In the 4th century, Huns tribe from Asia attack Germanic tribe and kill them fiercely.
Germanic tribe people come and ask to stay in Constantinople and they will fight in the battle for Romans in return. In 378 A.D. at the war in Adrianople, Visigoth tribe win over Romans and get Dacia state as their headquarter. In 391 A.D. Theodosius the emperor sets the law to make Christianity as the only one religion in Roman empire. The belief according to the religion, it heals all the thirst of war of the Romans. It makes the Romans have to hire Germanic tribe to fight for them in the battle with Germanic tribe. This also makes Romans
weak. Theodosius the emperor cuts Roman empire into two parts, the west and the east. Cutting it is like cutting a tumor. The west is destroy by the invasion of Barbarians, make the east still powerful and rich with silk road trading and still survive for another thousand year. In 409 A.D. Vandal tribe can’t fight the Huns anymore, they cross Rhine river that is ice to Gaul state and raid all the way, they settle at Iberia peninsula. In 410 A.D. Alaric of Visigoth and his soldier attack Rome, burn and destroy the city, that make Honorius the emperor of the west give them Aguitan state. In 429 A.D. Visigoth tribe leave Aguitan and attack Vandal tribe in Iberia and vanish them to north Africa. In 455 A.D. Vandal tribe bring ship from Africa to attack Rome In 476 A.D. Odoacer of Germanic tribe attack Rome and depose the last emperor of the west, Romulus Augustus. So the east send Theodoric of Ostragoth tribe to take back Rome. But he set his own kingdom instead. Rome has many problems. This weakened the Roman empire, such as the weak economy, higher taxation, the agricultural area was destroyed by the battle. Technology not updated and the Empire had to fight wars often including political issues. The Roman empire was very weak. Until the German ancestors invaded the Roman empire.