Excerpts from Books and Wikipedia
"To his north lay the kingdom of Hungary, and to his west the territories of Serbia, Bosnia, and Croatia, all of them contested lands, all of them teetering uneasily between alliance and hostility. Hungary, settled by an alliance of Magyar tribes at the end of the ninth century, had by the end of the tenth reached a stable and Christianized existence . . . In 1161, the powerful and elderly Hungarian king Géza II died. His young and inexperienced heir was Stephen III, only fifteen when he inherited his father’s crown. . . . The Byzantine general Andronicus led the attack and won a staggering victory. Stephen III kept his throne but was forced to accept a peace that handed over control of Croatia, Dalmatia, and eventually Bosnia to Byzantium, which was exactly what Manuel had intended. . . . With Hungarian help, Stefan Nemanja deposed his brother and declared himself Grand Prince of all Serbia. . . . Stefan Nemanja now ruled a newly independent Serbia. His dynasty, the Nemanjic, would remain on the Serbian throne for two centuries. Manuel’s landgrab had extended the Byzantine borders; but it had also, unintentionally, set Serbia free." [Bauer: Renaissance World, p. 137-9] "Stefan Nemanja united Serbian territories, establishing the Medieval Serbian state [in 1166]. This marks the rise of Serbia which will dominate the Balkans for the next three hundred years. Allies of Serbia at this moment become the Hungarian Kingdom and the Republic of Venice." [Wikipedia: Timeline of Middle Ages]