Montenegro was founded as a state under its present name in 15th century, continuing the tradition of the Slavic state of Duklja. It was able to maintain its independence during the reign of the Ottoman Empire in the Balkans, as its independence was formally acknowledged at the Congress of Berlin in 1878. After the World War I, fighting for the Allied powers, it was absorbed into the Kingdom of Serbs, Croats, and Slovenes, which later became the Kingdom of Yugoslavia in 1929. Montenegro was also later part of various incarnations of Yugoslavia, until it regained its full independence from the federation of Serbia-Montenegro on the June 2006 referendum. Montenegro was the only subsequent republic of the former Yugoslavia that supported Serbia during the wars of the Former Yugoslavia in the 1990s.