Belarus–Ukraine relations
Belarus–Ukraine relations (, "Byelaruska-ŭkrainskiya adnosiny", , "Ukrains'ko-Bilorus'ki vidnosyny", , "Belorussko-ukrainskiye otnosheniya") are foreign relations between Belarus and Ukraine. Both countries were successively ruled by the Polish-Lithuanian Commonwealth, the Second Polish Republic, and ultimately, the Russian Empire. Prior to the 1991 breakup, both countries were part of the Soviet Union as the Belarusian SSR and Ukrainian SSR when they were the founding members of the United Nations in 1945. Being Slavic nations, both Belarus and Ukraine share closely related cultures and are predominantly inhabited by the East Slavic ethnic groups of Belarusians and Ukrainians respectively, along with a few Russians. Today, the two countries share an 891–km border.
Slavs
In the Western Balkans, South Slavs and Germanic Gepids intermarried with invaders, eventually producing a Slavicized population. In Central Europe, the West Slavs intermixed with Germanic, Hungarian, and Celtic peoples, while in Eastern Europe the East Slavs had encountered Uralic and Scandinavian peoples. Scandinavians (Varangians) and Finnic peoples were involved in the early formation of the Rus' state but were completely Slavicized after a century. Some Finno-Ugric tribes in the north were also absorbed into the expanding Rus population. In the 11th and 12th centuries, constant incursions by nomadic Turkic tribes, such as the Kipchak and the Pecheneg, caused a massive migration of East Slavic populations to the safer, heavily forested regions of the north. In the Middle Ages, groups of Saxon ore miners settled in medieval Bosnia, Serbia and Bulgaria, where they were Slavicized.