After the Saxon resistance was broken in 804, Charlemagne delegated the administration of the Nordalbingian areas of Saxony to his allied Slavic neighbors, the Obotrites. But when the Danish Vikings strengthened under King Godfred, Charlemagne tasked the Frankish Earl Egbert with securing the border. In 810 Egbert built Esesfelth Castle on the western outskirts of the present-day town Itzehoe as the first Frankish fortification north of the Elbe. The fort was built in an extremely favorable strategic position. It had a direct connection to the Elbe and the Ox Road (Hærvejen), which was as a military and trade route from Hamburg to Jutland. Military consolidation was soon followed by Christian consolidation as well. Esesfelth became the most important base of the Nordic mission under Ebbo, the influential archbishop of Rheims.