 Complete the following phrase:  Uroš II , also known as Primislav Примислав or Prvoslav Првослав, was Serbian Grand Prince from 1145 to 1162, with brief interruptions as ruler by Desa, his brother. His rule was characterized by a period of power struggle, not only of the Serbian throne between the brothers but between the Byzantine Empire and Kingdom of Hungary, of which he took advantage. He had two brothers Desa and Beloš, and a sister Helena of Serbia, Queen of Hungary. Furthermore, Uroš II also had to contend with the 