During the ninth and tenth centuries, while Bosnian-Serbian history is still so obscure, that of the Croats had achieved some prominence. The settlement of the Croats had, as we have seen, somewhat preceded the Serbian. They bordered on the coast-cities of Dalmatia, where Roman nationality and something of Roman civilization still lingered. Their relations with Byzantium were more defined, and they had also for a moment entered into the system of the renovated Empire of the West. Thus the Croats were earlier imbued with Christianity than the Serbs, and external influences were earlier at work to give their too acephalous government greater unity than their inland neighbours, still under the full sway of Sclavonic communism, could attain to. In the year 914 a Croatian Grand-Župan, Tomislav, who, in virtue of his relations to the Byzantine government and the Roman population of the Dalmatian cities, had assumed the title of ‘Consul,’ begins to be known to foreign princes as ‘King of the Croats.’ The successor of Tomislav is said to have conquered the neighbouring Serbian Banat, which from the principal river within its confines begins about this time to be known as Bosona, or Bosnia. It even became a constitutional principle in Croatia that, when the king died childless, a new king should be elected by the seven Bans of the crown-lands, one of whom was the Ban of Bosnia.[6] But this Croatian suzerainty was, as yet, premature. At the beginning of the eleventh century the Greek Emperor Basil having completed the slaughter of the Bulgarians succeeded in subjugating the Croats, and the introduction of Byzantine Governors and Protospathars into Dalmatia threw back Bosnia on to the support of her Serbian neighbours.[7] The Bosnian Ban Niklas not only accepted the Serbian Grand-Župan Dobroslav as his overlord, but aided him most efficaciously in annihilating two Byzantine armies[8] in those gorges of the Black Mountain which, from time immemorial, have been so fatal to the ambition of Stamboul.