Charles Bowlus says that a letter, written by Theotmar, Archbishop of Salzburg and his suffragan bishops in about 900, strongly suggests that Nitra was only conquered by Svatopluk I of Moravia only in the 870s.
The development of the Hunnic Empire in the Eurasian Steppes forced large groups of Germanic peoples, including the Quadi and the Vandals, to leave their homelands by the Middle Danube and along the upper course of the river Tisza in the early The 6th-century Byzantine historian, Procopius, wrote of a group of the Heruli who had "passed through the territory of all of the Sclavenes", or Slavs, during their migration towards the northern "Thule".
Procopius also wrote of an exiled Longobard prince, Hildigis, who first fled to the "Sclaveni" and then to the Gepids, "taking with him not only those of the Longobards who had followed him, but also many of the Sclaveni" The Longobards and the local Slavs remained separated by the natural border formed by Little and White Carpathians, respected by both sides according to Ján Steinhübel.
In 880, Pope John VIII set up an independent ecclesiastical province in Great Moravia with Archbishop Methodius as its head.
He also named the German cleric Wiching the Bishop of Nitra.
Rastislav was also preoccupied with the security and administration of his state.
Numerous fortified castles built throughout the country are dated to his reign and some of them (e.g., Dowina - Devín Castle) The rebellious prince allied himself with the Franks and overthrew his uncle in 870.The Slavs in southern Slovakia adopted new burial rite (inhumation), jewelry, fashion and used also common cemeteries with the Avars.Large Slavo-Avaric cemeteries can be found in Devínska Nová Ves and Záhorská Bystrica near Bratislava and similar cemeteries, the proof of direct Avar power, south of the line Devín-Nitra-Levice-Želovce-Košice-Šebastovce.He also writes that the Slavs, who remained "an independent third party" in strained Longobard-Gepid relations, were not interested in conflicts with their Germanic neighbours, but made raids in the faraway Byzantine Empire. Barford, these features suggest that the Carpathian Mountains and the Sudetes separated the ancestors of the Slovaks and the Czechs from the Slavs living to the north of those mountains.Further migration waves strengthened the local Slavic population because new Slavic groups, pressed by the Avars, crossed the Eastern Carpathians, seceding from the Slavs who continued their expansion to the Balkan Peninsula. According to the same chronicle, the Wends rose up in rebellion against their Avar masters and elected a Frankish merchant, Samo, their king "in the fortieth year of Clothar's reign", that is in 623 or 624.The political and cultural development in Slovakia continued in two separate lines.