[2][3] Although he started his reign as vassal to Louis the German, the king of East Francia, he consolidated his rule to the extent that after 855 he was able to repel a series of Frankish attacks.

[4] Upon his initiative, brothers Cyril and Methodius, sent by the Byzantine Emperor Michael III in 863, translated the most important Christian liturgical books into Slavonic.

[11] According to the Annals of St-Bertin, in 853 Charles the Bald, king of West Francia, bribed the Bulgarians to ally with the Slavs (apparently the Moravians) and together attack Louis the German's kingdom.

However, his army plundered and burnt a great part of the province, and annihilated a not inconsiderable enemy force which attempted to storm the royal camp, but not without retaliation; after the king's return Rastiz and his men followed them and devastated the places near to the border across the Danube.In 856 Louis the German turned over the command of the southeastern marches of his kingdom to his son, Carloman with the responsibility to hold the Moravians in check.

With Rastiz's help he usurped a considerable part of his father's realm, as far as the River Inn.Pribina, the Slavic dux of Lower Pannonia, died fighting the Moravians in 861, which suggests that Carloman also had conceded this province to Rastislav.

Therefore, O lord, send us such a bishop and teacher; for from you good law issues to all countries"Rastislav's request was granted when Constantine and Methodius, two brothers who had learned the Slavic dialect spoken in Thessaloniki (Greece), arrived with a few disciples in Moravia in 863.

[31] As the Byzantine missionaries enjoyed Rastislav's protection, Louis the German dispatched Bishop Solomon of Constance to Rome where he described how the diocese of Passau had been "fragmented and brought to ruin" by the defection of the Moravians.

[34] In August 864 Louis the German invaded Moravia, crossing the Danube to besiege the civitas Dowina (identified, although not unanimously, with Devín Castle in Slovakia).

[36] Unable to escape the Frankish siege, Rastislav surrendered, turned over a numerous high-ranking hostages and swore a new oath of fidelity.

[44] By that time, according to the Annals of Fulda, Rastislav, who had earlier granted his "old city" to his nephew Svatopluk, ruled from his "indescribable fortress" that might be identified with Mikulčice (Czech Republic).

[43] In 869 Pope Hadrian II who had decided to revive the archdiocese of Illyricum consecrated Methodius archbishop of Sirmium (Sremska Mitrovica, Serbia) and papal legate of all the Slavs living in the territories ruled by Rastislav, Svatopluk and Pribina's son, Koceľ.

[50] While the assembled Franks, Bavarians, and Slavs condemned Rastislav to death for treason, the king commuted his punishment to blinding and imprisonment.