Alans, nomadic pastoralists who lived in the northern Pontus in the early cents. ce, operating politically in a number of separate subgroups. They often tried to cross the Caucasus—Arrian, when governor of Cappadocia, beat off one such attack—but Roman emperors from Nero onwards fortified the region's western exits against them. In the late 4th cent., the Huns overran their territory, conquering some groups, and driving others westwards. These crossed the Rhine on 31 December 406, some subsequently being absorbed into the Hasding Vandal monarchy in Spain, others reaching accommodations with the Roman state in Gaul.