A large Polish army had assembled, including detachments of the
Rid of the mixed blessing of the
Ossoliński and his more reasonable counterparts had managed to pour oil on the water once again, and Ukraine quietened down. It was not to last. In 1650 Chmielnicki accepted the overlordship of the Sultan, who named him vassal prince of Ukraine. Polish forces moved into Ukraine the following spring and in the threeday Battle of Beresteczko routed the Cossack army and its Tatar allies. A new peace was signed at Biala Cerkiew on 28 September 1651 annulling all previous Polish concessions, but while one Polish army set about pacifying the area, another which had gone to Moldavia to head off Chmielnicki’s Turkish allies was defeated and its remnants massacred at Batoh.
Władysław IV had been succeeded by his younger brother, Jan Kazimierz, a complex character with a chequered past. He was intelligent and resourceful, but he suffered from fits of depression and listlessness. His lack of charm did not help him gain the confidence of the szlachta, while many magnates felt an intense dislike for him. They also distrusted the Queen, Louise Marie de Gonzague, Duchesse de Nevers, Princess of Mantua.
Her grandfather, a friend and collaborator of Marie de Médicis, had come to Poland with Henri de Valois, and her father, the last Gonzaga Duke of Mantua, had also spent some time in Warsaw. She was brought up at the French court. In 1645, as a result of a rapprochement between Poland and France, she married Władysław IV, and after his death, his younger brother Jan Kazimierz. He was then forty, and she thirty-eight.
She and the bevy of young French ladies she had brought with her introduced French court culture into Poland, which, Cardinal Mazarin hoped, would facilitate his plan to bring the Commonwealth within the French orbit, and if possible place a Bourbon on its throne. From the outset they aroused Polish suspicions.
One faction among the magnates, including the Radziwiłł and Lubomirski families, believed in the necessity of the removal of Jan Kazimierz, and they began to plot accordingly. In the case of the Radziwiłł, it went further: the family had thought of themselves as quasi-royal for the last century, and their dream of assuming the throne of a separate Lithuania had grown into something of an obsession with Janusz Radziwiłł. Such attitudes helped destabilise the situation.
In 1654, Bohdan Chmielnicki, who had developed dynastic aspirations quite as extravagant as those of the Radziwiłł, negotiated the Treaty of Pereiaslav, placing himself under the protection of Muscovy in return for military assistance against the Commonwealth. Tsar Alexey began to style himself ‘Tsar of Great and Little Russia’. There were protests from some of the Cossacks, and the Metropolitan of Kiev announced that he for one was still a subject of the King of Poland. Alexey invaded Lithuania, defeated Janusz Radziwiłł and took Polotsk, Smolensk, Vitebsk and Mohilev, while the Cossacks reached Lublin. In the following spring he took Wilno, and titled himself ‘Grand Duke of Lithuania, Belorussia and Podolia’. Far from getting Lithuania for themselves, the Radziwiłł were now in imminent peril of becoming Muscovite subjects, and they reacted by appealing for help to the King of Sweden.