Zhmaylo Uprising The Zhmaylo Uprising ( ) was a Cossack rebellion headed by Marek Zhmaylo against the Polish - Lithuanian Commonwealth in 1625 . On 5 November Marek Zhmaylo was deprived of his title and Hetman Mykhailo Doroshenko was chosen to sign the Treaty of Kurukove , pledging allegiance to the Crown of the Kingdom of Poland . Background . In the late 16th century Poland introduced the institution of the Registered Cossacks , which granted some privileges to the militant Cossack people inhabiting territories of today Ukraine , then mostly controlled by Poland . Cossacks were allowed to serve in special units in the Polish military , but during the times of peace the Poles intended to reduce the number of Cossacks on the register and turn them into peasants . This happened again after the Polish - Ottoman War , in which aftermath the 40 , 000 mobilized Cossacks led then by Hetman Petro Konashevych - Sahaidachny were reduced to 5 , 000 . In response , the Cossacks began diplomatic endeavors with their Commonwealth neighbors , including the Tatars and the Muscovy . The Polish - Lithuanian government sent a special commission headed by Hetman Stanisław Koniecpolski , but two attempts to negotiate a truce failed . In September of 1625 Koniecpolski gathered an army to quell the unrest . Prelude . According to Leszek Podhorodecki , his forces numbered about 12 , 000 , with 30 artillery pieces ; and were composed of the regular army boosted by Registered Cossacks and forces of local nobility , both the pospolite ruszenie and some chorągiew units sponsored by the magnates . The Cossack leader Marek Zhmaylo had numerical superiority , gathering about 20 , 000 men under his banners . Uprising . On October 6 Koniecpolski left Bila Tserkva and headed south . Zhmaylo planned to draw the Polish army into the steppes , tire it out , cut its logistics , and only then engage it . In the meantime he retreated south , offering some resistance in the area of the village of Moszna and the river Cybulnik . On 24 October the Poles reached the town of Kryłów ( Крилів ) , where the Cossacks had created a fortified camp . There the Poles dispersed the Cossack cavalry and assaulted their tabor formation . The Cossacks held during the day , but attempted to withdraw in the night , a move which turned into a panicked retreat . Zhamaylo was able to restore order , helped by the fact that the Poles did not pursue the Cossacks till the following morning . At sunrise on 26 October the Poles caught up with the Cossacks near Lake Kurukove . The Polish cavalry charge got bogged down in the nearby swamps , and the Cossack counter - attack inflicted upon them serious casualties , turning the engagement into a siege of a new fortified camp . After several days the Cossacks removed Zhmaylo from command , and so negotiations began . Zhmaylo was replaced by Hetman Mykhailo Doroshenko who signed the Treaty of Kurukove with the Poles on 5 November 1625 ( Podhorodecki gives 6 November ) . Aftermath . In the end , despite no conclusive battle having been fought , Koniecpolski prevailed on the diplomatic front . The Cossacks were granted amnesty , but had to agree to register only 6 , 000 and stop raiding Ottoman Empire lands . However , this agreement would not be long lasting .