Excerpts from Books and Wikipedia
"The Romans had begun to hear rumors of a new threat: the merciless advance of nomadic enemies from the east, fearless fighters who slaughtered and destroyed, who had no religion, no knowledge of right and wrong, not even a proper language. All the tribes east of the Black Sea were in agitation. . . . Refugees were crowding to the northern side of the Danube, asking to enter the security of Roman territory. The Huns had arrived at the distant edges of the western world." [Bauer: Medieval World, p. 47] "During his reign, he was one of the most feared enemies of the Western and Eastern Roman Empires. He crossed the Danube twice and plundered the Balkans, but was unable to take Constantinople. His unsuccessful campaign in Persia was followed in 441 by an invasion of the Eastern Roman (Byzantine) Empire, the success of which emboldened Attila to invade the West. He also attempted to conquer Roman Gaul (modern France), crossing the Rhine in 451 and marching as far as Aurelianum (Orléans) before being defeated at the Battle of the Catalaunian Plains. He subsequently invaded Italy, devastating the northern provinces, but was unable to take Rome." [Wikipedia]