Slovakia is a landlocked country situated in Central Europe, with Hungary to its south and Poland on its north. Slovakia fell under Hungarian rule in the early tenth century. The dissolution of the Austro-Hungarian Empire at the close of World War I allowed the Slovaks to join the closely related Czechs to form Czechoslovakia in 1918. Following World War II, Czechoslovakia became a Communist nation within Soviet-dominated Eastern Europe. With the collapse of the Soviet Union in 1989, Czechoslovakia regained its freedom. In January 1993, Czechoslovakia was broken up and the Czech Republic and the Slovak Republic were simultaneously and peacefully founded. With successful reforms as part of its transition from a centrally-planned economy to a market-oriented one, Slovakia has been among the best economic performers in Central and Eastern Europe in recent years. It joined the European Union in May of 2004, and adopted the euro in January of 2009.