Transylvania as originally defined in Treaty of Trianon, 27 years earlier, thus confirming the return of Northern Transylvania to Romania. From 1947 to 1989, Transylvania, along with the rest of Romania, was under a communist regime. The ethnic clashes of Târgu Mureș occurred between ethnic Romanians and Hungarians in March 1990 after the fall of the communist regime and became most notable inter-ethnic incident in the post-communist era. The Transylvanian Plateau, high, is drained by the Mureș, Someș, Criș, and Olt rivers, as well as other tributaries of the Danube. This core of historical Transylvania roughly corresponds with nine counties of
Transylvania the Romanians). The Magyars conquered much of Central Europe at the end of the 9th century. According to Gesta Hungarorum, the Vlach voivode Gelou ruled Transylvania before the Hungarians arrived. The Kingdom of Hungary established partial control over Transylvania in 1003, when king Stephen I, according to legend, defeated the prince named "Gyula". Some historians assert Transylvania was settled by Hungarians in several stages between the 10th and 13th centuries, while others claim that it was already settled, since the earliest Hungarian artifacts found in the region are dated to the first half of the 10th century. Between 1003 and