In July 1660, Tsar Alexis I of Russia ordered Vasily Sheremetev to resume the sporadic Russo-Polish War and push the Poles west, taking Lviv and securing disputed Ukrainian territories for Russia. In September 1660, the commander of the Russian army, Sheremetev, acting on misleading information that greatly underestimated the numerical strength of the Polish army decided to seek out and destroy the Polish forces with what he believed would be overwhelming strength. Sheremetev's major tactical error was to advance relying on outdated and sparse intelligence reports, and without adequate scouting. He expected only a weak army of 10,000 under Great Crown HetmanStanisław "Rewera" Potocki and was unaware it was soon to be reinforced by about 12,000 men under Field Crown HetmanJerzy Sebastian Lubomirski who recently defeated a Russian army in Lithuania. The Polish commanders Hetmans Potocki and Lubomirski had much better intelligence and quickly became aware of Sheremetev's error. Polish historian Łossowski notes that "while Sheremetev's advanced blindly, the Polish hetmans knew almost everything about his army and moves". They decided to engage his forces before he could be reinforced by his Cossack allies. Part of the Cossacks were to stay with Sheremetev's corps, and another part, according to Sheremetev's plan were to intercept and defeat the 12,000 strong Tatars from the Crimean Khanate under nuradyn-sultan Safer Giray. However, Khmelnytsky failed to stop the Tatars and most of the Tatar forces slipped past him around middle of August. Further, the Cossack's leader, Yurii Khmelnytsky, was increasingly at odds with Sheremetev, and was in no hurry to execute Sheremetev's orders or stick to his plan. The Tatars met Potocki's forces on 1 September, and they in turn met with Lubomirski on 7 September, while Khmelnytsky was still far from Sheremetev's army. The combined Polish army numbered about 27,000. Sheremetev troops numbered 18,000.
Battle
The Russian army was surprised near Lyubar on 14 September and Sheremetev's vanguard was wiped out. Sheremetev, who had up until then failed to send out a single scouting party, suddenly realized what was to be an easy victory was a death trap and decided to take a defensive position in a fortified camp. The numerical superiority of the Polish forces, a lack of supplies and several minor defeats convinced him to break away on 26 September. At first the plan succeeded but the Polish forces caught up with the Russian army during its crossing of the Iber river and subsequently captured or destroyed a significant portion of the remaining Russian artillery and supplies.
Aftermath
The Polish forces caught up again with the Russians on 27 September near Chudniv. Sheremetev received a minor reinforcement by attaching Chudniv's garrison to his main army. However, with no further reinforcements, Sheremetev suffered a major defeat at the ensuing Battle of Chudniv.
