Warmatrix

Adrianople (modern day Edirne) has been the site of many battles, named by John Keegan as the most contested spot on the globe. This is because it lies in the center of Thrace, between the Rhodope mountains and the Black Sea. It is the gateway from the northwest to Byzantium a.k.a. Constantinople a.k.a. Istanbul. An important fight that took place here was the battle of 378 CE between the Eastern Roman empire and the Visigoths. It was part of the Gothic War, which lasted several years.
The Goths, a confederacy of tribes who had been pushed westward by the expansion of the Huns, in 376 CE asked permission of the Roman emperor Valens to settle south of the Danube river, inside Roman borders. This was allowed, but the local governors treated them so harshly that they revolted. Their fellow Ostrogoths soon joined them and created a large threat. In 378 CE Valens gathered an army and marched to Adrianople. Confident and in need of victory, he denied both suggestions from his generals to wait for reinforcements and an offer of peace from the Goths. The strength of both armies is very vague. Most modern historians estimate the Roman force at 10,000 infantry and 5,000 cavalry, much less then earlier historians, who went as high as 40,000 in total. The Goths under Fritigern by modern estimates counted 12,000 - 15,000 in total, infantry and cavalry combined.
Valens, who had camped at Adrianople, marched north towards the battlefield through difficult terrain on a hot day. After 7 hours he reached the enemy in the afternoon. His men were tired, thirsty and disordered. The Goths were encamped on a nearby low hill, protected by a triple ring of wagons, a "laager". They burnt the fields, wafting heavy smoke over the legions, and also parlayed, all to win time. The Romans thought they had the advantage and did not want to wait for the night. Some units on the right wing aggressively attacked but were held off by the defenders in front of the camp. In the meanwhile the Roman left wing was still deploying. Then the Gothic cavalry, who had been away foraging, finally arrived from the north. They attacked the Roman cavalry on the right and drove them back; another contingent rode around the camp and did the same on the other flank. The thick smoke prevent the Romans from keeping an overview of the battle. When their flanks collapsed, the Gothic infantry sallied forth from the camp, while the cavalry encircled the enemy. The Romans retreated to the base of the hill. They were trapped and butchered until midnight. Emperor Valens either died on the battlefield or was later burned to death in a cottage where he had fled to.
The Romans lost an emperor, many experienced soldiers (possibly 2/3 of the army) and a string of arms factories. The town of Adrianople withstood a subsequent Gothic attack, but the barbarians did raid Thrace. The battle was a severe blow but not a disaster; neither did it mark the rise of cavalry over infantry, as some historians have claimed. Theodosius, the new emperor of the eastern Roman empire, granted the Goths the right to occupy Thrace if they would swear loyalty to the empire. This marked the beginning of the diffusion of the Romans and barbarians and is the real significance of the battle.