The war with the Teutonic Knights in Kuyavia and the Battle of Płowce (1330–1332)
In 1330, the Teutonic Knights resumed hostilities. Crusaders successfully plundered cities in Kuyavia and Greater Poland: Radziejów, Bydgoszcz, and Nakło. Only by a daring crossing of the Vistula River by Władysław and an intrusion into Chełmno with the help of Lithuanians were the allies successful in besieging the castle of Kowalewo Pomorskie in September. Then, under the besieged castle of the Teutonic Knights in Lipienek, the king agreed to a seven-month truce on 18 October 1330. Unfortunately, during this trip, the alliance with the Duke of Lithuania was compromised as a result of a personal quarrel between Władysław and Gediminas.
In 1331, there was another armed expedition by the Teutonic Knights into Polish lands. This time, according to the action plan of the Order, the troops under the command of Dietrich von Altenburg were to coordinate with the expedition of King John of Bohemia. The two armies were to meet under the walls of Kalisz. In the middle of the year, Teutonic troops carrying out a reconnaissance effort entered Kuyavia and Greater Poland, including taking Pyzdry (where there was a skirmish with the Polish troops) and Gniezno. The main expedition was organized in September 1331. While the Knights went to meet at Kalisz as agreed, upon arrival, there were no Czech troops present. John of Bohemia had stopped in Silesia, where he effectively stopped the resistance of Bolko II of Świdnica and resolved the unsettled case of Głogów after the death of Duke Przemko II.
Unable to deliver a decisive blow to Władysław I Łokietek, the Knights decided to finally master Kuyavia. The night of 23–24 September saw the first major unresolved clash near Konin. Three days later, in the morning, Polish troops numbering about 5,000 and led personally by King Władysław and his son Prince Casimir encountered the rear guard of the Teutonic Knights near Radziejów. Taking advantage of the surprise, the Poles defeated the enemy unit and took Dietrich von Altenburg, the commander of the expedition, as a prisoner. In the afternoon, however, there was another clash near the village of Płowce. The battle was not settled because of the withdrawal of some Polish troops with Prince Casimir, and in the confusion, the Teutonic commander escaped from captivity. Though inconclusive, the Battle of Płowce was important psychologically for the Poles as it convinced them that the Knights were not insurmountable.
Soon after these events, peace negotiations were initiated in Inowrocław. However, this time it was not possible for Władysław to reach an agreement with the Teutonic Knights. In 1332, the Knights organized a big military expedition under the command of Otto von Luteberg. This time, the Polish forces were too thin to face the resistance of the Knights in the open field. On 20 April, after a nearly two-week siege, Brześć, the capital of Kuyavia, fell. Soon, the Teutonic Knights were also in the other main strongholds of the province – Inowrocław and Gniewkowo, the latter of which was destroyed on the orders of the prince of the land, Casimir III of Gniewkowo.
The loss of Kuyavia, which was his patrimony, was certainly very painful for Władysław, although in the same year, taking advantage of the death of Przemko II of Głogów, he took Zbąszyń in Greater Poland by the river Obra, which had been held by the dukes of Głogow.