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.
Surprisingly, Casimir II was absent in the ceremony, and also began to refuse the payment of the customary tribute in successive periods (among his notorious absences was in 1428 at Łęczyca).
This situation could be maintained largely thanks to the support granted to Casimir II by the Lithuanian ruler Vytautas, who took up the prince on a campaign organized in 1428 against Veliky Novgorod.
The unexpected illness and death of his protector Vytautas forced Casimir II to change his position: in September 1430 at Sandomierz and almost four years after his brothers, he finally paid homage to the Polish King.
[1] In the following years, Casimir II was focused in the government of his domains, who were in the Polish-Lithuanian border; this obviously originated conflicts between the Polish (mainly from Lesser Poland) nobility and Švitrigaila's magnates.
The fights with varying degrees of success continued until 4 September 1437, where, in presence of Casimir II, the Polish nobles concluded at Lviv the final peace with Švitrigaila.