Casimir II of Belz

Casimir II of Belz (pl: Kazimierz II bełski; 1401/03 - 15 September 1442), was a Polish prince member of the House of Piast from the Masovian branch. He was a Duke of Płock, Rawa Mazowiecka, Gostynin, Sochaczew, Belz, Płońsk, Zawkrze and Wizna during 1426-1434 jointly with his brothers, and after the division of the paternal inheritance between him and his brothers in 1434, sole ruler over Belz.

He was the third son of Siemowit IV, Duke of Masovia and Alexandra of Lithuania, daughter of Algirdas.

As a child, Casimir II was sent to Lithuania, an event that in the future would give him the support of the Grand Duke Vytautas. Also, he spend some time at the court of King Władysław II Jagiełło of Poland.

After 1420 Siemowit IV, due to his progressive blindness, gradually gave participation in the government to his adult sons. Casimir II and his older brother Siemowit V were formally named co-rulers. The first major challenge for Casimir II was the trip to Brest-Litovsk, where on 14 November 1425 he and his brother solemnly vowed to the crown his fidelity and acceptance in the recent controversy over the appointment of Stanisław z Pawłowic (former Chancellor of Siemowit IV) as Bishop of Płock.

Siemowit IV died on 21 January 1426 leaving his domains to his four sons: Siemowit V, Casimir II, Trojden II (d. 1427) and Władysław I (a fifth son, Alexander, followed a Church career). Not wanting to further weakened their positions and domains with subsequents divisions, they decided to co-rule all their paternal inheritance.

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