Battle of Ujście The Battle of Ujście was fought on July 24 – 25 , 1655 between forces of the Polish - Lithuanian Commonwealth commanded by Krzysztof Opaliński and Andrzej Grudziński on one side , and on the other Swedish forces commanded by Arvid Wittenberg . Krzysztof Opaliński and Bogusław Leszczyński , dissatisfied with policies of Jan Kazimierz , decided to become Swedish allies together with the pospolite ruszenie ( " Levée en masse " ) of Greater Poland to Charles X Gustav of Sweden . Introduction . In the summer of 1655 , the Swedish Empire invaded the Polish - Lithuanian Commonwealth , entering Poland - Lithuania from Swedish Pomerania and Swedish Livonia . On July 5 , 1655 , Arvid Wittenberg concentrated his forces near Stettin , and marched towards the Polish border . He was faced by the Levée en masse from the province of Greater Poland . Polish forces were made of local szlachta , which had not experienced any major military conflicts , and was unprepared to fight professional Swedish army , which was largely based on mercenaries , veterans of the Thirty Years ' War . Wittenberg ’ s army of 17 , 000 crossed Polish border near Czaplinek , on July 21 . Polish forces , concentrated near Ujscie consisted of 13 , 000 nobility , plus 1 , 400 chosen infantry . The Poles were supposed to be commanded by Boguslaw Leszczynski , who feigned illness and left to Breslau . In the absence of Leszczynski , the command was shared by Voivode of Poznan Krzysztof Opalinski , and Voivode of Kalisz , Andrzej Karol Grudzinski . Their task was to defend the Notec river crossings before the arrival of main forces , commanded by King Jan Kazimierz . The Battle . On July 24 , Wittenberg ’ s army reached Ujscie , urging Polish forces to capitulate . After the refusal , Wittenberg placed his artillery opposite Polish trenches , and began a barrage . For five hours , the chosen infantry defended bridges over the Notec and the Gwda rivers , retreating after running out of ammunition . At the same time , Swedish cavalry unit managed to capture a bridge near Dziembowo . Facing encirclement , Polish leaders decided to negotiate . Furthermore , panic broke out in Polish camp . Capitulation . On the next day , July 25 , Polish leaders signed capitulation , pledging allegiance to the Swedish king . Among the dignitaries who signed the act were such names , as Voivode of Poznan Krzysztof Opalinski , Voivode of Kalisz Andrzej Karol Grudzinski , Castellan of Międzyrzecz Pawel Gembicki , Castellan of Krzywin Maksymilian Miaskowski and Andrzej Slupecki . After the pact , Greater Poland ’ s nobility , which stayed at the Ujście camp , was invited by the Swedes to a feast . According to the document signed by the Poles , Charles X Gustav was given complete control of the two Greater Poland ’ s voivodeships , together with all church and royal properties , royal towns ( Poznań , Kalisz , Kościan , Międzyrzecz ) , and royal castles . The nobility was granted guarantee of its freedoms ( see Golden Liberty ) , and only Poles were to be nominated to the posts of civil servants . Consequences . The capitulation , which took place after a short battle , opened to the Swedes the way towards defenseless central Poland . Wittenberg however headed southwest , to Poznań , which he captured without fighting on July 31 . In early August he camped near Sroda Wielkopolska , awaiting the arrival of the army commanded by Charles Gustav . News of the capitulation reached Warsaw on July 31 . Shaken and desperate Polish king Jan Kazimierz Waza urged Austrian Emperor for help . Furthermore , on August 2 Jan Kazimierz expressed his willingness to hand the Polish crown over to Emperor Ferdinand III . The Battle of Ujscie is now regarded in Poland as a symbol of treason . Politician and publicist Piotr Naimski wrote in his essay “ Zaczęło się pod Ujściem ” ( “ It all began at Ujście ” ) that the source of the national weakness of the Poles lies at Ujscie : “ Before 1655 , all cases of treason were severely punished . After the meeting with Swedes , where a group act of treason took place , its participants were not condemned . Furthermore , they were later allowed to return to Poland , and to participate in public life ( . . . ) It was after Ujscie that collaboration and treason emerged as one of possible choices in the so - called “ decent families ” . It was not only the Swedish invasion in itself that undermined Polish statehood . It also was the weed of treason , which was allowed to take root and with which we still struggle ” . Polish historian Józef Szujski described the events at Ujście in the following way : “ The year 1655 brought a shameful renunciation of the Polish crown by Jan Kazimierz . This was a symbolic confirmation of the fact that the idea of a state , the idea of a monarchy , the allegiance to the government , was deeply undermined . The tragic cycle of invasions began with capitulation and treason of Greater Poland ’ s levee en masse . Despite the convenient , defensive position of the Ujscie camp , despite numerical superiority , the nobility gathered at Ujscie decided to negotiate with Wittemberg and traitor Hieronim Radziejowski , accepting the protectorate of Charles Gustav " .