communities, resembling pirates and pioneers of the New World. In 1648, the peasants of Ukraine joined the Zaporozhian Cossacks in rebellion against Polish-Lithuanian Commonwealth during the Khmelnytsky Uprising, because of the social and religious oppression they suffered under Polish rule. In 1654 the Ukrainian leader, Bohdan Khmelnytsky, offered to place Ukraine under the protection of the Russian Tsar, Aleksey I. Aleksey's acceptance of this offer led to a protracted war between Poland and Russia. Finally, Ukraine was split along the river Dnieper, leaving the western part (or Right-bank Ukraine) under Polish rule and eastern part (Left-bank Ukraine and Kiev) under Russian. Soon after that, in 1670–71 the Don Cossacks led by Stenka Razin initiated a major Cossack and peasant uprising in the Volga region, but the Tsar's troops were successful in defeating
In the east, the rapid Russian exploration and colonisation of the huge territories of Siberia was led mostly by Cossacks hunting for valuable furs and ivory. Russian explorers pushed eastward primarily along the Siberian river routes, and by the mid-17th century there were Russian settlements in the Eastern Siberia, on the Chukchi Peninsula, along the Amur River, and on the Pacific coast. In 1648 the Bering Strait between Asia and North America was passed for the first time by the expedition of Fedot Popov and Semyon Dezhnev.
Under Peter I (Peter the Great), Russia was proclaimed an Empire in 1721 and became recognized as a world power. Ruling from 1682 to 1725, Peter defeated Sweden in the Great Northern War, forcing it to cede West Karelia and Ingria (two regions lost by Russia in the Time of Troubles), as well as Estland and Livland, securing Russia's access to the sea and sea trade. On the Baltic Sea Peter founded a new capital called Saint Petersburg, later known as Russia's Window to Europe. Peter's reforms brought considerable Western European cultural influences to Russia.
The reign of Peter I's daughter Elisabeth in 1741–1762 saw Russia's participation in the Seven Years War (1756–1763), sometimes called the first actual World War. During this conflict Russia was able to annex Eastern Prussia for a while, and even take Berlin once, however upon Elisabeth's death all these conquests were returned to Kingdom of Prussia
A birch forest in Siberia, Novosibirsk Oblast. Birch is a national tree of Russia.