Slovenia officially the Republic of Slovenia (Slovene: Republika Slovenija, listen is a country in Central Europe bordering Italy to the west, the Adriatic Sea to the southwest, Croatia to the south and east, Hungary to the northeast, and Austria to the north. The capital of Slovenia is Ljubljana. At various points in Slovenia's history, the country has been part of the Roman Empire, partly the Republic of Venice, the principality Carantania (only modern Slovenia's northern part), the Holy Roman Empire, the Habsburg Monarchy, the Austrian Empire (later known as Austria-Hungary), the State of Slovenes, Croats and Serbs, the Kingdom of Serbs, Croats and Slovenes (renamed to Kingdom of Yugoslavia in 1929); partly Kingdom of Italy, between the two World Wars, occupied by Germany, Italy, Hungary and Independent State of Croatia (1941-1945), and the Socialist Federal Republic of Yugoslavia from 1945 until gaining independence in 1991. Slovenia is a member of the European Union, the Eurozone, the Schengen area, the Organization for Security and Co-operation in Europe, the Council of Europe and NATO. Slavic ancestors of the present-day Slovenes settled in the area in the 6th century. The Slavic principality Carantania was formed in the 7th century. In 745, Carantania was incorporated into the Carolingian Empire, while Carantanians and other Slavs living in present Slovenia converted to Christianity. Carantania retained its internal independence until 828 when the local princes were deposed following the anti-Frankish rebellion of Ljudevit Posavski and replaced by a German (mostly Bavarian) ascendancy. Under Emperor Arnulf of Carinthia, Carantania, now ruled by a mixed Bavarian-Slav nobility, shortly emerged as a regional power, but was destroyed by the Hungarian invasions in the late 9th century. Coat of arms of Carniola, a historical region within Austria-HungaryCaran tania was established again as an autonomous administrative unit in 976, when Emperor Otto I, "the Great", after deposing the Duke of Bavaria, Henry II, "the Quarreller", split the lands held by him and made Carinthia the sixth duchy of the Holy Roman Empire, but old Carantania never developed into a unified realm. In the century of the second millennium protecting marches were established at the south-eastern borders of the Empire, which in the course of time developed into duchies in their right: Styria, Carniola and Friuli, into which the Slovene Lands remained divided up to 1918.[citation needed] The Carantanian identity remained alive into the 12th century[citation needed] when it was slowly replaced by regional identities. The first mentions of a common Slovene ethnic identity, transcending regional boundaries, date from the 16th century. During the 14th century, most of Slovene Lands passed under the Habsburg rule. In the 15th century, the Habsburg domination was challenged by the Counts of Celje, but by the end of the century the great majority of Slovene-inhabited territories were incorporated into the Habsburg Monarchy. Most Slovenes lived in the region known as Inner Austria, forming the majority of the population of the Duchy of Carniola and the County of Gorizia and Gradisca, as well as of Lower Styria and southern Carinthia. Slovenes also inhabited most of the territory of the Imperial Free City of Trieste, although representing the minority of its population. Slovene majorities also existed in the Prekmurje region of the Kingdom of Hungary, and in Venetian Slovenia and north-western Istria, which were part of the Republic of Venice. In the 16th century, the Protestant Reformation spread throughout the Slovene Lands. During this period, the first books in Slovene language were written by the Protestant preacher Primoz Trubar and his followers, establishing the base for the development of the Slovene standard language.