The Kingdom of Bosnia (Bosnian, Croatian, and Serbian: Bosansko kraljevstvo, Босанско краљевство) was a medieval kingdom that evolved from the Banate of Bosnia (1154–1377). Its extensive, region-wide socio-economic, political and cultural influence was of great effect in the later development of medieval Balkan states, and Balkan history in general. Bosnia enjoyed de facto independence in the 13th and 14th centuries despite nominal subjection to Hungary. Its difficult terrain and remoteness enabled the Bosnians to maneuver between their two powerful neighbors, Hungary and Serbia, usually managing to avoid subordination to either. Several capable rulers allowed Bosnia briefly to play the role of a great power in the 14th century. After 1290, Bosnia enjoyed virtual independence from Hungary and gained significant territory in Dalmatia at Serbia's expense. King Tvrtko I (reigned 1353–91) acquired portions of western Serbia and most of the Adriatic coast south of the Neretva river, and during the latter part of his reign, Bosnia briefly became the strongest nation in the Balkans peninsula. However, local separatism remained strong in Bosnia, and after his death the country lost its predominance. The Ottoman Empire annexed portions of eastern Bosnia in the 1440s and 1450s, and went on to conquer Herzegovina until the last fortress fell in 1481.