The nation's modern history began with that of the East Slavs. From at least the 9th century, the territory of Ukraine was a center of the medieval East Slavic civilization. This state, known as the Kievan Rus' became the largest and most powerful nation in Europe, but disintegrated in the 12th century. From the 14th century on, the territory of Ukraine was divided among a number of regional powers, and by the 19th century, the largest part of Ukraine was integrated into the Russian Empire, with the rest under Austro-Hungarian control. After a chaotic period of incessant warfare and several attempts at independence (1917–21) following World War I and the Russian Civil War, Ukraine emerged in 1922 as one of the founding republics of the Soviet Union.