The historian Ammianus Marcellinus, source of the only detailed version of the battle, says some Roman princes advised Valens not to wait for Gratian, because if Gratian fought Valens would have to share the glory of victory. So on that August day Valens, thinking his troops more than equal to the reported troop numbers of the Goths, led the Roman imperial army into battle.
Roman and Gothic soldiers met each other in a crowded, confused, and very bloody line of battle.
"Our left wing had advanced actually up to the wagons, with the intent to push on still further if they were properly supported; but they were deserted by the rest of the cavalry, and so pressed upon by the superior numbers of the enemy, that they were overwhelmed and beaten down.... And by this time such clouds of dust arose that it was scarcely possible to see the sky, which resounded with horrible cries; and in consequence, the darts, which were bearing death on every side, reached their mark, and fell with deadly effect, because no one could see them beforehand so as to guard against them."Amid the fighting, an additional contingent of Gothic troops arrived, far outnumbering the distressed Roman troops. Gothic victory was assured.
- Ammianus Marcellinus: The Battle of Hadrianopolis
Death of ValensTwo-thirds of the Eastern army were killed, according to Ammianus, putting an end to 16 divisions. Valens was among the casualties. While, like most of the details of the battle, the details of Valens' demise are not known with any certainty, it is thought that Valens was either killed towards the end of the battle or wounded, escaped to a nearby farm, and there was burned to death by Gothic marauders. A supposed survivor brought the story to the Romans.
So momentous and disastrous was the Battle of Adrianople that Ammianus Marcellinus called it "the beginning of evils for the Roman empire then and thereafter."
It is worth noting that this catastrophic Roman defeat occurred in the Eastern Empire. Despite this fact, and the fact that among the precipitating factors for the fall of Rome, barbarian invasions must rank very high, the fall of Rome, barely a century later, in A.D. 476, did not occur within the Eastern Empire.
The next emperor in the East was Theodosius I who conducted clean up operations for 3 years before concluding a peace treaty with the Goths. See Accession of Theodosius the Great.
*Adrianople is now Edirne, in European Turkey. See Roman Empire Map section He.
**The name of the Alamanni is still used by the French for Germany -- L'Allemagne.
De Imperatoribus Romanis Valens
(campus.northpark.edu/history/WebChron/Mediterranean/Adrianople.html) Map of the Battle of Adrianople