Simplify the following text for a Grade 12 native English-speaking person.
Original: Although Arminius was ultimately unsuccessful in forging unity among the Germanic tribes , the loss of the Roman legions in the Teutoburg forest had a far-reaching effect on the subsequent history of both the ancient Germanic tribes and on the Roman Empire .
Simplified: Although Arminius could not keep unity among the Germanic tribes , the loss of Roman legions in the Teutoburg forest had a far-reaching effect on the Germanic tribes and the Roman Empire .