Cossacks are a group of predominantly East Slavic people who originally are members of democratic, semi-military communities in Ukraine and Southern Russia.

They inhabit sparsely populated areas and islands in the lower Dnieper and Don basins, and play an important role in the historical development of both Ukraine and Russia.The origins of the first Cossacks are disputed.

Traditional historiography dates the emergence of Cossacks to the 14th to 15th centuries.

Towards the end of the 15th century, the Ukrainian Cossacks form the Zaporozhian Sich centered around the fortified Dnipro islands.

Initially a vassal of Poland-Lithuania, the increasing social and religious pressure from the Commonwealth causes them to proclaim an independent Cossack Hetmanate, initiated by a rebellion under Bohdan Khmelnytsky in the mid-17th century.

Afterwards, the Treaty of Pereyaslav brings most of the Ukrainian Cossack state under Russian control for the next 300 years.

The Don Cossack Host, which is established by the 16th century, allies itself with the Tsardom of Russia.

Together they begin a systematic conquest and colonization of lands in order to secure the borders on the Volga, the whole of Siberia, the Yaik and the Terek Rivers.

By the 18th century, Cossack hosts in the Russian Empire serve as buffer zones on her borders.

However, the expansionist ambitions of the empire rely on ensuring the loyalty of Cossacks, which causez tension with their traditional freedom and independence.

In the 17th and 18th centuries, this results in anti-imperial rebellions and wars led by Stenka Razin, Kondraty Bulavin and Yemelyan Pugachev.

In extreme cases, whole Hosts are dissolved, as is the fate of the Zaporozhian Sich in 1775.

By the end of the 18th century, Cossacks are transformed into a special social estate (Sosloviye); they serve as border guards on national and internal ethnic borders (as is the case in the Caucasus War) and regularly supply men to conflicts such as the numerous Russo-Turkish Wars.

In return, they enjoy vast social autonomy.

This causes them to form a stereotypical portrayal of 19th century Russian Empire abroad and her government domestically.During the Russian Civil War, Cossack regions become centers for the Anti-Bolshevik White movement, a portion of whom will form the White emigration.

The Don and Kuban Cossacks even form short-lived independent states, the Don Republic and the Kuban People's Republic, respectively.

With the victory of the Red Army, the Cossack lands are subjected to famine, and suffer extensive repression.

After the dissolution of the Soviet Union, the Cossack lifestyle and its ideas make a return in Russia.

In Russia's 2010 Population Census, Cossacks are recognized as an ethnicity.There are Cossack organizations in Russia, Kazakhstan, Ukraine, and USA.