Editing Casimir IV Jagiellon (section)

==King of Poland==
[[File:Kazimerzjagiello.jpg|thumb|right|15th-century seal depicting Casimir IV on the throne.]]
In 1427, the [[Polish nobility]] initiated an anti-[[Jagiellonian]] opposition and attempted to have [[Władysław II Jagiełło]]'s sons [[Władysław III Jagiellon|Władysław III]] and Casimir IV Jagiellon declared illegitimate to the Polish throne as they, being sons of a [[Lithuanian nobility|Lithuanian noblewoman]] [[Sophia of Halshany]], had no blood link to the previous ruling Polish dynasty, the [[Piasts]], however Casimir's father ensured the succession for his sons.<ref name="Oxford">{{cite web |title=Jagiellonians Timeline |url=https://www.jagiellonians.com/jagiellonians-timeline |website=Jagiellonians.com |publisher=[[University of Oxford]] |access-date=20 April 2021 |language=en}}</ref>

Casimir succeeded his brother [[Władysław III of Poland|Władysław III]] (killed at the [[Battle of Varna]] in 1444) as King of Poland after a three-year interregnum on 25 June 1447. In 1454, he married [[Elizabeth of Austria (1436–1505)|Elisabeth of Austria]], daughter of King [[Albert II of Germany]] and [[Elizabeth of Luxembourg]],{{sfn|Nowakowska|2019|p=xi}} a descendant of King [[Casimir III of Poland]]. Her distant relative was [[Frederick III, Holy Roman Emperor]]. The marriage strengthened the ties between the house of Jagiellon and the sovereigns of Hungary-Bohemia and put Casimir at odds with the emperor through internal Habsburg rivalry.

That same year, Casimir was approached by the [[Prussian Confederation]] for aid against the [[Teutonic Order]], which he promised, by making the separatist [[Prussia (region)|Prussian]] regions a protectorate of the [[Kingdom of Poland (1385–1569)|Polish Kingdom]]. However, when the insurgent cities rebelled against the Order, it resisted and the [[Thirteen Years' War (1454–66)|Thirteen Years' War]] (1454–1466) ensued. After a long and expensive war, Casimir and the Prussian Confederation defeated the [[Teutonic Order]]. In the [[Second Peace of Thorn (1466)]], the Order recognized Polish sovereignty over the seceded western Prussian regions, [[Royal Prussia]], and the Polish crown's overlordship over the remaining [[Monastic State of the Teutonic Knights|Teutonic Monastic State]], transformed in 1525 into a duchy, [[Ducal Prussia]].

Elisabeth's only brother [[Ladislaus the Posthumous|Ladislaus, king of Bohemia and Hungary]], died in 1457, and after that Casimir and Elisabeth's dynastic interests were directed also towards her brother's kingdoms.

King Casimir IV died on 7 June 1492 in the [[Old Grodno Castle]] in the [[Grand Duchy of Lithuania]], which was in a [[Union of Krewo|personal union]] with [[Poland]].