The lands that today comprise Croatia were part of the Austro-Hungarian Empire until the end of World War I. In 1918, the Croats, Serbs, and Slovenes formed a kingdom known after 1929 as Yugoslavia. Following World War II, Yugoslavia became a federal independent communist state consisting of six socialist republics, including Croatia, under the strong hand of Josip Broz, aka TITO. Although Croatia declared its independence from Yugoslavia in 1991, it took four years of sporadic, but often bitter, fighting before Yugoslav forces were cleared from Croatian lands, along with a majority of Croatia's ethnic Serb population. Under UN supervision, the last Serb-held enclave in eastern Slavonia was returned to Croatia in 1998. The country joined NATO in 2009 and the EU in 2013. In January 2023, Croatia further integrated into the EU by joining the Eurozone and the Schengen Area.