the Ottoman Empire and which resulted in the unification of both principalities. On , Moldavia and Wallachia formally united to create the Romanian United Principalities, the core of the Romanian nation state. In February 1866, Prince Cuza was forced to abdicate and go into exile by a political coalition led by the Liberals; the German Prince Karl of Hohenzollern-Sigmaringen was offered the Throne and, on he entered Bucharest for the first time. In July the same year, a new constitution came into effect, giving the country the name of Romania; internationally, this name was used only after 1877, since at the time the foreign policy of the state was drafted by the Ottomans. Nominally, the new state remained a vassal of the Ottoman Empire. However, by this time the suzerainty of the Sublime Porte had become a legal fiction. Romania had its own flag and anthem; after 1867, it had its own currency as well. On , Romania proclaimed itself fully independent; the proclamation was sanctioned by the Domnitor the following day. Four years later, the 1866 constitution was modified and Romania became a kingdom, on , Domnitor Carol I was crowned as the first King of Romania. After the First World War, Transylvania and other territories were also included. For its triple symbolic meaning, the date of May 10 was celebrated as Romania's National Day until 1948, when the Communist regime installed the republic on 30 December 1947. Background As a historical term designating the pre-Union Principalities of Moldavia and Wallachia, sometimes including the Principality of Transylvania, the term "Romanian Principalities" dates back to the beginnings of modern Romanian history in the mid-19th century. It was subsequently used by Romanian historians as an alternative to the much older term "Romanian Lands". English use of "Romanian Principalities" is documented from the second half of the 19th century. In the period between the late 18th century and the 1860s, Danubian Principalities was used, a term that sometimes included Serbia, but not Transylvania. In contrast, use of "Romanian Principalities" sometimes included Transylvania but never Serbia. History The aftermath of the Russian Empire's defeat in the Crimean War brought the 1856 Treaty of Paris, which started a period of common tutelage for the Ottomans and a Congress of Great Powers—the United Kingdom of Great Britain and Ireland, the Second French Empire, the Kingdom of Piedmont-Sardinia, the Austrian Empire, Prussia, and, though never again