar was succeeded by his younger brother, Nicholas I (1825–1855), who at the onset of his reign was confronted with an uprising. The background of this revolt lay in the Napoleonic Wars, when a number of well-educated Russian officers traveled in Europe in the course of the military campaigns, where their exposure to the liberalism of Western Europe encouraged them to seek change on their return. The result was the Decembrist Revolt (December 1825), the work of a small circle of liberal nobles and army officers who wanted to install Nicholas' brother as a constitutional monarch. But the revolt was easily crushed, leading Nicholas to turn away from liberal reforms and champion the reactionary doctrine "Orthodoxy, Autocracy, and Nationality".

In 1826–1828, Russia fought another war against Persia. Russia lost almost all of its recently consolidated territories during the first year but regained them and won the war on highly favourable terms. At the 1828 Treaty of Turkmenchay, Russia gained Armenia, Nakhchivan, Nagorno-Karabakh, Azerbaijan, and Iğdır. In the 1828–1829 Russo-Turkish War Russia invaded northeastern Anatolia and occupied the strategic Ottoman towns of Erzurum and Gümüşhane and, posing as protector and saviour of the Greek Orthodox population, received extensive support from the region's Pontic Greeks. After a brief occupation, the Russian imperial army withdrew into Georgia. By the 1830s, Russia had conquered all Persian territories and major Ottoman territories in the Caucasus.

In 1831, Nicholas crushed the November Uprising in Poland. The Russian autocracy gave Polish artisans and gentry reason to rebel in 1863 by assailing the national core values of language, religion, and culture. The resulting January Uprising was a massive Polish revolt, which also was crushed. France, Britain and Austria tried to intervene in the crisis but were unable. The Russian patriotic press used the Polish uprising to unify the Russian nation, claiming it was Russia's God-given mission to save Poland and the world. Poland was punished by losing its distinctive political and judicial rights, with Russianization imposed on its schools and courts.

Tsar Nicholas I (reigned 1825–1855) lavished attention on his army. In a nation of 60–70 million people, it included a million men. They had outdated equipment and tactics, but the tsar took pride in its smartness on parade. The cavalry horses, for example, were only trained in parade formations, and did poorly in battle. He put generals in charge of most of his civilian agencies regardless of their qualifications. The Army became the vehicle of upward social mobility for noble youths from non-Russian areas, such as Poland, the Baltic, Finland and Georgia. On the other hand, many miscreants, petty criminals and undesirables were punished by local officials by enlisting them for life in the Army. Village oligarchies controlled employment, conscription for the army, and local patronage; they blocked reforms and sent the most unpromising peasant youth to the army. The conscription system was unpopular with people, as was the practice of forcing peasants to house the soldiers for six months of the year.

Finally the Crimean War at the end of his reign showed the world that Russia was militarily weak, technologically backward, and administratively incompetent. Despite his ambitions toward the south and Ottoman Empire, Russia had not built its railroad network in that direction, and communications were poor. The bureaucracy was riddled with corruption and inefficiency and was unprepared for war. The Navy was weak and technologically backward; the Army, although very large, was good only for parades, suffered from colonels who pocketed their men's pay, poor morale, and was even more out of touch with the latest technology. The nation's leaders realized that reforms were urgently needed.

The early 19th century is the time when Russian literature becomes an independent and very striking phenomenon.

Westernizers favored imitating Western Europe while others renounced the West and called for a return of the traditions of the past. The latter path was championed by Slavophiles, who heaped scorn on the "decadent" West. The Slavophiles were opponents of bureaucracy and preferred the collectivism of the medieval Russian mir, or village community, to the individualism of the West. A forerunner of the movement was Pyotr Chaadayev. He exposed the cultural isolation of Russia, from the perspective of Western Europe, in his Philosophical Letters of 1831. He cast doubt on the greatness of the Russian past, and ridiculed Orthodoxy for failing to provide a sound spiritual basis for the Russian mind. He called on Russia to emulate Western Europe, especially in rational and logical thought, its progressive spirit, its leadership in science, and indeed its leadership on the path to freedom. Vissarion Belinsky and Alexander Herzen were prominent Westernizers.

Since the war against Napoleon, Russia had become deeply involved in the affairs of Europe, as part of the "Holy Alliance." The Holy Alliance was formed to serve as the "policeman of Europe." However, to maintain the alliance required large armies. Prussia, Austria, Britain and France (the other members of the alliance) lacked large armies and needed Russia to supply the required numbers, which fit the philosophy of Nicholas I. The Tsar sent his army into Hungary in 1849 at the request of the Austrian Empire and broke the revolt there, while preventing its spread to Russian Poland. The Tsar cracked down on any signs of internal unrest.

Russia expected that in exchange for supplying the troops to be the policeman of Europe, it should have a free hand in dealing with the decaying Ottoman Empire—the "sick man of Europe." In 1853, Russia invaded Ottoman-controlled areas leading to the Crimean War. Britain and France came to the rescue of the Ottomans. After a grueling war fought largely in Crimea, with very high death rates from disease, the allies won.

Historian Orlando Figes points to the long-term damage Russia suffered:

The demilitarization of the Black Sea was a major blow to Russia, which was no longer able to protect its vulnerable southern coastal frontier against the British or any other fleet.... The destruction of the Russian Black Sea Fleet, Sevastopol and other naval docks was a humiliation. No compulsory disarmament had ever been imposed on a great power previously.... The Allies did not really think that they were dealing with a European power in Russia. They regarded Russia as a semi-Asiatic state....In Russia itself, the Crimean defeat discredited the armed services and highlighted the need to modernize the countries defenses, not just in the strictly military sense, but also through the building of railways, industrialization, sound finances and so on....The image many Russians had built up of their country – the biggest, richest and most powerful in the world – had suddenly been shattered. Russia's backwardness had been exposed....The Crimean disaster had exposed the shortcomings of every institution in Russia – not just the corruption and incompetence of the military command, the technological backwardness of the army and navy, or the inadequate roads and lack of railways the accounted for the chronic problems of supply, but the poor condition and illiteracy of the serfs who made up the armed forces, the inability of the serf economy to sustain a state of war against industrial powers, and the failures of autocracy itself.

When Alexander II came to the throne in 1855, the demand for reform was widespread. The most pressing problem confronting the Government was serfdom. In 1859, there were 23 million serfs (out of a total population of 67 million). In anticipation of civil unrest that could ultimately foment a revolution, Alexander II chose to preemptively abolish serfdom with the emancipation reform in 1861. Emancipation brought a supply of free labor to the cities, stimulated industry, and the middle class grew in number and influence. The freed peasants had to buy land, allotted to them, from the landowners with the state assistance. The Government issued special bonds to the landowners for the land that they had lost, and collected a special tax from the peasants, called redemption payments, at a rate of 5% of the total cost of allotted land yearly. All the land turned over to the peasants was owned collectively by the mir, the village community, which divided the land among the peasants and supervised the various holdings.

Alexander was responsible for numerous reforms besides abolishing serfdom. He reorganized the judicial system, setting up elected local judges, abolishing capital punishment, promoting local self-government through the zemstvo system, imposing universal military service, ending some of the privileges of the nobility, and promoting the universities.

In foreign policy, he sold Alaska to the United States in 1867. He modernized the military command system. He sought peace, and joined with Germany and Austria in the League of the Three Emperors that stabilized the European situation. The Russian Empire expanded in Siberia and in the Caucasus and made gains at the expense of China. Faced with an uprising in Poland in 1863, he stripped that land of its separate Constitution and incorporated it directly into Russia. To counter the rise of a revolutionary and anarchistic movements, he sent thousands of dissidents into exile in Siberia and was proposing additional parliamentary reforms when he was assassinated in 1881.

In the late 1870s Russia and the Ottoman Empire again clashed in the Balkans. The Russo-Turkish War was popular among the Russian people, who supported the independence of their fellow Orthodox Slavs, the Serbs and the Bulgarians. Russia's victory in this war allowed a number of Balkan states to gain independence: Romania, Serbia, Montenegro. In addition, Bulgaria de facto became independent. However, the war increased tension with Austria-Hungary, which also had ambitions in the region. The Tsar was disappointed by the results of the Congress of Berlin in 1878, but abided by the agreement.

During this period Russia expanded its empire into Central Asia, conquering the khanates of Kokand, Bukhara, and Khiva, as well as the Trans-Caspian region. Russia's advance in Asia led to British fears that the Russians planned aggression against British India. Before 1815 London worried Napoleon would combine with Russia to do that in one mighty campaign. After 1815 London feared Russia alone would do it step by step. However historians report that the Russians never had any intention to move against India.

In the 1860s, a movement known as Nihilism developed in Russia. A term originally coined by Ivan Turgenev in his 1862 novel Fathers and Sons, Nihilists favoured the destruction of human institutions and laws, based on the assumption that they are artificial and corrupt. At its core, Russian nihilism was characterized by the belief that the world lacks comprehensible meaning, objective truth, or value. For some time, many Russian liberals had been dissatisfied by what they regarded as the empty discussions of the intelligentsia. The Nihilists questioned all old values and shocked the Russian establishment. They became involved in the cause of reform and became major political forces. Their path was facilitated by the previous actions of the Decembrists, who revolted in 1825, and the financial and political hardship caused by the Crimean War, which caused many Russians to lose faith in political institutions. Russian nihilists created the manifesto Catechism of a Revolutionary.

After the Nihilists failed to convert the aristocracy and landed gentry to the cause of reform, they turned to the peasants. Their campaign became known as the Narodnk ("Populist") movement. It was based on the belief that the common people had the wisdom and peaceful ability to lead the nation. As the Narodnik movement gained momentum, the government moved to extirpate it. In response to the growing reaction of the government, a radical branch of the Narodniks advocated and practiced terrorism. One after another, prominent officials were shot or killed by bombs. This represented the ascendancy of anarchism in Russia as a powerful revolutionary force. Finally, after several attempts, Alexander II was assassinated by anarchists in 1881, on the very day he had approved a proposal to call a representative assembly to consider new reforms in addition to the abolition of serfdom designed to ameliorate revolutionary demands.

The end of the 19th century and the beginning of the 20th is known as the Silver Age of Russian culture. The Silver Age was dominated by the artistic movements of Russian Symbolism, Acmeism, and Russian Futurism, many poetic schools flourished, including the Mystical Anarchism tendency within the Symbolist movement. The Russian avant-garde was a large, influential wave of modern art that flourished in Russian Empire and Soviet Union, approximately from 1890 to 1930—although some have placed its beginning as early as 1850 and its end as late as 1960.

Unlike his father, the new tsar Alexander III (1881–1894) was throughout his reign a staunch reactionary who revived the maxim of "Orthodoxy, Autocracy, and National Character". A committed Slavophile, Alexander III believed that Russia could be saved from chaos only by shutting itself off from the subversive influences of Western Europe. In his reign Russia concluded the union with republican France to contain the growing power of Germany, completed the conquest of Central Asia, and exacted important territorial and commercial concessions from China.

The tsar's most influential adviser was Konstantin Pobedonostsev, tutor to Alexander III and his son Nicholas, and procurator of the Holy Synod from 1880 to 1895. He taught his royal pupils to fear freedom of speech and press and to hate democracy, constitutions, and the parliamentary system. Under Pobedonostsev, revolutionaries were hunted down and a policy of Russification was carried out.

Alexander was succeeded by his son Nicholas II (1894–1918). The Industrial Revolution, which began to exert a significant influence in Russia, was meanwhile creating forces that would finally overthrow the tsar. Politically, these opposition forces organized into three competing parties: The liberal elements among the industrial capitalists and nobility, who wanted peaceful social reform and a constitutional monarchy, founded the Constitutional Democratic party or Kadets in 1905. Followers of the Narodnik tradition established the Socialist-Revolutionary Party or Esers in 1901, advocating the distribution of land among the peasants who worked it. A third radical group founded the Russian Social Democratic Labour Party or RSDLP in 1898; this party was the primary exponent of Marxism in Russia. Gathering their support from the radical intellectuals and the urban working class, they advocated complete social, economic and political revolution.

In 1903, the RSDLP split into two wings: the radical Bolsheviks, led by Vladimir Lenin, and the relatively moderate Mensheviks, led by Yuli Martov. The Mensheviks believed that Russian socialism would grow gradually and peacefully and that the tsar's regime should be succeeded by a democratic republic. The Bolsheviks advocated the formation of a small elite of professional revolutionaries, subject to strong party discipline, to act as the vanguard of the proletariat in order to seize power by force.

At the beginning of the 20th century, Russia continued its expansion in the Far East; Chinese Manchuria was in the zone of Russian interests. Russia took an active part in the intervention of the great powers in China to suppress the Boxer rebellion. During this war, Russia occupied Manchuria, which caused a clash of interests with Japan. In 1904, the Russo-Japanese War began, which ended extremely unfavourably for Russia.

The disastrous performance of the Russian armed forces in the Russo-Japanese War was a major blow to the Russian State and increased the potential for unrest.

In January 1905, an incident known as "Bloody Sunday" occurred when Father Gapon led an enormous crowd to the Winter Palace in Saint Petersburg to present a petition to the tsar. When the procession reached the palace, Cossacks opened fire, killing hundreds. The Russian masses were so aroused over the massacre that a general strike was declared demanding a democratic republic. This marked the beginning of the Russian Revolution of 1905. Soviets (councils of workers) appeared in most cities to direct revolutionary activity.

In October 1905, Nicholas reluctantly issued the October Manifesto, which conceded the creation of a national Duma (legislature) to be called without delay. The right to vote was extended, and no law was to go into force without confirmation by the Duma. The moderate groups were satisfied; but the socialists rejected the concessions as insufficient and tried to organize new strikes. By the end of 1905, there was disunity among the reformers, and the tsar's position was strengthened.

On 28 June 1914, Bosnian Serbs assassinated Archduke Franz Ferdinand of Austro-Hungary. Austro-Hungary issued an ultimatum to Serbia, which it considered a Russian client-state. Russia had no treaty obligation to Serbia, and most Russian leaders wanted to avoid war. But in that crisis they had the support of France, and believed that supporting Serbia was important for Russia's credibility and for its goal of a leadership role in the Balkans. Tsar Nicholas II mobilised Russian forces on 30 July 1914 to defend Serbia. Christopher Clark states: "The Russian general mobilisation [of 30 July] was one of the most momentous decisions of the July crisis". Germany responded with its own mobilisation and declaration of War on 1 August 1914. At the opening of hostilities, the Russians took the offensive against both Germany and Austria-Hungary.

The very large but poorly led and under-equipped Russian army fought tenaciously. Casualties were enormous. In the 1914 campaign, Russian forces defeated Austro-Hungarian forces in the Battle of Galicia. The success of the Russian army forced the German army to withdraw troops from the western front to the Russian front. However, victories in Poland by the Central Powers in the 1915 campaign, led to a major retreat of the Russian army. In 1916, the Russians again dealt a powerful blow to the Austrians during the Brusilov offensive.

By 1915, morale was worsening. Many recruits were sent to the front unarmed. Nevertheless, the Russian army fought on, and tied down large numbers of Germans and Austrians. When the homefront showed an occasional surge of patriotism, the tsar and his entourage failed to exploit it for military benefit. The Russian army neglected to rally the ethnic and religious minorities that were hostile to Austria, such as Poles. The tsar refused to cooperate with the national legislature, the Duma, and listened less to experts than to his wife, who was in thrall to her chief advisor, the holy man Grigori Rasputin. More than two million refugees fled. Repeated military failures and bureaucratic ineptitude soon turned large segments of the population against the government. The German and Ottoman fleets prevented Russia from importing urgently needed supplies through the Baltic and Black seas. By mid-1915 the impact of the war was demoralizing. Food and fuel were in short supply, casualties kept occurring, and inflation was mounting. Strikes increased among factory workers, and the peasants, who wanted land reforms, were restless. Meanwhile, elite distrust of the regime was deepened by reports that Rasputin was gaining influence; his assassination in late 1916 ended the scandal but did not restore the autocracy's prestige.