After the unsuccessful 1848 revolution, the Great Powers rejected the Romanians' desire to officially unite in a single state, forcing the Romanians to proceed alone in their struggle against the Ottoman Empire.^[74]

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 fully, Russia. While the Moldavia-Wallachia unionist campaign, which had come to dominate political demands, was accepted with sympathy by the French, Russians, Prussians, and Sardinians, it was rejected by the Austrian Empire, and looked upon with suspicion by Great Britain and the Ottomans.

Negotiations amounted to an agreement on a minimal formal union, to be known as the United Principalities of Moldavia and Wallachia but with separate institutions and thrones and with each principality electing its own prince. The same convention stated that the army would keep its old flags, with the addition of a blue ribbon on each of them. However, the Moldavian and Wallachian elections for the ad-hoc divans in 1859 profited from an ambiguity in the text of the final agreement, which, while specifying two separate thrones, did not prevent the same person from occupying both thrones simultaneously and ultimately ushered in the ruling of Alexandru Ioan Cuza as Domnitor (Ruling Prince) over both Moldavia and Wallachia from 1859 onwards, uniting both principalities.^[75]

Alexander Ioan Cuza carried out reforms including abolishing serfdom and started to unite the institutions one by one in spite of the convention from Paris. With help from unionists, he unified the government and parliament, effectively merging Wallachia and Moldavia into one country and in 1862 the country's name was changed to United Principalities of Romania.