In 1648, the Cossacks living in what is today Ukraine, along with dissatisfied peasants and serfs, Orthodox clergy, and Ruthenian nobles, launched a successful rebellion against the Polish-Lithuanian Commonwealth. In the spring of the following year, the Cossacks were able to have their claims to three provinces recognized by the Polish crown and they established a new state – the Hetmanate.
Bohdan Chmielnicki created the standing Cossack army and administration. Polish magnates, who owned large tracts of land in the eastern territories, were generally not interested in creating a Commonwealth in which Cossacks would have equal footing with Poles and
Lithuanians. The fighting continued and by 1654 Chmielnicki signed a treaty with Moscow in the hopes of ending the conflict. Unfortunately, this did little to end the fighting with Poland. In the decades the foillowed, Cossacks supported a variety of factions who sought to control Ukraine – Poles, Muscovites and Ottomans.
The death of Chmielnicki was a great blow for the Cossacks as there was no other leader among them with such great authority and political vision. Conflict between the lower classes and the Cossack leadership grew in its intensity and some favored a stronger alliance with the Commonwealth. The election of Ivan Vyhovsky as Hetman brought about the Polish-Cossack Treaty of Hadziacz (1658) and consequently, a war with Moscow. Tatars supported Vyhovsky in the fight against Muscovites but there was no Polish involvement. Although the Cossacks destroyed the Muscovite army at Konotop (1659) Vyhovsky later resigned as Hetman and was replaced by Yuri Chmielnicki. Yuri lacked the brilliance of his father and came under the influence of his colonels who often conducted their own politics. This was one of the reasons for the defeat of Muscovite and Cossack forces by the Polish commanders Potocki and Lubomirski during the campaign of 1660 (Lyubar, Chudniv, Slobodyshche).
In the 1660s, the Commonwealth, Moscow and to a lesser degree the Tatars, all sought to control Ukraine. The area was decimated by decades of constant warfare and most parties were exhausted by fighting such long and futile wars. Much of the country was ravaged by Polish pacification operations and the forces of Czarniecki were particularly ruthless. As Moscow was unable to bring about peace with Poland, Hetman Petro Doroshenko strove to form a new alliance with the Ottomans. By the end of 1666 Doroshenko accepted the protection of Turkey and Crimea over Ukraine and from then on Poland had to face Cossack and Tatar forces in Ukraine.
Unable to gain control of all of Ukraine, Poland and Moscow divided the area into half. This arrangement was formalized with the Treaty of Andrusovo of 1667, in which Poland controlled the lands on the Right-bank of the Dnipro River, while Moscow took position of the Left-bank. While Hetman Doroshenko’s forces fought with the Ottomans and Tatars against the Poles in the 1672-1676, the Cossack military was not as strong as in the times of Chmielnicki. Cossack regiments were poorly trained, unmotivated, and were unable to conduct large offensive operations on their own. Over time, Cossack troops became little more than irregular troops who were used to support the ambitions of their particular foreign rulers.