However, it initiated numerous campaigns against its Christian neighbors, the Kingdom of Poland, the Grand Duchy of Lithuania, and the Novgorod Republic (after assimilating the Livonian Order).

The Teutonic Knights had a strong economic base, and could hire mercenaries from throughout Europe to augment their feudal levies, and became a naval power in the Baltic Sea.

By the late fourteenth century, the Knights became the strong-arm of German Imperial policy in the Baltic Region, imposing the Holy Roman Emperor's will upon both the non-Christianized peoples and subjugated Poles, Pomeranians, Livonians, Lithuanies, and residents of such mercantile cities as Danzig.

Within the decade, the future of the Order, and its incessant and barbarous actions with Poland and the Latvian, Lithuanian, and Livonian peasants,[5] was debated at the Council of Constance (1415–1416).

Two days later the confederacy started its rebellion and soon almost all Prussia, except for Marienburg, Stuhm (Sztum), and Konitz (Chojnice), were free from Teutonic rule.

[9] In early 1454, the Grand Master Ludwig von Erlichshausen took refuge in Marienburg, as a defense against the incursion of the Prussian Confederacy and its ally, the King of Poland.

To prevent the town from being cut off from communication, the knights made constant sorties and at least once broke the lines of the besiegers, capturing the guns, supply trains, and about 300 prisoners.

Despite initial problems, the Poles, who had received orders to follow up on the siege with vigor, continued in their efforts, effectively regrouping outside the city walls, and repulsing the small number of knights who made regular forays against them.

The Prussian troops, upon being told that their former masters had, with a mere handful of men, overthrown and routed the most powerful army in the region, worried they would soon follow in this fate.

[Note 1] The outbreak of an epidemic made matters worse; the priests told the Prussians that the illness was retribution for their disobedience to the Order.

[14] Within the year of the collapse of the sieges at Marienburg and Konitz, Casimir brought 150,000 men across the Vistula river and continued with a stronger (and successful) assault on the Order.