ermanus of Auxerre is known in particular for his evangelisation among the Britains converted to the Pelagian heresy.
A synod called at the instigation of pope Celestine I (422-432) decided to send missionaries to combat this error. Germanus made two journeys to restore the Britons to Catholic orthodoxy, the first in 429, the second in 431.
His weapons included his persuasive preaching, the example of his austere life and the accomplishment of several miracles, including the healing of a young blind girl.
While the bishop obtained numerous conversions, the Britons were menaced by the incursions of the Picts and the Saxons into their territory. Germanus took command of the newly baptised troops, enjoining them to take up their resolve with fortitude. The shouting of a hallelujah three times by the Britons assembled in order of battle resulted in the rout of the aggressors.
During his first journey to Britain, Germanus stopped to preach at Nanterre.
There, among the crowd, he spurred the vocation of Geneviève, still a little girl, to serve Christ and helped to lead her in this path.