During the "Wilhelminer War"a civil war between two factions of local noblemen in the March of Pannonia which lasted from 882 and 884Svatopluk "collected troops from all the Slav lands" and invaded Pannonia. According to the Bavarian version of the "Annals of Fulda", the Moravians' invasion "led to Pannonia's being laid waste" to the east of the river Rába. However, Regino of Prüm states that it was Arnulf of Carinthia who maintained control over Pannonia in 884. Svatopluk had a meeting with Emperor Charles the Fat (r. 881–888) at Tulln an der Donau in Bavaria in 884. At the meeting, ""dux"" Svatopluk became the emperor's vassal and "swore fidelity to him", promising that he would never attack the emperor's realm.