The town is situated at the confluence of the Bersa with the Vistula, which washes two sides of its walls.
"In front of the other face is a steep green eminence which the Poles had very strongly entrenched, and had erected upon it ten batteries of heavy cannon.

As the town could only be approached on this side the difficulties of the relieving force were enormous; but as the relief of the town was a necessity in order to enable Gustavus to carry out the campaign he intended, the king determined to make a desperate effort to effect it.
"He selected 3000 of his best Scottish infantry, among whom was Hepburn's own regiment, and 500 horse under Colonel Thurn.

When they were drawn up he gave them a short address on the desperate nature of the service they were about to perform, namely, to cut a passage over a strongly fortified hill defended by 30,000 men.

The column, commanded by Hepburn, started at dusk, and, unseen by the enemy, approached their position, and working round it began to ascend the hill by a narrow and winding path encumbered by rocks and stones, thick underwood, and overhanging trees.
"The difficulty for troops with heavy muskets, cartridges, breastplates, and helmets, to make their way up such a place was enormous, and the mountain side was so steep that they were frequently obliged to haul themselves up by the branches of the trees; nevertheless, they managed to make their way through the enemy's outposts unobserved, and reached the summit, where the ground was smooth and level.
"Here they fell at once upon the Poles, who were working busily at their trenches, and for a time gained a footing there; but a deadly fire of musketry with showers of arrows and stones, opened upon them from all points, compelled the Scots to recoil from the trenches, when they were instantly attacked by crowds of horsemen in mail shirts and steel caps.
Hepburn drew off his men till they reached a rock on the plateau, and here they made their stand, the musketeers occupying the rock, the pikemen forming in a wall around it.
"They had brought with them the portable chevaux-de-frise carried by the infantry in the Swedish service.

They fixed this along in front, and it aided the spearmen greatly in resisting the desperate charges of the Polish horsemen.