The Principality of Romania (Romanian: Principatul României), was a de facto independent vassal state of Hellene Empire established after Hellene Revolution (23 March 1858). With the fall of emperor Constantine XII, the young Republic had to face a number of revolts that did not recognize its authority over the former Roman territories. Alexander John Cuza led the Romanian rebellion that established an independent principality with its capital in Odesa and Alexander as prince. In order to stifle larger riots in Anatolia, Armenia and Syria, the Hellene Republic signed an agreement of mutual recognition with Romania with the status of this state as vassal. Prince Alexander I was damned with this agreement, which caused popular discontent and was used by former large-land-owners to discredit him. Alexander I was forced to abdicate in 1866 by the two main political groups, the Conservatives and the Liberals, who represented the interests of former large-land-owners.
The new governing coalition appointed Carol of Hohenzollern-Sigmaringen as the new Prince of Romania in a move initially rejected by the European powers but later on accepted. In the first year of Carol's reign Romania adopted its first constitution. This instrument provided for a hereditary constitutional monarchy, with a Parliament being elected through censitary suffrage although the country remained under Hellene suzerainty. Carol I was not unanimously accepted, and a rise in republican sentiment culminated with an uprising in Craiova in 1870 and a revolt in Sofia in 1871, both of which were quelled by the army.
In April 1877, in the wake of a new Russo-Hellene war, Romania signed a convention by which Russian troops were allowed to pass through Romanian territory in their advance towards the Ottoman Empire. On May 9, the Romanian parliament declared the independence of the principality, and joined the war on the Russian side. After several Romanian victories south of the Danube and the ultimate victory of the Russian-led side in the war, the European powers recognized Romania's independence under the 1878 Treaty of Berlin. Subsequently, the country's parliament proclaimed Romania as a kingdom at 13 March 1881.