The Roman Empire was defeated by its own internal problems, as well as by its inability to defend itself from outside threats. These internal problems included:
1) A growing gap between rich and poor citizens led to political instability within Rome itself, which caused many citizens to leave Rome for other parts of Europe where they could enjoy more freedom and equality with other citizens.
2) The Romans had become weak due to their constant fighting with other nations such as Carthage and Greece; both wars had left them exhausted and unable to defend themselves against outside threats.
3) The Romans did not have enough manpower left in their army after these wars, so they resorted to hiring foreign mercenaries (e.g., Goths) who turned against them when they were no longer needed or paid;
Also, the Roman Empire was defeated by the Germanic tribes in 476 A.D., when Emperor Romulus Augustus was removed from power. This defeat marked the end of the western Roman Empire and the beginning of Europe’s Middle Ages.
The Germanic tribes were led by their King Odoacer (or Odovacar). He was an Ostrogoth leader who deposed Emperor Romulus Augustus and ruled over Italy for 17 years. His reign ended when he was killed by Theodoric’s forces in 493 A.D., which resulted in Italy being ruled again by an Ostrogoth king named Theodoric II until 526 A.D..