Stefan Dragutin, the eldest son of king…
1276 CE
Stefan Dragutin, the eldest son of king Stephen Uroš I of Serbia by Helen of Anjou, had married Catherine, daughter of Hungarian king Stephen V. He is the leading Hungarophile in Serbian politics, and because of this he comes in conflict with his father, from whom he then usurps the throne in 1276 with help of Hungary, after a clash with his forces at Battle of Gacko.
He begins to attack the restored East Roman Empire but has no success.