Simplify the following text for a Grade 9 native English-speaking person.
Original: The Thracians and the other auxiliaries who were left in the camp , in total seven cohorts , defended bravely , but they were not able to fend off the enemy assault .
Simplified: The Thracians and the other auxiliaries who were left in the camp defended bravely , but they were not able to fend off the enemy assault .