Towards the end of the eighth century, after the decline of the power of the Avars, Charlemagne extended his conquests eastwards (he made a great impression on the minds of the Slavs, whose word for king, _kral_ or _korol_, is derived directly from his name), and his son Louis conquered the Serbs settled in the country between the rivers Save and Drave. This is commemorated in the name of the mass of hill which lies between the Danube and the Save, in eastern Slavonia, and is to this day known as _Fruška Gora_, or French Hill. The Serbs and Bulgars fought against the Franks, and while the Bulgars held their own, the Serbs were beaten, and those who did not like the rule of the new-comers had to migrate southwards across the Save; at the same time the Serbs between the rivers Morava and Timok (eastern Serbia) were subjected by the Bulgars. With the arrival of the Magyars, in the ninth century, a wall was raised between the Serbs and central and western Europe on land. Croatia and Slavonia (between the Save and the Drave) were gradually drawn into the orbit of the Hungarian state, and in 1102, on the death of its own ruler, Croatia was absorbed by Hungary and has formed part of that country ever since. Hungary, aiming at an outlet on the Adriatic, at the same time subjected most of Dalmatia and parts of Bosnia. In the west Venice had been steadily growing in power throughout the tenth century, and by the end of it had secured control of all the islands off Dalmatia and of a considerable part of the coast. All the cities on the mainland acknowledged the supremacy of Venice and she was mistress of the Adriatic. In the interior of the Serb territory, during the eleventh and twelfth centuries, three political centres came into prominence and shaped themselves into larger territorial units. These were: (1) Raska, which had been Caslav’s centre and is considered the birth-place of the Serbian state (this district, with the town of Ras as its centre, included the south-western part of the modern kingdom of Serbia and what was the Turkish _sandjak_ or province of Novi-Pazar); (2) Zeta, on the coast (the modern Montenegro); and (3) Bosnia, so called after the river Bosna, which runs through it. Bosnia, which roughly corresponded to the modern province of that name, became independent in the second half of the tenth century, and was never after that incorporated in the Serbian state. At times it fell under Hungarian influence; in the twelfth century, during the reign of Manuel Comnenus, who was victorious over the Magyars, Bosnia, like all other Serb territories, had to acknowledge the supremacy of Constantinople.