The Atacati and the Barbarians

In 401, Alaric marched into Italy unchallenged and had a field day. Despite that he did a good job of turning the barbarian horde, Silico was still trapped on the wrong side of the Alps. So chances are that the island was pretty largely looted of what soldiers remained as well as any potential recruits. In fact, it seems that even the Atacati were called up during this period.