From The Gates of Europe: A History of Ukraine, by Serhii Plokhy (Basic Books, 2017), Kindle pp. 151-153:
Up to that point, developments resembled those of previous Cossack uprisings, but Khmelnytsky changed the familiar pattern. Before marching northward, capturing towns, and confronting the commonwealth army, he went south in search of allies. In a dramatic reversal of established steppe politics, he offered the Crimean khan his friendship and an opportunity. The cautious khan allowed his vassals, the Noghay Horde north of the Crimea, to join the Cossacks. For Khmelnytsky and the Cossack rebels, this was a major coup. While the popular image of the Cossack nowadays is a man on horseback, in the mid-seventeenth century most Cossacks were in fact infantrymen. They lacked a cavalry of their own because maintaining one was too expensive: only nobles could afford to keep a battle-ready horse, often more than one. Khmelnytsky’s new alliance with the Tatars, who fought on horseback, solved the cavalry problem. From then on, the Cossacks could not only take poorly fortified borderland towns or defend themselves in fortified camps but also confront the Polish army in the field.
It did not take long for the alliance to prove its worth. In May 1648, Cossack and Tatar forces defeated two Polish armies, one near the Zhovti Vody (Yellow Water) River near the northern approaches to the Zaporozhian Sich, the other near the town of Korsun in the middle Dnieper region. A key to Cossack success, apart from the participation of Noghay cavalry (close to 4,000 horsemen) in both battles, was the decision of some 6,000 registered Cossacks to switch sides, abandon their Polish masters and join the Khmelnytsky revolt. The Polish standing army was completely wiped out. Its two chief commanders, the Crown grand hetman and the Crown field hetman, as well as hundreds of officers, ended up in Tatar captivity.
While the Cossacks’ sudden success shocked the commonwealth, Khmelnytsky and his closest supporters could not believe their luck. The hetman did not know what move to make next. In June 1648, with the Polish armies gone and the commonwealth in disarray, Bohdan Khmelnytsky took something of a summer hiatus and retired to his native Chyhyryn to consider what to do. But the rebels refused to take any breaks. With the old registered Cossacks gathered near Bila Tserkva, a town south of Kyiv, the popular uprising began in earnest in the rest of Ukraine. Inspired by the news of Cossack victories, the peasants and the townspeople took matters into their own hands, attacking the estates of large landowners, harassing their retreating private armies, settling scores with nobles, and hunting down Catholic priests. But those who suffered most from the peasant revolt in the summer of 1648 were the Jews of Ukraine.
The first letters that Khmelnytsky sent to the authorities as the revolt began already mentioned Jewish leaseholders. The Cossack hetman complained of the “intolerable injustices” that the Cossacks were suffering at the hands of the royal officials, the colonels—Polish commanders of the registered Cossacks—and “even” the Jews. Khmelnytsky mentioned the Jews in passing, placing them in the third or even fourth echelon of Cossack enemies, but the rebels in Right-Bank Ukraine, where Jews began to suffer attack en masse in June 1648, had their own priorities. They assaulted and often killed Jews (especially men), leading to the destruction of entire communities, which they all but wiped from the map in the course of three summer months of 1648. We do not know the number of victims, as we do not know the number of Jews living in the region before the revolt, but most scholars estimate Jewish losses at 14,000 to 20,000 victims—a very high number, given the time and place. For all its rapid economic development, seventeenth-century Ukraine was relatively sparsely settled.
Twentieth-century Jewish and Ukrainian historians have placed considerable emphasis on the underlying social causes of anti-Jewish antagonism in Dnieper Ukraine of that period. Rivalry between Jewish and Christian merchants and artisans in the cities and towns, as well as the Jewish leaseholders’ role as middlemen between nobles and peasants, did indeed contribute to the violence unleashed by the Cossack revolt. But one should not lose sight of religious motives in the attacks on Ukrainian Jewry. Religion was essential to social identity on both sides of the Christian-Jewish divide. It was not for nothing that the best-known Jewish chronicler of the massacres, Nathan Hannover, called the attackers “Greeks,” referring to their Orthodox religion, not their nationality. Some rebels felt that they were on a religious mission to convert those Jews who had escaped the massacre. Forced conversion to Christianity saved the lives of many Jewish men. Some of them joined the Cossack ranks, while others returned to Judaism once the threat of annihilation was over.
Far Outliers 