Adrianople, Battle of, August 9, 378 A.D., a crushing defeat of the Roman imperial army under Emperor Valens by hordes of Visigoths led by Fritigern, aided by Ostrogoths and members of other barbarian tribes. Valens and two-thirds of his army, about 40,000 men, were killed when trapped in a double envelopment. The Battle of Adrianople was the first barbarian victory over the Romans within the empire. It was a turning point in the history of warfare, establishing a dominance of cavalry that was to last 1,000 years.
Visigoths, or West Goths, a Germanic group that invaded the Roman Empire in the fourth century A.D..
Rome and the Roman Empire, the most powerful state of the ancient world. It grew from an Italian village to a city-state and into an organization that ruled the shores of the Mediterranean and much of western Europe.