sentences:  They point out that the historical information came from documents written by the Teutonic Knights and must have been ideologically charged to persuade the Pope to declare a crusade not only against the pagan Prussians but also against the Christian duke.Prussians besieged Teutonic castles and managed to capture all except for Elbing (Elbląg) and Balga in the eastern regions of Natangia, Barta and Warmia; Thorn (Toruń), Culm (Chełmno), and Rehden (Radzyń Chełmiński) in the western parts.In December 1242, the Knights were able to capture Sartowice, Swantopolk's castle on the banks of the Vistula.