So the Celts on their part began the war, either because the Roman assignations of land on the east coast (522), although not a measure immediately directed against them, made them apprehensive of danger; or because they perceived that a war with Rome for the possession of Lombardy was inevitable; or, as is perhaps most probable, because their Celtic impatience was once more weary of inaction and preferred to arm for a new warlike expedition.

With the exception of the Cenomani, who acted with the Veneti and declared for the Romans, all the Italian Celts concurred in the war, and they were joined by the Celts of the upper valley of the Rhone, or rather by a number of adventurers belonging to them, under the leaders Concolitanus and Aneroestus.( 15) With 50,000 warriors on foot, and 20,000 on horseback or in chariots, the leaders of the Celts advanced to the Apennines (529).

The Romans had not anticipated an attack on this side, and had not expected that the Celts, disregarding the Roman fortresses on the east coast and the protection of their own kinsmen, would venture to advance directly against the capital.

Not very long before a similar Celtic swarm had in an exactly similar way overrun Greece.

The danger was serious, and appeared still more serious than it really was.