The battle took place in November of 268 between approximately 35,000 men under the command of the Roman Emperor Claudius II Gothicus and the Germanic tribe of the Alamanni, whose invading army may have numbered upwards of 100,000.
The Alamanni, who had been making incursions into Roman territory since the reign of Marcus Aurelius, had broken through the Roman frontier at the Brenner Pass earlier in the year, when internal rebellions and a huge invasion by the Goths forced the Romans to denude the frontier of troops. That fall, when virtually the entire Roman army was busy crushing the Goths at the Battle of Naissus, the Alamanni occupied large areas of undefended northern Italy.
Claudius may well have tried to negotiate a withdrawal by the Alamanni, but when that failed, he chose to fight them instead. Details of the battle are sketchy, but it is known that Claudius won a tremendous victory, killing or captuing more than half the force confronting him, and sending the rest fleeing back over the Alps.
The Roman victory at Lake Benacus, coupled with that won by Gallienus, Claudius and Aurelian at Naissus, provided evidence that the Roman empire could still successfully resist its enemies. The people of the empire took heart from these triumphs, and over the next seven years, Claudius and his brilliant general and successor Aurelian recovered all the empire's lost territories and ejected all the barbarian invaders.