The history of North Macedonia can be traced to the reign of King Karan (808–778 BC), but the country was at its most powerful at the time of Philip II (359–336 BC) and Alexander the Great (336–323 BC). At the end of the 6th century AD Slavs began to settle in Macedonia. There followed a long period of internal fighting but the spread of Christianity led to consolidation and the creation of the first Macedonian Slav state, the Kingdom of Samuel, 976–1018. In the 14th century it fell to Serbia, and in 1355 to the Turks. After the Balkan wars of 1912–13 Turkey was ousted and Serbia received part of the territory, the rest going to Bulgaria and Greece. In 1918 Yugoslav Macedonia was incorporated into Serbia as South Serbia, becoming a republic in the Socialist Federal Republic of Yugoslavia. Claims to the historical Macedonian territory have long been a source of contention with Bulgaria and Greece. Macedonia (officially known as the former Yugoslav Republic of Macedonia until Feb. 2019 when it was renamed North Macedonia) declared its independence on 18 Sept. 1991. In April 1999 the Kosovo crisis which led to NATO air attacks on Yugoslavian military targets set off a flood of refugees into Macedonia, though subsequently most returned home.