History of Transylvania union of Transylvania with Romania in Alba Iulia on 1. December 1918.; Bessarabia, having declared independence from Russia in 1917 at the Conference of the Country (Sfatul Țării), called in Romanian troops to protect the province from the Bolsheviks. The union of the Transylvania, Maramureș, Crișana and Banat regions with the Old Kingdom of Romania was ratified in 1920 by the Treaty of Trianon, which recognised the sovereignty of Romania over these regions and settled the border between the Republic of Hungary and the Kingdom of Romania. The union of Bukovina and Bessarabia with Romania was ratified in 1920 by
Transylvania 1526, Transylvania was a voivodeship in the Kingdom of Hungary, led by a voivode appointed by the King of Hungary. After the Battle of Mohács in 1526, Transylvania became part of the Kingdom of János Szapolyai. Later, in 1570, the kingdom transformed into the Principality of Transylvania, which was ruled primarily by Calvinist Hungarian princes. During that time, the ethnic composition of Transylvania transformed from an estimated near equal number of the ethnic groups to a Romanian majority. Vasile Lupu estimates their number already more than one-third of the population of Transylvania in a letter to the sultan around 1650.