<P> To the southwest, the principality of Halych had developed trade relations with its Polish, Hungarian and Lithuanian neighbours and emerged as the local successor to Kievan Rus' . In 1199, Prince Roman Mstislavych united the two previously separate principalities . In 1202 he conquered Kiev, and assumed the title of Knyaz of Kievan Rus', which was held by the rulers of Vladimir - Suzdal since 1169 . His son, Prince Daniel (r . 1238--1264) looked for support from the West . He accepted a crown as a "Rex Rusiae" ("King of Rus") from the Roman papacy, apparently doing so without breaking with Constantinople . In 1370, the patriarch of the Eastern Orthodox Church in Constantinople granted the King of Poland a metropolitan for his Ruthenian subjects . Lithuanian rulers also requested and received a metropolitan for Novagrudok shortly afterwards . Cyprian, a candidate pushed by the Lithuanian rulers, became Metropolitan of Kiev in 1375 and metropolitan of Moscow in 1382; this way the church in the Russian countries was reunited for some time . In 1439, Kiev became the seat of a separate "Metropolitan of Kiev, Halych and all Rus"' for all Greek Orthodox Christians under Polish - Lithuanian rule . </P> <P> However, a long and unsuccessful struggle against the Mongols combined with internal opposition to the prince and foreign intervention weakened Galicia - Volhynia . With the end of the Mstislavich branch of the Rurikids in the mid-14th century, Galicia - Volhynia ceased to exist; Poland conquered Halych; Lithuania took Volhynia, including Kiev, conquered by Gediminas in 1321 ending the rule of Rurikids in the city . Lithuanian rulers then assumed the title over Ruthenia . </P> <P> The state finally disintegrated under the pressure of the Mongol invasion of Rus', fragmenting it into successor principalities who paid tribute to the Golden Horde (the so - called Tatar Yoke). In the late 15th century, the Muscovite Grand Dukes began taking over former Kievan territories and proclaimed themselves the sole legal successors of the Kievan principality according to the protocols of the medieval theory of translatio imperii . </P> <P> On the western periphery, Kievan Rus' was succeeded by the Principality of Galicia - Volhynia . Later, as these territories, now part of modern central Ukraine and Belarus, fell to the Gediminids, the powerful, largely Ruthenized Grand Duchy of Lithuania drew heavily on Rus' cultural and legal traditions . Due to the fact of the economic and cultural core of Rus' being located on the territory of modern Ukraine, Ukrainian historians and scholars consider Kievan Rus' to be a founding Ukrainian state . </P>

Which group ended the period of kievan rus dominance