The Battle of Szkłów or battle of Shkloŭ or battle of Shklov on August 12, 1654 was one of the first battles of the Russo-Polish War (1654–67); it ended with a Polish victory contested, however, by other sources. A small Polish–Lithuanian force of about 6,000–7,000 under Great Lithuanian Hetman Janusz Radziwiłł surprised a numerically superior Russian force (of 40,000; some estimates speak of 70,000, but they are likely too high) under knyaz Yakov Cherkassky near Shklow (). The battle took place during a solar eclipse. The Russian forces, due to their surprise, were engaged by the Poles unprepared and in smaller portions, which were defeated in turn. Eventually the Poles forced the entire Russian army to retreat; the losses are estimated at about 700 for the Poles and 7,000 for the Russians (although they may be overestimated for both sides). Prelude The conflict was triggered by the Khmelnytsky Rebellion of Ukrainian Cossacks against the Polish–Lithuanian Commonwealth. The Cossack leader, Bohdan Khmelnytsky, derived his main foreign support from Alexis of Russia and promised his allegiance in recompense. Although the Zemsky Sobor of 1651 was poised to accept the Cossacks into the Moscow sphere of influence and to enter the war against Poland on their side, the Tsar waited until 1653, when a new popular assembly eventually authorized the unification of Ukraine with Tsardom of Russia. After the Cossacks ratified this agreement at the Pereyaslav Rada the Russo-Polish War became inevitable. In July 1654 the Russian army of 40,000 (nominally under the Tsar, but in fact commanded by Princes Yakov Cherkassky, Nikita Odoevsky and Andrey Khovansky) captured the border forts of Bely and Dorogobuzh and laid siege to Smolensk. The Russian position at Smolensk was endangered as long as Great Lithuanian Hetman, Prince Janusz Radziwiłł with 10,000 men held Orsha, slightly to the west. Cherkassky decided to seek out Radziwiłł and defeat him. The Russian army which besieged Smolensk didn't risk a storm of the city as long as a Lithuanian army of Janusz Radziwiłł operated in the east. It was decided to send an army towards Radziwiłł which was supposed to block him. The army led by Yakov Cherkassky took Orsha and faced the Lithuanian forces. Battle The battle is described quite differently in Polish and Russian accounts, each side claiming it as their victory. According to Polish account, Radziwiłł became aware that the Russian army would be crossing the Dniepr