Croatia, officially the Republic of Croatia is a country at the crossroads of Central and Southeast Europe, on the Adriatic Sea. Its capital Zagreb forms one of the country's primary subdivisions, along with twenty counties. Croatia has an area of 56,594 square kilometres and a population of 4.28 million, most of whom are Roman Catholics.
The Croats arrived in the area in the 6th century and organised the territory into two duchies by the 9th century. Tomislav became the first king by 925, elevating Croatia to the status of a kingdom, which retained its sovereignty for nearly two centuries, reaching its peak during the rule of kings Petar Krešimir IV and Dmitar Zvonimir. Croatia entered a personal union with Hungary in 1102. In 1527, faced with Ottoman conquest, the Croatian Parliament elected Ferdinand I of Habsburg to the Croatian throne. In October 1918, in the final days of World War I, the State of Slovenes, Croats and Serbs, independent from Austria-Hungary, was proclaimed in Zagreb, and in December 1918 it was merged into the Kingdom of Serbs, Croats and Slovenes.