Thorunium Primaria Prussiae Regal Urbis. . .

A decorative battle plan, showing the army of King Charles X Gustav of Sweden. Having routed the Polish armies where ever he met, them Charles X Gustav finally turned his attention back to his prime objective of taking control of the Baltic coasts of Royal Prussia with its Hanseatic port of Gdansk (Danzig), and of Ducal Prussia (a Polish fiefdom) with its port and Capital, Kaliningrad (Krolewiec, Konigsberg).
In previous months Swedish forces had successively captured most, if not all, of the major castles around Torun. Charles X Gustav, having gathered his available forces now marched on Torun. On the 24th November (4th December) 1656 the town capitulated without a fight and on 25th November (5th December) the king ceremoniously entered Torun. North is at the bottom.

Background: In 1648, the Peace of Westphalia brought to an end the 'Thirty Years’ War', and at the same time frustrated Sweden’s ambitions to control Baltic trade. Sweden was intent on gaining control of all of the Baltic trade (Dominium Maris Baltici) and the large customs duties deriving from it. All that was missing was control of the major ports on the southern coast of the Baltic or, alternatively, the Oresund, the gateway to the Baltic.
An early strike against Poland would isolate Prussia (east & west) forcing it to concede control of its ports, or at the very least pay Sweden a sizeable amount of its income for ‘protection’. In July 1655, Karl X Gustav, King of Sweden, declared war and invaded the Commonwealth of Poland and Lithuania, giving rise to what is known as the 2nd Northern War, and known in Poland as ‘The Deluge’.
The Commonwealth was already weakened by fighting on two fronts, In the Ukraine it was attempting to suppress a war of independence whilst in the east Russian forces were overrunning Lithuania and Belarus. By virtue of superior tactical use of infantry and artillery, within the space of 4 months Karl X Gustav had overrun the whole of the area of present day Poland and forced the Polish King, Jan II Casmir, to flee the Country.
All but a handful of the major strongholds gave up with barely any resistance, the notable exceptions being, Gdansk, Przemysl, Zamosc and Czestochowa.

Reference: Boden antique maps