The Principality of Moldavia, established in 1359, was bounded by the Carpathian mountains in the west, Dniester river in the east, and Danube and Black Sea in the south. Its territory comprised the present-day territory of the Republic of Moldova, the eastern eight of the 41 counties of Romania, and the Chernivtsi oblast and Budjak region of Ukraine. Like the present-day republic and Romania's north-eastern region, it was known to the locals as Moldova. Moldavia was invaded repeatedly by Crimean Tatars and, since the 15th century, by the Turks. In 1538, the principality became a tributary to the Ottoman Empire, but it retained internal and partial external autonomy.