De Administrando Imperio described the polity of Zachlumia as: "From Ragusa begins the domain of the Zachlumi (Ζαχλοῦμοι) and stretches along as far as the river Orontius: and on the side of the coast it is neighbour to the Pagani, but on the side of the mountain country it is neighbour to the Croats on the north and to Serbia at the front ... Those who live there now, Zachlumi, are Serbs, from the time of that prince who claimed the protection of the Emperor Heraclius.The principality sprang from Dalmatia (Croatia) to the northwest and Pagania to the west; to the mountain of Kalinovik and the Gatačko polje, where it bordered Travunia.[6] In the second decade of the 7th century, the Avars and their Slavic subjects occupied most of the Byzantine province of Dalmatia, including the territory of what would become Zahumlje, sacking towns and enslaving or displacing the local population.[9][10][11][12][13][14] According to Noel Malcolm, today's western Serbia was area where Serbs settled in 7th century and from there they expanded their rule on territory of Zachlumia.[18] Michael's tribal origin is related to the oral tradition from Historia Salonitana by Thomas the Archdeacon about seven or eight tribes of nobles called Lingones who arrived from Poland and settled in Croatia.[23] According to Thomas the Archdeacon, when describing the reign of Croatian king Stephen Držislav in the late 10th century, notes that Duchy of Hum (Zachlumia or Chulmie) was a part of the Kingdom of Croatia, before and after Stjepan Držislav: "Istaque fuerunt regni eorum confinia: ab oriente Delmina, ubi fuit civitas Delmis, ... ab occidente Carinthia, versus mare usque ad oppidum Stridonis, quod nunc est confinium Dalmatie et Ystrie; ab aquilone vero a ripa Danubii usque ad mare Dalmaticum cum tota Maronia et Chulmie ducatu."[27] Finally, the 866–867 Saracens' siege of Dubrovnik, which lasted fifteen months, was raised due to the intervention of Basil I, who sent a fleet under the command of Niketas Oryphas in relief of the city.[29] These small cities in the region (also Dyrrachium) did not stretch into the hinterlands, and had none military capacity, thus Basil I paid a tax of '72 gold coins' to the princes of Zahumlje and Travunia.A neighbour of Croatian Kingdom and Principality of Serbia as well as an ally of Bulgaria, he was nevertheless able to maintain independent rule throughout at least a good part of his reign.[10] Michael have come into territorial conflict with the neighbouring prince Peter Gojniković, the ruler of inner Serbia, who was extending his power westwards.[30][31] To eliminate that threat and as a close ally of Bulgaria, Michael warned the Bulgarian Tsar Simeon I about the alliance between Peter and Symeon's enemy, the Byzantine Empire.[30] In 912 Michael kidnapped the Venetian Doge's son Peter Badoari that was returning to Venice from Constantinople and sent him to Czar Simeon as a sign of loyalty.[32] The Historia Salonitana maior, whose composition may have begun in the late 13th century,[33] cites a letter of Pope John X to Tomislav, "king (rex) of the Croats", in which he refers to the first council in some detail.In this letter, John describes Michael as "the most excellent leader of the Zachlumi" (excellentissimus dux Chulmorum),[34][35] and is mentioned the Ston bishopric (ecclesia Stagnensis) which jurisdiction remained under Split until 1022.The Bulgarian army then attacked Croatia in support of the rebel princes Krešimir III and Gojslav and advanced northwest as far as Split, Trogir and Zadar, then northeast through Bosnia and Raška and returned to Bulgaria.According to historian Paul Stephenson, it "suggests that he had been courted by the emperor, and awarded nominal rights neighbouring lands, including Duklja, which was at the time at war with the empire.[46] During the rule of Constantine Bodin (r. 1081–1101), neither Bosnia, Serbia nor Zahumlje was ever integrated into Doclea, each retained its own nobility and institutions and simply acquired a Vojislavljević to head the local structure as Prince or Duke.[52] He refused to allow Rainer, Latin Archbishop of Spalato (Split) whom he considered to be an agent of Hungarian king, to consecrate a bishop for the town of Ston.[52] In 1190–1192, Stefan Nemanja briefly assigned the rule of Hum to his son Rastko Nemanjić, while Miroslav held the Lim region with Bijelo Polje.[53] Latin vengeance came in March 1198, when Andrew II of Hungary become the prince of Dalmatia, Croatia and Hum, while Miroslav died a year after and his wife was living in exile.[59] But seeking to centralize his realm, Stephen Uroš I of Serbia tried to stamp out regional differences by dropping references to Zahumlje (Hum), Trebinje and Duklja (Zeta), and called himself "King of all Serbian land and the Coast".[51][74] In contrast to Bosnia, where Roman Catholicism and Bosnian Church were firmly established, eastern parts of Hum was mostly Orthodox, from 13th century and the rise of Nemanjići.[75] In the 14th- and 15th centuries, there was an influx of settlers from the župa of Trebinje, around forts Klobuk, Ledenica and Rudina, and the Hum lands around Gacko and Dabar, to Kotor.Also, the honorific title Grand Voivode (Duke) of Zahumlije has been granted at times to junior members of the Petrović-Njegoš dynasty that ruled in Montenegro until 1918.