He turned against East Francia and supported the rebellion of Ratpot, the deposed prefect of the March of Pannonia, against Louis the German in 853. The Frankish monarch retaliated by invading Moravia in 855. According to the "Annals of Fulda", the Moravians were "defended by strong fortifications", and the Franks withdrew without defeating them, though the combats lasted until a peace treaty was worked out in 859. The truce is regarded as a stalemate and shows the growing strength of Rastislav's realm. Conflicts between Moravia and East Francia continued for years. For instance, Rastislav supported Louis the German's son, Carloman, in his rebellion against his father in 861. The first record of a raid by the Magyars in Central Europe seems to have been connected to these events. According to the "Annals of St. Bertin", "enemies called Hungarians" ravaged Louis the German's kingdom in 862, which suggests that they supported Carloman.