of Emperor Otto I over the Magyars in 955, Slovene territory was divided into a number of border regions of the Holy Roman Empire. Carantania, being the most important, was elevated into the Duchy of Carinthia in 976. By the 11th century, the Germanization of what is now Lower Austria, effectively isolated the Slovene-inhabited territory from the other western Slavs, speeding up the development of the Slavs of Carantania and of Carniola into an independent Carantanian/Carniolans/Slovene ethnic group. By the high Middle Ages, the historic provinces of Carniola, Styria, Carinthia, Gorizia, Trieste, and Istria developed from the border regions and were incorporated into the medieval Holy Roman Empire. The consolidation and formation of these historical lands took place in a long period between the 11th and 14th centuries, and were led by a number of important feudal families, such as the Dukes of Spanheim, the Counts of Gorizia, the Counts of Celje, and, finally, the House of Habsburg. In a parallel process, an intensive Germanization significantly diminished the extent of Slovene-speaking areas. By the 15th century, the Slovene ethnic territory was reduced to its present size. In 1335, Henry of Gorizia, Duke of Carinthia, Landgrave of Carniola and Count of Tyrol died without a male heir, his daughter Margaret was able to keep the County of Tyrol, while the Wittelsbach emperor Louis IV passed Carinthia and Carniolan march to the Habsburg duke Albert II of Austria, whose mother, Elisabeth of Carinthia is a sister of the late duke Henry of Gorizia. Therefore, most of the territory of present-day Slovenia became a hereditary land of the Habsburg monarchy. As with the other component parts of the Habsburg monarchy, Carinthia and Carniola remained a semi-autonomous state with its own constitutional structure for a long time. The counts of Celje, a feudal family from this area who in 1436 acquired the title of state princes, were Habsburgs' powerful competitors for some time. This large dynasty, important at a European political level, had its seat in Slovene territory but died out in 1456. Its numerous large estates subsequently became the property of the Habsburgs, who retained control of the area right up until the beginning of the 20th century. Patria del Friuli ruled present western Slovenia until Venetian takeover in 1420. At the end of the Middle Ages, the Slovene Lands suffered a serious economic and demographic setback because of the Turkish raids. In