Romania, formerly also spelled Roumania and Rumania, is a country located at the crossroads of Southeastern and Central Europe, on the Lower Danube, north of the Balkan Peninsula and the western shore of the Black Sea. Romania shares a border with Hungary and Serbia to the west, Ukraine and Moldova to the northeast and east, and Bulgaria to the south. At 238,391 square kilometres, Romania is the ninth largest country of the European Union by area, and has the 7th largest population of the European Union with 20,121,641 people. Its capital and largest city is Bucharest – the 6th largest city in the EU.The United Principalities emerged when the territories of Moldavia and Wallachia were united under Prince Alexander Ioan Cuza in 1859. In 1866 Prince Karl of Hohenzollern-Sigmaringen was called to the throne as the Ruling Prince of the Romanian Principate and in 1881 he was finally crowned as King Carol I, the first monarch of the Kingdom of Romania. Independence from the Ottoman Empire was declared on 9 May 1877, and was internationally recognised the following year. At the end of World War I, Transylvania, Bukovina and Bessarabia united with the Kingdom of Romania.Following the outbreak of World War II on 1 September 1939, the Kingdom of Romania under King Carol II officially adopted a position of neutrality. In summer 1940, a series of territorial disputes were resolved unfavorably to Romania, resulting in the loss of most of the territory gained in the wake of World War I. This caused the popularity of Romania's government to plummet. World War II gave cause to the rise of a military dictatorship in Romania under far-right Marshal Ion Antonescu, who chose to fight on the side of the Axis powers from 1941-44 in order to regain the provinces. After his removal, Romania switched sides in 1944 and joined the Allies. By the end of the war, some formerly Romanian northeastern territories were occupied by the Soviet Union, with Red Army units stationed on Romanian soil. In 1947 Romania forcibly became a People's Republic and a member of the Warsaw Pact. In 1965 Nicolae Ceaușescu became General Secretary of the Romanian Workers' Party, and the harsh austerity measures, political repression, and cult of personality he implemented led to the Socialist Republic of Romania becoming the most Stalinist police state in the Eastern bloc. Eventually his authoritarian government was toppled in December 1989 during the Romanian Revolution.With the fall of the Iron Curtain, Romania began its transition towards democracy and a capitalist market economy. After a decade of post-revolution economic problems and living-standards decline, extensive reforms fostered economic recovery. As of 2010, Romania is an upper-middle income country with a high Human Development Index. Romania joined NATO on 29 March 2004, and the European Union on 1 January 2007. It is a member of the Latin Union, Francophonie, OSCE, WTO, BSEC, United Nations, etc. Romania is a unitary semi-presidential republic, in which the executive branch consists of the President and the Government.