In 390-387 bce, rome was threatened by an invasion of northern italy by the

In 390 BCE the Gauls under their leader Brennus attacked Rome. In the battle of Allia 390 BCE Gauls defeated Roman army. After that they attacked the city of Rome. The Romans retreated to the Capitoline and watched the destruction of their city. The Gauls burned Rome and left only after being payed 1,000 libres in gold.
An invasion by the Gauls.