Excerpts from Books and Wikipedia
Atilla, king of the Huns (r.434-453), invaded the Western Empire just 2 years before he died. Opposing Attila was Aetius, a Roman master general. "Attila's invasion was as much a threat to these German settlers as it was to the Romans, enabling Aetius to build an unlikely coalition of his frontier enemies." [Furtado: 1001 Days] "A nomadic people from Mongolia, the Huns became a formidable force from as early as the 3rd century BCE. . . . These superbly skilled horsemen lived and fought in the saddle, covering great distances across the barren steppes of Central Asia. . . . The Huns continual raids across the borders of Han China, prompted the Chinese to build the Great Wall . . . From about 350 CE, the Huns began to move westward, invading southern Russia, India, and the Sassanian Empire. . . . Their arrival in West in the late fourth century precipitated a major crisis. They overran Ostrogothic territory, defeated the Alans, and then turned on the Visigoths. These barbarian groups turned to Rome for protection. Entering the Empire as that federati (Confederates), they served against other barbarians under the command of their own chiefs. The last great Hunnish assault on the West, in 440, all but delivered the final coup de grace to the Roman Empire." [DK Timeline, p. 96]