The island of Khortytsya, in the Dnieper, was headquarters ( sich ) of the Zaporizhzhya Cossacks from the 16th to 18th cent. (The word Zaporizhzhya means "beyond the rapids," i.e., of the Dnieper.) For nearly three centuries the Zaporizhzhya Cossacks served as the rallying point for Ukrainian struggles against social, national, and religious oppression.
After the union of Poland and Lithuania in 1569, Ukraine came under Polish rule; but the Poles were too weak to defend it from frequent devastating Tatar raids. The need for self-defense led at the end of the 15th cent. to the rise of the Ukrainian Cossacks, who by the mid-16th cent. had formed a state, organized along republican lines and ruled by a hetman, along the lower and middle Dnieper. At its height it occupied most of S Ukraine except the Black Sea littoral, a possession of the Crimean khans. Although they formally recognized the sovereignty of the Polish kings, the Cossacks, for all practical purposes, enjoyed complete political independence.
By the end of the 16th cent., however, Poland sought fuller control over Ukraine and the Zaporizhzhya Cossacks. Persecution of the Ukrainian Orthodox Church after 1596 provoked repeated outbreaks among the Ukrainians, and the Cossacks, as staunch adherents of the Orthodox faith, participated actively in the rebellions. In 1648 the Zaporizhzhya Cossacks, led by Hetman Bohdan Chmielnicki, began a series of campaigns that eventually defeated the Poles and freed Ukraine from Polish domination. Chmielnicki's forces suffered defeat in 1651, however, and were forced at Bila Tserkva to accept a treaty unfavorable to Ukraine.
In 1654, Chmielnicki persuaded the Cossacks to transfer their allegiance to the Russian czars. By the Treaty of Andrusov in 1667, the left bank of the Dnieper and Kiev were ceded to Russia. The Russians proceeded to encroach upon Cossack privileges much as the Poles had, thus engendering revolts in what was left of the Zaporizhzhya territory. When Hetman Ivan Mazepa joined Charles XII of Sweden against Russia in the Northern War, he shared in the Swedish defeat at Poltava (1709). Many Zaporizhzhya Cossacks fled to the khanate of Crimea, but in 1734 they were allowed to return to their old territory and to establish a new Cossack headquarters.
Russia, however, continued to view the Cossacks with suspicion; and in 1775 the Russian army, on orders from Catherine II, destroyed the Zaporizhzhya camp, thus completely abolishing the last stronghold of Ukrainian independence. Most of the Zaporizhzhya Cossacks then moved to Turkish territory at the mouth of the Danube, where they founded a new community. In 1828–29, however, they returned to Ukraine and settled along the shores of the Sea of Azov.
When the Russians tried in the 19th cent. to settle them in the newly conquered N Caucasus, the Cossacks rebelled and were disbanded (1865). Those Zaporizhzhya Cossacks who had remained in Ukraine were allowed in 1787 to settle along the Black Sea shores between the Dnieper and Buh rivers; they became known as the Black Sea Cossacks. In 1792 they were resettled in the Kuban region and after 1860 became known as the Kuban Cossacks.