In the Thirteen Years' War (1454-1466), the towns of Pomerelia and western Prussia rebelled against the Teutonic Knights and sought the assistance of King Casimir IV Jagiellon of Poland. In the Peace of Toruń in 1466, Pomerelia and western Prussia became the Polish province of Royal Prussia, which received several special rights, especially in Danzig (Gdańsk). Royal Prussia became part of the Polish-Lithuanian Commonwealth in 1569 and retained self-government by Prussian natives. Eastern Prussia, on the other hand, remained with the Teutonic Knights, who were reduced to vassals of Poland by the Peace of Toruń. This territory became the Duchy of Prussia in 1525 and removed the Polish suzerainty in 1657 Treaty of Wehlau. Most of Royal Prussia was annexed by the Kingdom of Prussia in the First Partition of Poland in 1772, and became the Province of West Prussia the following year, with the exception of Warmia which is located inside eastern Prussia and was joined to form the Province of East Prussia. In the Second Partition of Poland in 1793, the Hanseatic city of Danzig, no longer able to rely on its own strength, opted together with the Hanse city of Thorn to join the Kingdom of Prussia and thus West Prussia. Some of the areas of Greater Poland annexed in 1772 that formed the Netze District were added to West Prussia in 1793 as well. During the Napoleonic Wars in 1806, southern parts of West Prussia were moved to the Duchy of Warsaw. From 1824-1878 West Prussia was combined with East Prussia to form the Province of Prussia, after which they were reestablished as separate provinces. The region became part of the German Empire in 1871. After the Treaty of Versailles in 1919, most of West Prussia was granted to the Second Polish Republic, while small parts in the West and East of the former province remained in Weimar Germany. The western remainder formed Posen-West Prussia in 1922, while the eastern remainder became part of Regierungsbezirk West Prussia within East Prussia. In the Potsdam Conference of 1945 after World War II, all of former West Prussia was placed under the administration of Poland. The remaining German population of the region was expelled westward and replaced with Poles. In 1949, the refugees established the non-profit Territorial Association of West Prussia to represent West Prussians in the Federal Republic of Germany.
Note: Prussian provinces were subdivided into units called "Kreise" (singular "Kreis", abbreviated "Kr.", English circle), which were similar to large counties in Anglo-American terms. Cities would have their own "Stadtkreis" (English: municipal county) and the surrounding rural area would be named for the city, but referred to as a "Landkreis" (English: rural county).
Territories and Provinces of 
