Casimir I of Kuyavia
|Casimir I of Kuyavia|
Casimir I of Kuyavia
Constance of Wrocław
Euphrosyne of Opole
|Noble family||House of Piast|
|Father||Konrad I of Masovia|
|Mother||Agafia of Rus|
|Died||14 November 1267|
|Buried||Cathedral of Włocławek|
Casimir I of Kuyavia (Polish: Kazimierz I kujawski) (c. 1211 – 14 December 1267) was Prince of Kujawy, Mazovia and Wielkopolska, from 1233 until his death. He was the son of Konrad I of Masovia, King of Poland, and his wife Agafia of Rus.
Casimir received the Duchy of Kujawy on his father's death in 1233. In 1239 he received a dowry from his second wife Constance, daughter of Henry II the Pious. In subsequent years, his support of his father's turbulent politics brought him to the duchy of Gdańsk. Casimir's brother, Boleslaw, became Duke of Mazovia on the death of their father.
Casimir did not wish to create trouble with his brother Boleslaw over the inheritance. When Boleslaw died in 1248 he was childless, and all his possessions should have passed his brother Casimir. However, Boleslaw decided to leave his lands to their younger brother, Ziemowit.
Ziemovit allied with Daniel of Galicia against Casimir. As part of the alliance, Ziemovit married Daniel's daughter, Pereyaslava. In 1254, his brother made an alliance with the Teutons so that they would be defended against the advancing Baltic tribes. A coalition led by Boleslaw the Pious of Greater Poland in 1259 made Ziemovit give back some of the lands that were rightfully Casimir's. Some lands were given to Henry II the Pious.
In 1250, Casimir was trying to establish peaceful relations with his neighbors the Yotvingians. Unfortunately his peace plan was not supported by the Teutonic Order, who had the Pope on their side. After the plan failed, Casimir needed to deal with other land problems elsewhere in his territory. In order to secure the northern border of his territory, he appealed to the Knights Templar, who settled Łuków. It was not until 1263 that relations with the Teutonic Order returned to normal.
Meanwhile, Casimir faced more troubles. In 1258 Boleslaw the Pious made an alliance with Wartislaw III, Duke of Pomerania. They launched an attack against Casimir, claiming lands that had been given to him illegally by Henry II the Pious. The attack failed, but Boleslaw did not give up. The following year, he succeeded in bringing the powerful dukes Bolesław V the Chaste (Casimir's cousin), Siemovit and Daniel of Galicia) into his coalition against Casimir. Peace negotiations were difficult and require the coalition to launch a new attack against Casimir in 1261. Taking advantage his weakening father, Casimir's son Leszek II the Black made a claim on his inheritance. Casimir lost the Duchy of Sieradz, which he divided between his sons.
Casimir died in 1267 and was buried in the Cathedral of Włocławek.
Marriages and Children 
- Adelaide (before 7 April 1249-8 December 1291), nun
- Leszek II the Black (1240/42-30 September 1288), Duke of the Fragmentation of Poland
- Ziemomysł of Kuyavia (1241/45-29 October/24 December 1287), Duke of Kuyavia
- Władysław I the Elbow-high (1261-March 2, 1333), King of Poland (1320–1333)
- Casimir (1261/62-10 June 1294), killed while in battle in Lithuania
- Siemowit (1262/67-1309/14), Duke of Kuyavia-Brieg, married Anastasia of Galicia (daughter of Lev I of Galicia)
- Euphemia (d.18 March 1308), married Yuri I of Galicia