The Grand Duchy of Lithuania became a Swedish protectorate, the Polish–Lithuanian regular armies surrendered and the Polish king John II Casimir Vasa fled to the Habsburgs.

Exploiting the hurt religious feelings of the Roman Catholic population under Protestant occupation and organizing Polish–Lithuanian military leaders in the Tyszowce Confederation, John II Casimir Vasa managed to regain ground in 1656.

Charles X Gustav then granted Frederick William full sovereignty in the Duchy of Prussia in return for military aid, and in the Treaty of Radnot allied himself with the Transylvanian George II Rákóczi who invaded Poland–Lithuania from the southeast.

This triggered Frederick III of Denmark's invasion of the Swedish mainland in early 1657, in an attempt to settle old scores from the Torstenson War while Sweden was busy elsewhere.

After marching his army to the west and making a dangerous crossing of the frozen straits in the winter of 1657/58, he surprised the unprepared Frederick III on the Danish isles and forced him into surrender.

[8] In January 1654, the anti-Polish alliance of Pereiaslav was concluded between the rebellious Cossack Hetman Bohdan Khmelnytsky and Alexis of Russia, who was in control of a well-equipped army that was undergoing modernization.

Sweden, at that time an expansionist empire with an army designed to be maintained by the revenues of occupied territory, was conscious that a direct attack on her main adversary Russia could well result in a Dano-Polish–Russian alliance.

On the northern front, Prince Janusz Radziwiłł signed the Treaty of Kėdainiai with Sweden on 17 August 1655, placing the Grand Duchy of Lithuania under Swedish protection.

Though Radziwiłł had been negotiating with Sweden before, during his dispute with the Polish king, Kėdainiai provided a clause stipulating that the two parts of the Commonwealth, Poland and Lithuania, need not fight each other.

[17] In late October, Charles X Gustav headed northwards and left Wittenberg in Kraków with a mobile force of 3,000 Swedish and 2,000 Polish troops, and an additional number scattered in garrisons, to control the southern part of the Swedish-occupied commonwealth.

[18] In the north, the Royal Prussian nobles concluded a defensive alliance with the Electorate of Brandenburg on 12 November in the Treaty of Rinsk, permitting Brandenburgian garrisons.

[16] On 20 November a manifesto was issued in Opole (Oppeln) calling for public resistance and the return of John II Casimir,[19] and in December a peasant force took Nowy Sącz.

[24] In the same month, John II Casimir with the Lwów Oath proclaimed Virgin Mary queen of Poland, and promised to lift the burdens inflicted on the peasantry if he regained control.

[19] On 25 June 1656, Charles X Gustav signed an alliance with Brandenburg: the Treaty of Marienburg granted Greater Poland to Frederick William in return for military aid.

[24] Thereupon, Brandenburg actively participated in the war on the Swedish side, prompting John II Casimir Vasa to state that while his Tartars already had the Swedes for breakfast, he would now take Frederick William into custody, where neither sun nor moon would shine.

In August, Alexis' army took Livonian Kokenhausen (Koknese), laid siege to Riga and Dorpat (Tartu) and raided Estonia, Ingria and Kexholm.

[28] John II Casimir meanwhile took Bromberg (Bydgoszcz) and Konitz in Royal Prussia, and from 15 November 1656 until February 1657 stayed in Danzig, where a Swedish siege had to be lifted due to Dutch intervention, just 55 kilometers away from Charles X Gustav's quarters in Elbing.

[29] In the Treaty of Labiau on 20 November, Charles X Gustav of Sweden granted Frederick William of Brandenburg full sovereignty in the Duchy of Prussia in return for a more active participation in the war.

[29][31] In the Treaty of Radnot on 6 December, Charles X Gustav promised to accept George II Rákóczi of Transylvania as king of Poland and Grand Duke of Lithuania in return for his entrance into the war.

[29] Rákóczi entered the war in January 1657,[29][31] crossing into the commonwealth with a force of 25,000 Transylvanian-Wallachian-Moldavian men and 20,000 Cossacks who reinforced Kraków before they met with Charles X Gustav, who had led a Swedish-Brandenburgian army southwards.

[33] Brandenburg changed sides in return for Polish withdrawal of claims to Ducal Prussia, declaring Frederick William the sole sovereign in the Duchy with the treaties of Wehlau on 19 September and Bromberg on 6 November.

[31] The attack of Frederick III of Denmark in June 1657, aimed at regaining the territories lost in 1645, provided an opportunity for Charles X Gustav to abandon the unfortunate Polish–Lithuanian battlefields.

[34] Meanwhile, Polish forces led by general Stefan Czarniecki ravaged southern Swedish Pomerania, and destroyed and plundered Pasewalk, Gartz (Oder) and Penkun.

Although only 5,000 men made it across the belts, the Swedish attack was completely unexpected; Frederick III was compelled to surrender and signed the disadvantageous Treaty of Roskilde on 26 February 1658.

With Transylvania neutralized and Brandenburg defected, Charles X Gustav's position in the region was not strong enough to force his stated aim, the permanent gain of Royal Prussia.

[34] France was unwilling to intervene militarily, and Sweden could not afford to violate the Peace of Westphalia by attacking the Habsburg and Brandenburgian possessions in the Holy Roman Empire, which would likely have driven several Germans into the anti-Swedish alliance.

A combined force of 17,000 Austrians and 13,000 Brandenburgers[38] led by general Jean-Louis Raduit de Souches invaded Swedish Pomerania, took and burned Greifenhagen, took Wollin island and Damm, besieged Stettin and Greifswald without success, but took Demmin on 9 November.

The Swedish colonists were the preferred trading partners of the Susquehannock, who at that time were the most powerful indigenous group in the Susquehanna River valley and rivals to the Iroquois Confederacy further north.

[41][42] This effectively marked the end of New Sweden, but for a time the Swedish and Finnish settlers continued to enjoy local autonomy with their own militia, religion, court and lands.

Stuyvesant decreed that "like our neighbors of New England," the New Netherland colonists must now "concentrate themselves... in the form of towns, villages and hamlets, so that they may be the more effectually protected" against future attacks.