Hungarian-Serbian AllianceDubrovnik, Croatia
After the death of Emperor Manuel on September 24, 1180, the Hungarian king Bela III considered that he had no more obligations to Byzantium. The following 1181, he launched an offensive against Byzantium and conquered Srem (Sirmium) the northeastern part of the Adriatic coast (Including Zara) and Zemun. Byzantium was then occupied by internal conflicts, so that there was no military response to the Hungarian conquests. In 1182, Bela III ordered an attack on Byzantine Belgrade and Braničevo.
The usurpation of Andronikos I freed Nemanja from subordination to the Byzantine emperor. Stefan Nemanja, in alliance with the Hungarian king Bela III, launched a great offensive on Byzantium in 1183. Also, the commander of the Byzantine army, Andronicus Lampardis in Niš and Braničevo, renounced obedience to the new central authorities. At the same time, the Hungarian king Bela III conquered Byzantine Belgrade, Niš and Serdica (Sofia). According to the Byzantine historian Niketas Choniates, the Serbs, led by Nemanja, joined this campaign. The following year, Nemanja launched an offensive on the southeastern Adriatic coast and conquered Byzantine Skadar and besieged Dubrovnik (Ragusa).