The Prussian uprisings were two major and three smaller uprisings by the Old Prussians, one of the Baltic tribes, against the Teutonic Knights that took place in the 13th century during the Prussian Crusade. The crusading military order, supported by the Popes and Christian Europe, sought to conquer and convert the pagan Prussians. In the first ten years of the crusade, five of the seven major Prussian clans fell under the control of the less numerous Teutonic Knights. However, the Prussians rose against their conquerors on five occasions. The first uprising was supported by Duke Swietopelk II, Duke of Pomerania. The Prussians were successful at first, reducing the Knights to only five of their strongest castles. The duke then suffered a series of military defeats and was eventually forced to make peace with the Teutonic Knights. With Duke Swietopelk's support for the Prussians broken, a prelate of Pope Innocent IV negotiated a peace treaty between the Prussians and the Knights. This treaty was never honored or enforced, especially after the Prussian victory in the Battle of Krücken at the end of 1249. The second uprising, known in historiography as "the great Prussian uprising", was prompted by the 1260 Battle of Durbe, the largest defeat suffered by the Teutonic Knights in the 13th century. This uprising was the longest, largest, and most threatening to the Teutonic Order, who again were reduced to five of their strongest castles. Reinforcements for the Knights were slow to arrive, despite repeated encouragements from Pope Urban IV, and the position of the Order looked set to worsen. Luckily for the Order, the Prussians lacked unity and a common strategy and reinforcements finally reached Prussia in around 1265. One by one, the Prussian clans surrendered and the uprising was ended in 1274. The later three lesser uprisings relied on foreign assistance and were suppressed within one or two years. The last uprising in 1295 effectively ended the Prussian Crusade, and Prussia became a Christian German-speaking territory, which assimilated native Prussians and a number of settlers from different German states. Background Although the Prussians repelled early incursions by the Order of Dobrzyń, they were outnumbered by attacks from Poland, Ruthenians in the southeast and the Teutonic Knights from the west. The Teutonic Order was called to the Culmerland in 1226 by Konrad I of Masovia, who started a number of attacks and crusades against the Prussians and later