Which military order led the Northern Crusades against the Prussians?

The Teutonic Order led the principal Northern Crusades against the pagan Prussians. This German military-religious order was invited into the Baltic region during the 13th century after earlier Polish campaigns failed to subdue or convert the Old Prussians.

Duke Konrad I of Masovia appealed to the order in 1226, seeking help defending his lands and conquering Prussian territory. The Teutonic Knights established bases in Chełmno Land and began a sustained campaign in 1230. Over several decades, they built castles, defeated Prussian resistance, and created a powerful territorial state.

The order was not the only force involved. Polish princes, German nobles, crusading guests, and the Livonian branch of the order also participated. The Prussian Crusade was part of the wider Northern, or Baltic, Crusades, which extended across areas near modern Poland, Lithuania, Latvia, and Estonia.

The Knights Templar and Knights Hospitaller operated mainly in the eastern Mediterranean, although they sometimes participated in other campaigns. They were not the order that spearheaded the conquest of Prussia.