Bishop Arn of Würzburg and Abbot Sigihard of Fulda, experienced mixed results: although their forces fought well, the majority of the men were killed, and only a handful of survivors returned to East Francia. Finally a third force, consisting of Bavarians and Carantanians under Carloman's command, laid Moravian territories to waste, put Svatopluk's army to flight and forced it to take refuge in an "extremely well fortified stronghold". Svatopluk, however, soon assembled a large army and attacked the Bavarians who had been left behind under the command of Bishop Emriacho of Regensburg to guard ships on the bank of the river Danube. In May 873, Pope John VIII moved energetically to discover the whereabouts of Methodius, who was still being held prisoner in Bavaria. He sent harshly worded letters to Carloman and the Bavarian bishops, and commanded Methodius's immediate reinstatement. The Pope seems also to have brokered a lasting peace between Louis the German and Svatopluk. After his meeting with the Pope at Verona (Italy), Louis the German went to Forchheim where, according to the Annals of Fulda, "he received the legates of Svatopluk asking for a peace treaty". The exact terms of their agreement are not known, but it seems to have been a compromise: Svatopluk was forced to make an annual payment of tribute to Louis the German, who agreed to avoid any hostile acts against Great Moravia. Thus Methodius, who had in the meantime been allowed to return to Moravia, could continue his work in relatively peaceful conditions for some years. Years of expansion Great Moravia underwent considerable expansion in the 870s. For instance, the Life of Methodius refers to the capture of "a very powerful pagan prince settled on the Vistula" in territory of later Poland, and a letter written around 900 by Archbishop Theotmar of Salzburg states that Svatopluk conquered the region of Nitra, which had been thereto inhabited by pagans. Modern historiography, however, has tended to question the claims that huge neighboring territories were permanently annexed by Great Moravia. For instance, there is little clear archaeological or written evidence of a permanent extension of Moravian power in Lesser Poland or to the west in Silesia, or in Pannonia, as is suggested in earlier historical works. Svatopluk's expansionist policy was perhaps so successful because most of Western Europe was in the grip of unusually savage and large-scale Viking raids between 879 and 886. On the