Situation at Sandomierz 1656

So following on from the previous post, I decided to go with the chronologically first option, the battle of Sandomierz.

To give an understanding of the situation, at the beginning of 1656, The Polish Lithuanian Commonwealth was facing it's worst test, One which whilst it survived the ordeal, it never learnt from it, did the necessary reforms, and consequently, ended being partitioned between it's neighbours.

In 1655, Sweden decided to intervene in an exhausted Poland, wrought by years of Cossack wars and an ongoing war against Russia. Attacked from numerous directions, the Commonwealth collapsed, the King fled to Silesia and was the country basically completely conquered.

In the year is 1655, and all Poland is entirely occupied by it's enemies. Well not entirely, one small fortress held out against the invaders, Jasna Gora

Outnumbered 10:1, the Poles led by prior Kordecki, withstood the siege and bombardment, igniting a wave of resistance and guerrilla warfare across occupied Poland.

The Swedish garrisons at that time are reasonably well known, thanks to rusmilhist for the graphic. 

The Polish situation is slightly more difficult to ascertain, with widescale insurgent warfare happen across the land, and different mounted detachments under the various local leaders and the hetmans.

When the exiled Polish King returned to Polandm arriving on the 10 February 1656 in Lwów (Lviv) which, together with Gdańsk, was one of only two major cities of the Commonwealth not seized by any of Poland's enemies.
Soon Polish Army units began to concentrate in the area of Lwów, including militias from Red Ruthenia, Volhynia and Lublin, as well as forces under Potocki and Prince Lubomirski, together with the garrison of Kamieniec Podolski fortress. Charles Gustav, after finding out about the return of the Polish king, ordered his armies to concentrate in Łowicz.

The Swedes marched towards Lwów, reaching the Zamość Fortress on February 25. On March 1, realizing that without heavy guns it was impossible to capture the mighty stronghold, the Swedish army gave up the siege, and headed towards Bełżec. On March 3, Charles Gustav, whose units were harassed by Polish guerilla forces, decided to retreat. At the same time, guerilla warfare also broke out in Mazovia and Greater Poland, and Lithuanian units under the Grand Hetman of Lithuania Paweł Jan Sapieha began moving towards Red Ruthenia.

Army on the march, punishing partisans en route

On March 11, the Swedish army arrived at Jarosław, fighting its way across the San river. Charles Gustav sent some of his forces to capture Przemyśl, but on March 16 they returned to Jarosław without success. On March 22, the Swedish army set off northwards, along the San and Vistula rivers, back to Warsaw. They were followed by units of Stefan Czarniecki and Aleksander Koniecpolski, and during the retreat, Polish troops supporting the invaders changed sides, joining the forces of John Casimir. 

On March 30, the starving, cold and tired Swedish army of 5,000 stopped near Sandomierz, which was already in Polish hands. The Swedes camped among the forests of Sandomierz Forest near Gorzyce, near the confluence of the river San on the western side, and the Vistula on the eastern.

The battle at the confluence of the Vistula and San rivers near Sandomierz

Here they were quickly surrounded by approximately 23,000 Poles and Lithuanians.

Battle of Warka 1656

Historically, to help the besieged army, on March 27 Frederick VI left Warsaw with 2,500 reiters and dragoons, so John Casimir ordered the mounted units of Czarnecki and Lubomirski to face the margrave. Frederick's army was defeated on April 7 in the Battle of Warka. At Gorzyce, however, second-quality Polish forces remained, and the Swedish king managed to break out (April 5), and on April 13, Charles Gustav reached Warsaw.

This then is our starting point for our "imagination" campaign, or maybe better said deviation from history.