Byzantine Empire, lived in so-called Sklavinia ("Slav lands"), territories initially out of Byzantine control and independent. In the 8 century, the Vlastimirović dynasty established the Serbian Principality. In 822, Serbia "stretched over the greater part of Dalmatia", and Christianity was adopted as state-religion in ca 870. In the mid 10 century the state had emerged into a tribal confederation that stretched to the shores of the Adriatic Sea by the Neretva, the Sava, the Morava, and Skadar. The state disintegrated after the death of the last known Vlastimirid ruler – the Byzantines annexed the region and held it for a century, until 1040 when the Serbs under the Vojislavljević dynasty revolted in Duklja (Pomorje). In 1091, the Vukanović dynasty established the Serbian Grand Principality, based in Rascia (Zagorje). The two halves were reunited in 1142.
In 1166, Stefan Nemanja assumed the throne, marking the beginning of a prospering Serbia, henceforth under the rule of the Nemanjić dynasty. Nemanja's son Rastko (posth. Saint Sava), gained autocephaly for the Serbian Church in 1217 and authored the oldest known constitution, and in the same year Stefan II was crowned King, establishing the Serbian Kingdom. The Mrnjavčević, Lazarević and Branković dynasties ruled the Serbian lands in the 15th and 16th centuries. Constant struggles took place between various Serbian provinces and the Ottoman Empire. After the fall of Constantinople to the Ottomans in 1453 and the Siege of Belgrade, the Serbian Despotate fell in 1459 following the siege of the provisional capital of Smederevo. The Smederevo Fortress is the largest medieval lowland type of fortresses in Europe. After repelling Ottoman attacks for over 70 years, Belgrade finally fell in 1521, opening the way for Ottoman expansion into Central Europe. Taking advantage of the Byzantine civil war of 1341–1347, Dušan doubled the size of his kingdom seizing territories to the south, southeast and east
