At that time, the late 1408, Stefan protested against his younger brother Vuk. The reason for his dissatisfaction was that Stefan did not want to share throne with him and give him part of the state administration. In turn, Vuk was probably disappointed to Stefan's connecting with Sigmund I and the West. He therefore went to Süleyman and asked him for military assistance against Stefan. In return, he promised to recognize his sovereignty, if he receives his own state and if Branković and his brothers joined him.