The Danubian Principalities (German: Donaufürstentümer, Russian: Дунайские княжества, Romanian: Principatele Dunărene) was a geopolitical term used for the Ottoman vassal principalities of Moldavia and Wallachia in the period of 1774–1858, a time of when the territories were a battleground between the Ottoman Empire, Habsburg Monarchy, and Russian Empire. While Russia returned Moldavia and Wallachia to the Ottoman Empire with the Treaty of Küçük Kaynarca (1774), it retained protectorship over the two and also of the Orthodox subjects in all of the Ottoman Empire. This made the two principalities have the status of dual authority, under Ottoman suzerainty but with Russian protection. The Russo-Turkish War (1828–1829) ended with the Russian occupation of the two principalities. The negotiations of the Great Powers in the aftermath of Russian defeat resulted in the unification of Moldavia and Wallachia in 1859.