Why was the hiring of Germanic mercenaries by Western Roman emperors a mistake?

The Germanics were poor soldiers who could not handle Roman weapons.
The Germanics lacked loyalty to Rome and sometimes fought against the empire.
The regular Roman army rose up against the mercenaries and killed many of them.
The regular Roman army joined with the mercenaries to attack the Eastern Roman Empire.

Question

Why was the hiring of Germanic mercenaries by Western Roman emperors a mistake?

The Germanics were poor soldiers who could not handle Roman weapons.
 The Germanics lacked loyalty to Rome and sometimes fought against the empire.
 The regular Roman army rose up against the mercenaries and killed many of them.
 The regular Roman army joined with the mercenaries to attack the Eastern Roman Empire.

justus · Answer

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