Battle of Shklow ( 1654 ) 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 – 1667 ) ; it ended with a Polish victory . A small Polish - Lithuanian force of about 6 , 000 – 7 , 000 under Great Lithuanian Hetman Janusz Radziwiłł surprised a numerically superior Russia n force ( of 40 , 000 ; some estimates speak of about 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 river ; he had about 2 , 000 cavalry and some few thousands of infantry ( including the more mobile dragoons ; about 4 , 000 – 5 , 000 ) . Around 2 pm he was informed that the Russians were close and their first units had started to cross the river ; his main force also had the benefit of not being seen by the Russians . In the meantime , a solar eclipse began , creating confusion . Polish cavalry , including the Winged Hussars , launched repeated attacks on the Russian forces that had crossed the river , pushing them back . Russian attempts to cross the river were repeatedly forced back into the water , and attempts to outflank the Polish forces were stopped by the infantry , which took positions along the river and fired at the Russian forces which attempted to cross the river elsewhere . After five or so hours , both sides attempted a major push , and the Poles again were victorious ; the Russians , having sustained much higher casualties than the Poles ( about 7 , 000 compared to 700 ) , were demoralized and abandoned attempts to cross the river . The same source claims that among their dead was knyaz Yuri Baryatinsky which is obviously wrong . Russian sources give a different account . According to them , after having discovered the Lithuanian army , a detachment under Prince Yuri Baryatinsky was involved in the fighting with the Lithuanians while the voivode s of the main army led by Cherkassky sent Baryatinski their cavalry as reinforcement . The rest of the army which consisted of infantry , reiter s and supply wagons , also began to move to the battle site . Baryatinsky conducted several attacks on the army of the Great Hetman . Having learned about the approach of the main army of Cherkassky , Radziwiłł decided to retreat . Cherkassky didn ' t pursue the Lithuanians . Significance . Szkłów was the last ( if dubious ) victory of Janusz Radziwiłł , a powerful and ambitious magnate . Cherkassky retreated temporarily but only to merge with another Russian army under Aleksey Trubetskoy ; later that month Radziwiłł would face defeat at the battle of Szepielewicze ( Shepeleviche ) . That battle would mark Russian victory in Lithuania . Shklov was taken by the Russians in September 1654 . The besieged Polish - Lithuanian garrison of Smolensk found itself in an isolated situation and lost its hopes to hold out until reinforcements could arrive . This forced the garrison to surrender ( see Siege of Smolensk ( 1654 ) ) . A few months later Janusz Radziwiłł would defect from Polish side to that of the invading Swedes , and would eventually die fighting for them , remembered as a traitor in Polish historiography .