Mojmir I arose in Moravia in the 820s.
Whether he was the first ruler to unite the local Slavic tribes into a larger political unit or merely came into prominence as a result of the rapidly changing political situation, is uncertain.
All the same, he had "predecessors", at least according to a letter written around 900 by Bavarian bishops to the pope.

The idea that Mojmir I was baptized between 818 and 824 is based on indirect evidence, namely on the dating of a Christian church in Mikulčice (Czech Republic) to the first quarter of the 9th century.
Although this idea is still a matter of scholarly debate, the History of the Bishops of Passau recorded a mass baptism of the Moravians in 831 by Bishop Reginhar of Passau.
Even so, the pagan sanctuary in Mikulčice continued in uninterrupted use until the middle of the 9th century.

The frontiers of the Moravian state under Mojmir I are not precisely known.
It is, however, certain that the Moravians were expanding in the 830s.
By the time the document known as the Catalogue of Fortresses and Regions to the North of the Danube was compiled sometime between 844 and 862, the Moravians already held eleven fortresses in the region.
Similarly, the Conversion of the Bavarians and the Carantanians, an historical work written in 870, relates that around 833 a local Slavic ruler, Pribina, was "driven across the Danube by Mojmir, duke of the Moravians".
Pribina was either the head of another Slavic principality or one of Mojmir I's rebellious subordinates.
Modern historians, although not unanimously, identify Pribina's lands "in Nitrava ultra Danubium" with modern Nitra (Slovakia).
Mojmir I arose in Moravia in the 820s. Whether he was the first ruler to unite the local Slavic tribes into a larger political unit or merely came into prominence as a result of the rapidly changing political situation, is uncertain. All the same, he had "predecessors", at least according to a letter written around 900 by Bavarian bishops to the pope.
The idea that Mojmir I was baptized between 818 and 824 is based on indirect evidence, namely on the dating of a Christian church in Mikulčice (Czech Republic) to the first quarter of the 9th century. Although this idea is still a matter of scholarly debate, the History of the Bishops of Passau recorded a mass baptism of the Moravians in 831 by Bishop Reginhar of Passau. Even so, the pagan sanctuary in Mikulčice continued in uninterrupted use until the middle of the 9th century.
The frontiers of the Moravian state under Mojmir I are not precisely known. It is, however, certain that the Moravians were expanding in the 830s. By the time the document known as the Catalogue of Fortresses and Regions to the North of the Danube was compiled sometime between 844 and 862, the Moravians already held eleven fortresses in the region. Similarly, the Conversion of the Bavarians and the Carantanians, an historical work written in 870, relates that around 833 a local Slavic ruler, Pribina, was "driven across the Danube by Mojmir, duke of the Moravians". Pribina was either the head of another Slavic principality or one of Mojmir I's rebellious subordinates. Modern historians, although not unanimously, identify Pribina's lands "in Nitrava ultra Danubium" with modern Nitra (Slovakia).
Mojmir I of Moravia