The Thirteen Years' War, also called the War of the Cities, starts in 1454 as an uprising by Prussian cities and the local nobility with the goal of gaining independence from the Teutonic Knights.

The Prussian Confederation asks the Polish king for help and offers to incorporate Prussia into the Kingdom of Poland.

When the king agrees, war between Poland and the Teutonic Knights breaks out.

Dispute between Poland and the Teutonic Order over the control of Gdańsk Pomerania has lasted since the 1308 Teutonic takeover of Danzig (Gdańsk), when that territory had been taken from Poland and annexed by the Teutonic Order.

This result of this event is a series of Polish–Teutonic Wars throughout the fourteenth and fifteenth centuries.

In the fifteenth century, the towns of Prussia experience rapid economic growth, which is not, however, paralleled by an increase in their political influence.

The rule of the Teutonic Knights is seen as increasingly anachronistic—taxes (customs) and the system of grain licenses (every trader has to pay large fees for the privilege of trading grain) are hindering economic development in the province.

At the same time, the nobility wants a greater voice in the running of the country, and regard with envy neighboring Poland, where the nobility enjoys wider privileges.

The Knights are also accused of violating the few existing privileges of the nobility and the cities.

Craftsmen are discontented because of competition from so-called partacze, or artisans settled by the Knights near their castles.

Kashubians, Poles, Germans, and Prussians are slowly melting into one nation, and as national differences disappeared, the common goals of all the ethnic and social groups of Prussia became more prominent, and the Prussian estates leaned increasingly towards Poland.

Prussian knights had in 1397 founded a secret organization called the Eidechsenbund (English translation: Lizard Union), more or less against the Teutonic Knights, but that organization had failed as it was not supported by the urban population.

After the victory by the Polish and Lithuanian forces at Grünfelde near Tannenberg during the Polish-Lithuanian-Teutonic War from 1409 to 1411, the Prussian estates had eagerly pledged allegiance to King Władysław II Jagiełło (Jogaila) of Poland, but they had quickly returned to the order's rule after the Poles were unable to conquer Marienburg (Malbork).

A clause in the peace treaty stated that it was guaranteed by the Prussian states, which would gain the right to defy the Teutonic Order if it broke the treaty.

In the succeeding wars, the Prussian estates had opposes any conflict, and pushed the Grand Masters of the Teutonic Knights to make peace.

A group made up of individuals from the Prussian cities, nobility and clergy, had formed the Prussian Confederation on February 21, 1440 The main contributors were from the nobility of Culmerland (Chełmno Land), Thorn, Culm (Chełmno), and from the Hanseatic cities of Elbing (Elbląg) and Danzig.

Grand Master Paul von Rusdorf was seen to approve the existence of the confederacy, but his successor, Konrad von Erlichhausen, had opposed it.

His non-compromising policy is followed and intensified by Ludwig von Erlichshausen, who takes this office in 1449 or 1450.

The Prussian Confederation had in 1452 asked Frederick for mediation in their conflict with the Teutonic Order.

Disagreeing with the confederacy, Frederick had banned it and had ordered it to obey the Teutonic Order on December 5, 1453.

Faced with this situation, the Prussians send envoys to Poland—although the Prussian Confederation, under the influence of Thorn and the Pomeranian and Culmerland nobility, has already sought contact with the Poles.

They receive support, especially from Greater Poland and from the party of Queen Sophia of Halshany, mother of King Casimir IV Jagiellon of Poland.

The Bishop of Kraków, Zbigniew Oleśnicki, opposes this support and try to prevent war.

Casimir asks the Prussian Confederation for a more formal petition.

The Secret Council of the Prussian Confederation sends a formal act of disobedience to the Grand Master on February 14, 1454.

Two days later, the confederacy starts its rebellion and soon almost all Prussia, except for Marienburg, Stuhm (Sztum), and …

…Konitz (Chojnice), are free from Teutonic rule.

Most of the captured Ordensburg castles are immediately destroyed.

The confederacy sends an official delegation to Poland, headed by Johannes von Baysen, on February 10, 1454.

The delegates, in Kraków by February 20, have asked Casimir to bring Prussia into the Polish kingdom.

After negotiating the exact conditions of incorporation, the king agrees and delegates of the Prussian Confederation pledge allegiance to Casimir on March 6, 1454.

On the same day, the king agrees to all the conditions of the Prussian delegates—for instance, Thorn has demanded the destruction of the Polish city of Nieszawa—giving wide privileges to the Prussian cities and nobility.

Three days later, Johannes von Baysen is named as the first governor of Prussia.

Casimir marries Elisabeth of Austria, daughter of the late King of the Romans Albert II of Habsburg by his late wife Elisabeth of Bohemia, on March 10.

Her distant relative Frederick of Habsburg, who became Holy Roman Emperor in 1452, will reign as Frederick III until after Casimir's own death.

The marriage strengthens the ties between the house of Jagiello and the sovereigns of Hungary-Bohemia and puts Casimir at odds with the Holy Roman Emperor through internal Habsburg rivalry.

Elisabeth's brother is King Ladislaus the Posthumous.

Most of the Prussian estates, with the exception of the Bishopric of Warmia, pledge allegiance to their new ruler after April 15.

Poland sends the Grand Master a declaration of war, predated to February 22.

Both sides expect the war to end quickly.

Poland is in conflict with the Grand Duchy of Lithuania in 1454: although Casimir IV is Grand Duke of Lithuania as well as King of Poland, Lithuania will send no aid during the war to Poland, and aside from a few ineffective raids, will not participate during the conflict.

There is also the threat of attack by the Grand Duchy of Moscow and by the Ottoman Empire, which had sacked Constantinople in 1453.

Elsewhere, the international situation is quite good for Poland, as no outside states are likely to intervene.

The southern border of Poland is more or less secure because of the weakness of the Bohemia resulting from the Hussite Wars.

Bohemia’s internal problems render it unable to directly intervene in the conflict.

The Hanseatic League sympathizes with the Prussian cities but backs the Teutonic Knights because the order grants them additional privileges.

The Livonian Order, embroiled in problems with Denmark, is unable to help the Teutonic Knights in Prussia.

Because of the conflict between Sweden and Denmark, both sides will stay more or less neutral in the coming conflict.

France and England are too weakened after the Hundred Years' War; England is soon to be embroiled in a civil war, the Wars of the Roses.

The Duke of Burgundy, Flanders, and the Netherlands, Philip the Good, is more interested in creating an independent Kingdom of Burgundy.

Pope Nicholas V's primary concern is dealing with the Ottoman Turks.

The Teutonic army has around nine thousand cavalry and six thousand infantry under Bernard Szumborski.

The Polish army has sixteen thousand cavalry, a few thousand servants (who can be and usually are used in battles), a few hundred infantry, plus five hundred mercenaries and burghers from Gdańsk and two thousand mercenaries hired by the Prussian Confederacy, all under the command of King Casimir IV, advised by chancellor Jan Koniecpolski and Piotr from Szczekociny.

The Polish commanders are counting on the battle of Chojnice being won by the Polish heavy cavalry, not caring much about either artillery or infantry.

They had not thought that their opponents could change their traditional strategy, or that the Teutonic soldiers besieged in Chojnice could be anything more than spectators.

Bernard Szumborski, nonetheless, has planned a totally different kind of battle.

The Polish defeat is complete.

Three thousand bodies are left on the battlefield, three hundred knights are captured by the Teutons, including three main commanders: Mikolaj Szarlejski, Łukasz Górka, and Wojciech Kostka from Postupice.

The Teutonic Knights lose only around a hundred men.

Bernard Szumborski, is however, formally a Polish prisoner, since he had given a knight's word.

The battle proves that discipline and improved tactics, combined with a talented commander, can win against a larger, but more traditional army.

The Poles pay the price for ignoring terrain, infantry and artillery.

Capistrano has meanwhile found an ally in the Polish archbishop Zbigniev Olesniczki, who urges Casimir IV Jagellon, grand duke of Lithuania and king of Poland, to abolish the privileges that had been granted to the Jews in 1447.

In supporting Olesniczki's demand, Capistrano threatens the king, in case of resistance, with horrible sufferings in hell, and predicts great misfortune to the country.

The king at first refuses to comply; but when the Polish army is defeated in September, 1454, at Chojnice in the war with the Teutonic Knights (who are secretly assisted by the pope and the Polish Church), and the clergy announces that God has punished the country because of the king's negligence of the Church and for his protection of the Jews, Casimir yields and revokes the privileges which the latter had enjoyed.

This leads to persecutions of the Jews in many Polish towns.

Brandenburg had pawned the Neumark to the Teutonic Knights in 1402, and it had passed completely under their control in 1429, although the Order neglected the region as well.

After the Teutonic Knights' defeat in the Battle of Grunwald (Tannenberg) in 1410, the future Grand Master Michael Küchmeister von Sternberg had used the Neumark as a staging ground for an army of German and Hungarian mercenaries which he later used against the forces of King Władysław II Jagiełło of Poland.

This had allowed the Order to retain much of its territory in the First Peace of Thorn in 1411.

The Knights' mismanagement leads in 1454/1455 to their pawning of the Neumark back to Brandenburg, by now led by Elector Frederick II of the Hohenzollern dynasty (Treaties of Cölln and Mewe).