It is known that they inherited a lifestyle that persisted there long before, such as those of the Turkic Cumans and the Circassian Kassaks (also spelled Kassogs). It is unlikely it could have happened before the 13th century, when the Mongols broke the power of the Cumans and other Turkic tribes on that territory. It is not clear when the Slavic people started settling in the lower reaches of major rivers such as the Don and the Dnieper. There are Cossack organizations in Russia, Kazakhstan, Ukraine and other countries. Special Cossack units exist in the Russian Military, while Cossacks also have a parallel civil administration and police duties in their home territories that have become an integral part of contemporary society. After the Collapse of the Soviet Union, the Cossack lifestyle and its ideas have made a return in Russia.

During the Second World War Cossacks fought for both the Soviet Union and for Nazi Germany, a choice which led to what has been called the ' Betrayal of Cossacks' by the Allied forces after the war, as the Soviet Union executed 'repatriated' Cossacks and again engaged in repressionary policies against their group. With the victory of the Red Army, the Cossack lands were subjected to famine, and suffered extensive repressions. The Don and Kuban Cossacks even formed short-lived independent states in their respective territories. This caused them to form a stereotypical portrayal of 19th century Russian Empire abroad and her government domestically.Дuring the Russian Civil War Cossack regions became centers for the Anti-Bolshevik White movement, a portion of whom would form the White emigration. In return they enjoyed vast social autonomy. By the end of the 18th century, Cossacks were transformed into a special social estate they served as border guards on national and internal ethnic borders (as was in the case in the Caucasus War) and regularly supplied men to conflicts such as the numerous Russo-Turkish Wars. In extreme cases whole Hosts could be dissolved, as was the fate of the Zaporozhian Sich in 1775. This resulted in rebellions led by Stenka Razin, Kondraty Bulavin and Yemelyan Pugachev. In the 18th century the Russian Empire's expansionist ambitions relied on ensuring the loyalty of Cossacks, which caused tension with their traditional independent lifestyle. The Don Cossack Host, allied with the Tsardom of Russia, began a systematic conquest and colonisation of lands to secure her borders on the Volga, the whole of Siberia, the Ural and the Terek Rivers. Afterwards, the Treaty of Pereyaslavl with Russia brought most of the Ukrainian Cossack state under Russian control for the next three hundred years. Initially a vassal of Poland-Lithuania, the increasing social and religious pressure from the Commonwealth caused them to proclaim an independent Cossack Hetmanate, initiating by a rebellion under Bohdan Khmelnytsky in the mid-17th century. The Dnieper Cossacks of Ukraine formed the Zaporozhian Sich centered around the fortified Dnieper islands. Other Cossack hosts were established later in the Southern Urals, Siberia and Caucasus. In the 16th century, the Don Cossacks established another cossack host in the Don River basin. Towards the end of the 15th century, Zaporozhian Cossacks had established a Cossack host in the ' wild field' of Ukraine around the Dnieper River. Their origin is a subject of scholarly dispute. Cossacks ( Ukrainian: РљРѕР·Р°РєРёМЃ, Kozaky Russian: РљР°Р·Р°РєРёМЃ, Kazaky Polish: Kozacy) were originally members of military communities in Ukraine and southern Russia.

Cossacks definition