The battle took place in the vicinity of Adrianople, in the Roman province of Thracia (modern Edirne in European Turkey).

[8] As part of the Gothic War of 376–382, the battle is often considered the start of the events which led to the fall of the Western Roman Empire in the 5th century.

A detailed contemporary account of the lead-up to the battle from the Roman perspective was written by Ammianus Marcellinus and forms the culminating point at the end of his history.

[9] In 376, the Goths, led by Alavivus and Fritigern, asked to be allowed to settle in the Eastern Roman Empire after being displaced by the invasions of the Huns.

Hoping that they would become farmers and soldiers, the Eastern Roman emperor Valens allowed them to establish themselves in the Empire as allies (foederati).

[10] In 378, Valens decided to take control himself and assembled additional troops from his own resources in Syria and from the reserves of the Western Roman Empire in Gaul.

Fritigern as the leader of the Goths assembled his forces at Nicopolis and Beroe (now Stara Zagora) in order to deal with the Roman threat.

[15] Richomeres, sent in advance to Adrianople by Gratian, carried a letter asking Valens to wait for his arrival with reinforcements before engaging in battle.

[citation needed] However, some modern historians estimated the real number of Roman troops to be as many as 15,000 men, 10,000 infantry and 5,000 cavalry.

[22] More recent scholarly works mostly agree that the armies were similarly sized, that the Gothic infantry was more decisive than their cavalry and that neither the Romans nor the Goths used stirrups until the 6th century,[23] probably brought by the Avars.

[15] This appears to be due to Alatheus and Saphrax's forces being away when the Roman scouts estimated the Goths' numbers before battle.

Three possible locations of the battle have been discussed in modern historiography: On the morning of 9 August, Valens decamped from Adrianople, where he left the imperial treasury and administration under guard.

The negotiations exasperated the Roman soldiers who seemed to hold the stronger position, but they gained precious time for Fritigern.

Some Roman units began the battle without orders to do so, believing they would have an easy victory, and perhaps over-eager to exact revenge on the Goths after two years of unchecked devastation throughout the Balkans.

The imperial scholae of shield-archers under the command of the Iberian prince Bacurius attacked, but lacking support they were easily pushed back.

An alternative story circulated after the battle that Valens had escaped the field with a bodyguard and some eunuchs and hid in a peasant's cottage.

Many officers, among them the general Sebastianus, were killed in the worst Roman defeat since the Battle of Edessa, the low point of the Crisis of the Third Century.

Despite the losses, the Battle of Adrianople did not mark the end of the Roman Empire because the imperial military power was only temporarily crippled.

Charles Oman in 1960 wrote that the battle represented a turning point in military history, with heavy cavalry triumphing over Roman infantry and ushering in the age of the medieval knight.