The means by which the Anglo-Saxons marshalled forces to defend against marauders also left them vulnerable to the Vikings. It was the responsibility of the shire fyrd to deal with local raids. The king could call up the national militia to defend the kingdom but in the case of the Viking raids, problems with communication and raising supplies meant that the national militia could not be mustered quickly enough. It was only after the raids had begun that a call went out to landowners to gather their men for battle. Large regions could be devastated before the fyrd could assemble and arrive. Although the landowners were obliged to the king to supply these men when called, during the attacks in 878 many of them abandoned their king and collaborated with Guthrum.