The unification of Czech and Slovak tribes in a single state was shattered by the Magyar invasion in 907. The Magyars, who entered the region as seminomadic pastoralists, soon developed settled agricultural communities; they held the territory until the Ottoman conquest in the sixteenth century. With the arrival of the Magyars, the Great Moravian Empire disintegrated. The chiefs of the Czech tribes in Bohemia broke from the tribes in Moravia and swore allegiance instead to the Frankish emperor Arnulf. The political center of gravity for the Czechs shifted to Bohemia, where a new political unit, the Bohemian Kingdom, would develop. The Magyars established the Kingdom of Hungary, which included a good part of the Great Moravian Empire, primarily all of modern-day Slovakia. As it turned out, the Magyar invasion had profound long-term consequences, for it meant that the Slavic people of the Kingdom of Hungary--the ancestors of the Slovaks-- would be separated politically from the western areas, inhabited by the ancestors of the Czechs for virtually a millennium. This separation was a major factor in the development of distinct Czech and Slovak nationalities.

Data as of August 1987