https://en.wikipedia.org/wiki/Polish%E2%80%93Lithuanian%E2%80%93Teutonic_War

War began with a Teutonic invasion of Poland in August 1409. As neither side was ready for a full-scale war, Wenceslaus IV of Bohemia brokered a nine-month truce. After the truce expired in June 1410, the military-religious monks were decisively defeated in the Battle of Grunwald, one of the largest battles in medieval Europe. Most of the Teutonic leadership was killed or taken prisoner. The war shifted the balance of power in Central Europe and marked the rise of the Polish–Lithuanian union as the dominant power in the region.

https://en.wikipedia.org/wiki/Battle_of_Grunwald

>>13471586

>the knights murdered a number of citizens within the city and took it as their own

>>13471624

Soon after the take-over, on 19 June 1310, the Teutonic Knights faced charges that they had committed a massacre in a bull issued by pope Clement V:

"Latest news were brought to my attention, that officials and brethren of the aforementioned Teutonic order have hostilely intruded the lands of Our beloved son Wladislaw, duke of Cracow and Sandomierz, and in the town of Gdańsk killed more than ten thousand people with the sword, inflicting death on whining infants in cradles whom even the enemy of faith would have spared."

>>13471724

>https://en.wikipedia.org/wiki/Free_City_of_Danzig

https://en.wikipedia.org/wiki/Polish_Corridor

The Danzig / Gdańsk Corridor was a territory located in the region of Pomerelia which provided the Second Republic of Poland (1920–1939) with access to the Baltic Sea, thus dividing the bulk of Germany (Weimar Republic) from the province of East Prussia. The Free City of Danzig was separate from both Poland and Germany. A similar territory, also occasionally referred to as a corridor, had been connected to the Polish Crown as part of Royal Prussia during the period 1466–1772.