Battle of Adrianople

On August 9, 378, at the Battle of Adrianople, a Goth army defeated Roman forces under Emperor Valens. An excerpt from the article:

"The Battle of Adrianople on August 9, 378 CE ranks among the worst military defeats in all of Roman history. Its estimated losses of over 10,000 are comparable to Roman defeats at Cannae (216 BCE) and Carrhae (53 BCE). The battle pitted the Germanic Ostrogoths and Visigoths under the leadership of the Thervingian chieftain Fritigern (d. c. 380 CE) against the unpopular and glory-seeking Roman emperor Valens (r. 364-378 CE). The disastrous defeat exposed Roman military weaknesses which eventually allowed for future barbaric attacks, creating a 'domino effect' that brought about the final decline and fall of the Roman Empire in the west. However, many historians agree that much of the blame for the tragic defeat was due to the poor leadership of Emperor Valens and not the ineptness of the Roman army. In his Roman History, 4th-century CE Roman historian Ammianus Marcellinus said “The annals record no such massacre of a battle except the one at Cannae, although the Romans more than once, deceived by trickery due to an adverse breeze of fortune, yielded for a time to ill success in their wars ....” (481)."