Władysław I of Płock

For unknown reasons, in 1433 Władysław I quarreled with his brothers and strongly objected to their pro-Polish policy in the war against the Teutonic Order.

[1] At the end of the 1430s, Władysław I once again changed his policy towards Poland and approached to the first person in the Kingdom: Zbigniew Oleśnicki, Bishop of Kraków.

On 25 April, Władysław I and his nephew Bolesław IV of Warsaw agreed to support the Polish against the Hussite confederates led by Spytek of Melsztyn.

Using the chaos reigned in Lithuania after the death of Sigismund Kęstutaitis in 1440, they intervened and took the district of Podlachia, who once belonged to Janusz I of Warsaw (although only during his lifetime).

At that moment the Masovian rulers strongly supported Michael Žygimantaitis, the son of Sigismund Kęstutaitis, who was not only favorably accepted in the courts of Płock and Warsaw (who caused political agitation) but also married with Władysław I's youngest sister, Catherine.

Under the terms of the agreement Władysław I remained in the possession of Belz, and in return he stopped to support Michael Žygimantaitis in his fight for the Lithuanian throne.

Finally, in 1450 was made a complete agreement with the Kingdom of Poland, which was manifested when Władysław I, as a Polish vassal, send his troops to an expedition to Moldova.