On their first invasion they not only conquered this country but reduced to subjection many of the neighbouring peoples, striking terror into them by their audacity.
Not long afterwards they defeated the Romans and their allies in a pitched battle, and pursuing the fugitives, occupied, three days after the battle, the whole of <a class="linkToPlace" target="_blank" href="/place?placename=Rome&groupId=935&placeId=1669">Rome</a> with the exception of the Capitol,
but being diverted by an invasion of their own country by the Veneti, they made on this occasion a treaty with the Romans, and evacuating the city, returned home.
After this they were occupied by domestic wars, and certain of the neighbouring Alpine tribes, witnessing to with prosperity they had attained in comparison with themselves, frequently gathered to attack them.
Meanwhile the Romans re-established their power and again became masters of <a class="linkToPlace" target="_blank" href="/place?placename=Latium&groupId=673&placeId=1231">Latium</a>.
Thirty years after the occupation of <a class="linkToPlace" target="_blank" href="/place?placename=Rome&groupId=935&placeId=1669">Rome</a>, the Celts again appeared before Alba with a large army, and the Romans on this occasion did not venture to meet them in the field, because, owing to the suddenness of the attack, they were taken by surprise and had not had time to anticipate it by collecting the forces of their allies.
But when, twelve years later, the Celts again invaded in great strength, they had early word of it, and, assembling their allies, marched eagerly to meet them, wishing for nothing better than a decisive battle.
The Gauls, alarmed by the Roman advance and at variance among themselves, waited until nightfall and then set off for home, their retreat resembling a flight.
After this panic, they kept quiet for thirteen years, and then, as they saw how rapidly the power of the Romans was growing, they made a formal peace with them, to the terms of which they adhered steadfastly for thirty years.
Walbank Commentary