Küstrin (Polish: Kostrzyn), until 1928 also spelled Cüstrin, was a town in the former Prussian province of Brandenburg in Germany, situated on both sides of the Oder river. After World War II the Allies established a new border along the Oder-Neisse line according to the Potsdam Agreement, and the city with the Brandenburg Neumark region was divided between post-war Germany and the Republic of Poland. Küstrin became part of Poland and was renamed Kostrzyn nad Odrą.
The fortress of Kosterin, then held by Duke Władysław Odonic of Greater Poland, was first mentioned in a 1232 deed, at the time when it was enfeoffed to the Knights Templar. A Polish castellany since 1249, it passed to the Ascanian margraves of Brandenburg in 1261. Margrave Albert III vested the surrounding settlement with Magdeburg rights in 1300. To take advantage of its strategic location, from 1536 the fortress was largely rebuilt as the residence of the Hohenzollern margrave John of Brandenburg-Küstrin (Hans von Küstrin) and became one of the largest military structures in Germany under the rule of the "Great Elector" Frederick William during the 17th century.
Küstrin is significant as the site of the imprisonment of the young future King Frederick the Great by his father, Frederick William I, in September 1730. After his plans for fleeing Prussia with his friend Hans Hermann von Katte were discovered, Frederick was locked in Küstrin Tower, and ordered to watch the execution of his friend from his cell window. After his release from the prison, Frederick's father ordered him to stay on in Küstrin to learn the details of rural and city administration from the officials of the town.
In the late days of World War II, the fortress saw very heavy fighting between the Red Army and retreating Wehrmacht forces falling to Soviet forces on 11 March 1945. As a result, the Old Town section of Küstrin enclosed by its walls was completely destroyed and has not been rebuilt. The remaining German population was expelled.
The former Altstadt (Old Town) quarter was completely comprised by the fortification located on the peninsula between the Oder River and its Warta confluence. It originally included five bastions and cavaliers but no ravelin outworks. Surrounded by several earth walls, the structure was protected not only by the river courses but also by extended swamps in the east. The Margraviate of Brandenburg-Küstrin spent about 160,000 guilders for the erection until 1557.
In the following decade it was largely rebuilt as a brick construction according to plans by the Venetian architect Francesco Chiaramella de Gandino, who at the same time also worked on the Spandau Citadel. When Brandenburg-Küstrin fell back to the Hohenzollern main line upon the death of Margrave John in 1571, the construction of the walls continued under Elector John George of Brandenburg and his successors until 1619. The "Great Elector" Frederick William turned the fortress into barracks of the Brandenburg-Prussian Army in 1641.
The fortifications included the bastions König, Königin, Kronprinz, Kronprinzessin, Philipp and Brandenburg, linked by walls and surrounded by a moat. It also comprised the ravelins Albrecht, Christian-Ludwig and August-Wilhelm. Three gates led into the town: Berlin Gate in the north, Zorndorf Gate in the east, and Kietz Gate in the south. The walls encompassed the town centre with Küstrin Castle, St Mary's Church and the Renaissance town hall.
Information related to the divided town can be found in the following articles:
- Kostrzyn nad Odrą - town in Poland, with 19,952 inhabitants (2007). It contains within its boundaries most of the area of pre-1945 Küstrin,
- Küstriner Vorland - a municipality on the German side of the Oder river, with 2,953 inhabitants (2005). It contains within its borders the settlement Küstrin-Kietz, which was a western suburb of Küstrin before 1945,