By the 4th cent. the Visigoths were at the borders of the East Roman Empire, raiding across the Danube River, and peacefully infiltrating the trans-Danubian provinces. Constantine I was troubled by the Visigoths, but they became a real menace only after the middle of the 4th cent. At that time groups of Visigoths had settled in Dacia as agriculturalists, and many had accepted Arian Christianity (see Arianism), partly as a result of the work of Ulfilas. About 364 a group of Visigoths devastated Thrace, and punitive measures were undertaken against them. They were also involved in the revolt (366) of Procopius.
Until 369 Emperor Valens waged war successfully against the Visigoths, who were led by Athanaric. Athanaric asserted his supremacy over Fritigern, a rival Visigothic leader who then retired into the Roman Empire and obtained Roman aid against Athanaric. However, the internal affairs of the Goths became of secondary importance to the invasion (c.375) of their lands by the Huns. Athanaric retired to Transylvania, and the majority of the Visigoths joined Fritigern and fled (376) into the empire. Subjected to oppressive measures by Roman officials, these Visigothic settlers soon rose in revolt. Opposed by Emperor Valens at Adrianople in 378, the Goths won a decisive victory. They then swept across the upper Balkan Peninsula and ravaged Thrace. Theodosius I immediately took up arms against them. In 382 peace was finally concluded, and the Goths under Athanaric were settled in Thrace. Friction, however, continued.
In 395, after the death of Theodosius I, the Visigothic troops in Roman service proclaimed Alaric I their leader; under his strong guidance they first developed the concept of kingship. Alaric led a revolt in the Balkan Peninsula but was checked by Stilicho. In 401 Alaric began his attacks on Italy; he was halted by Stilicho, but after Stilicho's death he succeeded in his invasion, and the Visigoths became masters of Italy. Negotiations between Alaric and Emperor Honorius failed, and in 410 the Visigoths sacked Rome. Alaric died soon afterward.
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