Croatia's history is simply fascinating. Of the many groups that once inhabited the lands of contemporary Croatia, the oldest you will likely hear about dates back some 1200 years ago, when Croatia was inhabited by a group of tribes commonly referred to as the Illyrians. Some present-day Croatian cities were established by the ancient Illyrians. Centuries later, the trade-loving Ancient Greeks arrived and set up colonies on the Adriatic islands of Vis, Korcula and Hvar. To establish firmer control over the Illyrians, the Greeks requested backup from the Romans, who by that point were steadily growing in power and gaining territory throughout Western Europe.
Though the Illyrians did battle it out with the Romans, ultimately they lost, and the Romans continued their colonization of Croatia, dubbing the new province "Illyricum." Roman legions, which often did more building than soldiering, established more cities and constructed roads, aqueducts, amphitheaters and citadels. One Roman Emperor, Diocletian, liked Croatia's mesmerizing shores so much that he commissioned a massive palace for his retirement in the coastal city of Split.
As with most of Europe, as the Roman Empire was collapsing and the Dark Ages were commencing, "barbarian" invaders also showed up in Croatia. While the facts are murky, historians believe that it was around this time that the Slavic Croats showed up and began settling in Croatia most likely in several waves. While their origins are unclear, several theories are based on the idea that the Croats came from the territories in today's Poland and Ukraine and migrated south to Croatia. The cultural differences that we see today in Croatia coastal, Mediterranean versus interior, Central European date back to this era when the Croats ruled from two distinctly different bases of power. By the end of the first millennium, Croatia was united and ruled by one king.
After a few centuries of stable rule, late-medieval alliances with Hungary and invasions from the powerful maritime Republic of Venice (who wanted control of the ports on Croatia's seaboard) saw an increasingly fragmented Croatia, often subjected to the tight grip of a foreign ruler. By the 15th century, Croatia became part of the powerful Hapsburg Empire, which sought not just in Croatia but in all their territories to push back the biggest threat to Christian, Central Europe of the era: the Ottoman Turks. Once the Ottomans were defeated, the Croats who were still longing for self-rule saw that the Austrians, Hungarians, Venetians and now Orthodox Russians were all vying for influence and control in their lands.
By the 19th century, Croatian nationalism (pride for the Croatian language and the country's Slavic culture) was brewing, and the Croats were able to gain more autonomy from the Austrians and Hungarians. Croatia's leaders could not however agree on how the country should progress. Some envisioned a united Croatia, while others wanted to unite the Southern Slavs. Tensions between the Catholic Croats and the Orthodox Serbs were on the rise. These cultural, religious tensions paired with the political ambitions of the Austro-Hungarian Empire and the growing number of alliances formed between the world's most powerful countries proved to be too volatile a mix, and when a Bosnian Serb assassinated the Hapsburg heir (Archduke Franz Ferdinand) in Sarajevo in 1914, Europe was frantically hurled into World War I.
At the end of the war, upon seeing the defeat of their Austro-Hungarian rulers, the Croats, Serbs and Slovenes united to create a kingdom. Just ten years later, violence broke out between the groups. A Serbian-dominated dictatorship was formed, and the kingdom's name was changed to Yugoslavia. During WWII, Croatia as part of Yugoslavia suffered from both external (Nazi) forces as well as internal forces. Warring between different Croatian factions and between Croats and Serbs continued, and at the end of WWII, the communist party won the elections. After nearly four decades of communist rule, by the late 1980s, ideologies in Croatia were turning away from Communism and towards democracy, and differences in political ideology, religion and ethnicity continued to plague Yugoslavia. In 1991 Croatia declared its independence. The knowledge that Yugoslavia was on its last leg caused the region to erupt in a firestorm of violence (including genocide) between the Serbs, Croats and Bosnians. Peace finally arrived in 1995, and since then Croatia has looked forward to a brighter future. It is now a member of the European Union.
Important historical sights to visit in Croatia include the historic center of Porec, the historic city of Trogir, the historical complex of Split (including the Palace of Diocletian), the Old Town of Dubrovnik, the Stari Grad Plain on the island of Hvar and the Cathedral of St. James in Šibenik. They are all UNESCO World Heritage Sites.