In 1368 Pomerania-Stolp ("Duchy of Słupsk") was split off from Pomerania-Wolgast due to the Partitions of the Duchy of Pomerania. The grandson of Polish King Casimir III the Great and his would-be successor Casimir IV became duke of Słupsk as a Polish vassal in 1374, after he failed to take the Polish throne. The succeeding dukes were also vassals of the Kings of Poland: Wartislaw VII paid homage in 1390 (to King Władysław II Jagiełło), Bogislaw VIII paid homage in 1410 (also to King Władysław II). Słupsk remained within Polish sphere of political influence until 1474. It became part of the Duchy of Pomerania in 1478.