When the returned delegation informed John II Casimir of Khmelnytsky's new campaign the king called for all szlachta volunteer army, while sending the regular troops against cossacks to southern Volhynia. However, after obtaining an intelligence report of the superior cossack forces, the Polish troops retreated to Zbarazh to set a defense. The forces of Jeremi Wiśniowiecki reinforced the Zbarazh defenders while he took the lead of all Polish forces. Khmelnytsky besieged the city wearing down through series of random attacks and firing at it. The king while rushing to help Wiśniowiecki was ambushed with his newly gathered forces. Khmelnytsky leaving part of his army with Ivan Cherniata near Zbarazh moved together with İslâm III Giray to intercept the Polish reinforcements and block their way at a river crossing near Zboriv. Caught by some degree of surprise, John Casimir started negotiations with the Tatar's khan. With the khan on his side, they forced Khmelnytsky to start peace negotiations. Khmelnytsky signed the Treaty of Zboriv in August 1649, with a result somewhat less than the Cossack leader had anticipated from his campaign.