When Rumelian beylerbey and vizier Hadım Şehabeddin was defeated by John Hunyadi in 1442, he was replaced by Kasım Pasha at both positions.
[1] At the beginning of the Crusade of Varna John Hunyadi crossed the Danube and rushed south along the river Morava to attack forces of Kasım Pasha before he could mobilize his complete army.
[2] The cavalry forces of 12,000 commanded by Kasım Pasha were defeated near Aleksinac during the Battle of Niš in 1443.
[3][4] After an Ottoman defeat, the retreating forces of Kasım Pasha and Turahan Bey burned all villages between Niš and Sofia.
[6] Kasım Pasha commanded Ottoman forces that chased Christian army after the Battle of Zlatica held at the end of 1443.