Complex sentence: While defending a castle under siege, Polish knights ambushed the Prussian army, and a knight named Dolega shot the hoof of the Prussian army commander's horse with his crossbow so well that the Prussian commander was thrown from it.
Split into simpler sentences: While defending a castle under siege, Polish knights ambushed the Prussian army. A knight named Dołęga shot the hoof of the Prussian army commander's horse with his crossbow so well that the Prussian commander was thrown from it.