I want to know the answer to the following question:
How many of the Roman military were involved in the Battle of Allia River?
All the background I'm provided with is that "The Gauls, led by chieftain Brennus, defeated the Roman army of approximately 15,000 troops, pursued the fleeing Romans back to Rome, and sacked the city before being either driven off or bought off.". Is that enough to answer the question?