You are wrong. It was an actual alliance between Christians and Pagans to defeat a Pagan Slavic tribe not the Pagan Old Prussian Balts.
Okay....maybe you will believe other sources:
In 1230, following the Golden Bull of Rimini, Grand Master Hermann von Salza and Duke Konrad I of Masovia launched the Prussian Crusade, a joint invasion of Prussia to Christianise the Baltic Old Prussians. The Order then created the independent Monastic State of the Teutonic Knights in the conquered territory, and subsequently conquered Courland, Livonia, and Estonia. The Dukes of Poland accused the Order of holding lands rightfully theirs.
During an attack on Prussia in 1233, over 21,000 crusaders took part, of which the burggrave of Magdeburg brought 5,000 warriors, Duke Henry of Silesia 3,000, Duke Konrad of Masovia 4,000 [...]
It was Christians against Pagans...no christian/pagan alliance!