The battle on the Ice happened in 1242 in the early years of the Northern crusades and while being very famous, it has nothing to do with the end of the Northern crusades.

The end of the Northern Crusades have more to do with these events;

• The Christianization of the Lithuanians

• The defeat of the Teutonic Order at Grunwald in 1410 and it's aftermath

• The Protestant Reformation

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Since 1230ad the Teutonic Order had conquered the pagan Prussians and established a Crusader State governed by the Order on the Baltic coast. The Order christianized and Germanized the local population while also resettling Germans into the territory which brought fast development of the territory. It wasn't easy and the Order had to put down several Rebellions harshly but the fighting pushed to the frontier.

Tensions rose between the Polish and the Teutonic Order as territorial disputes erupted into sporadic fighting/wars. But for the most part fighting in the 14th century was against the Lithuanians, a warrior pagan people. The fighting was extremely violent. Captured Teutonic Knights were often burned alive in their armor on top of their horses as sacrifices to pagan war gods.

The first sign of change happened in 1386ad when the polish had a succession crisis. Jogaila, Grand Duke of Lithuania converted to Christianity and married the Queen of Poland, joining Poland and Lithuania, the two main antagonists of the Teutonic Order, in personal union.

The Teutonic Order was still the preeminent power in the Baltic but victory in war was no longer guaranteed. It would take a prudent and pragmatic Grandmaster. Unfortunately for the Order, in 1407 they lost that Grandmaster, Konrad Von Jungingen, and he was replaced by Ulrich Von Juningen, his brother. Konrad warned against electing his brother before his death.

Ulrich was an impulsive and arrogant man. Through bad diplomacy, war was started in 1410 when the combined polish-Lithuanian army invaded the territory of the Teutonic Order. This resulted the disaster of the battle of Grunwald where nearly the entire leadership of the Teutonic Order was killed and the army destroyed.

The invasion was aided by a rebellion of the Nobility as they wanted a greater say in politics. The Order rallied at the great fortress in Marienburg and the fortress was besieged but not taken. The Treaty of Thorne was generous towards the Order as they had a greater standing in Europe but the seeds of their destruction was planted.

The Order's treasury was empty and Wars were becoming more expensive as the need for professional mercenaries outweighed need for Knights and the commanderies of the Order became increasingly independent and scornful of central authority.

The Order would pick another disastrous war in the 1450's known as the 13 years war, which saw the polish take western Prussia, including the capital at Marienburg and another noble uprising.

The Teutonic Order had lost its purpose with the christianization of the pagans and now it was losing its ability to remain as an independent state.

The final blow came in 1525 while Europe was splitting across Protestant and catholic lines. The final Grandmaster in Prussia would convert to lutherism along with most his men. Becoming Albert, Duke of Prussia under Polish Crown.

With the Teutonic State coming to an end, the last remnants of the Northern Crusades ended as well.

Source: Teutonic Order: Military history by William Urban