Kingdom of Galicia–VolhyniaUkraine
A successor state to the Kievan Rus' on part of the territory of today's Ukraine was the Principality of Galicia-Volhynia. Previously, Vladimir the Great had established the cities of Halych and Ladomir as regional capitals. This state was based upon the Dulebe, Tiverian and White Croat tribes.
The state was ruled by the descendants of Yaroslav the Wise and Vladimir Monomakh. For a brief period, the state was ruled by a Hungarian nobleman. Battles with the neighbouring states of Poland and Lithuania also occurred, as well as internecine warfare with the independent Ruthenian Principality of Chernihiv to the east. At its greatest extension the territory of Galicia-Volhynia included later Wallachia/Bessarabia, thus reaching the shores of the Black Sea.
During this period (around 1200–1400), each principality was independent of the other for a period. The state of Halych-Volynia eventually became a vassal to the Mongol Empire, but efforts to gain European support for opposition to the Mongols continued. This period marked the first "King of Rus'"; previously, the rulers of Rus' were termed "Grand Dukes" or "Princes."