Polish forces under Grand Crown Hetman Mikołaj Firlej gathered near Koło and in January struck towards Pomesania towards Königsberg, laying siege to Marienwerder (Kwidzyn) and Preußisch Holland (Pasłęk). The siege was slow, however, since the Polish forces lacked artillery power. The Polish fleet began a blockade of Teutonic ports. The Knights, in the meantime, took the Warmian city of Braunsberg (Braniewo). The Polish army received artillery reinforcements in April and took Marienwerder and Preußisch Holland that month, but failed to retake Braunsberg.