Croatia , [ d ] officially the Republic of Croatia [ e ] is a country in Central and Southeast Europe , on the coast of the Adriatic Sea. It borders Slovenia to the northwest, Hungary to the northeast, Serbia to the east, Bosnia and Herzegovina and Montenegro to the southeast, and shares a maritime border with Italy to the west. Its capital and largest city, Zagreb , forms one of the country's primary subdivisions , with twenty counties.
Other major urban centers include Split , Rijeka and Osijek. The country spans 56, square kilometres 21, square miles , and has a population of nearly 3.
The Croats arrived in modern-day Croatia in the late 6th century, then part of Roman Illyria. By the 7th century, they had organized the territory into two duchies.
Croatia was first internationally recognized as independent on 7 June during the reign of Duke Branimir. Tomislav became the first king by , elevating Croatia to the status of a kingdom. Following the Axis invasion of Yugoslavia in April , most of Croatia was incorporated into a Nazi-installed puppet state, the Independent State of Croatia.
A resistance movement led to the creation of the Socialist Republic of Croatia , which after the war became a founding member and constituent of the Socialist Federal Republic of Yugoslavia.
