Following Galerius' recognition of Constantine as caesar, Constantine's portrait was brought to Rome, as was customary. Maxentius mocked the portrait's subject as the son of a harlot and lamented his own powerlessness. Maxentius, envious of Constantine's authority, seized the title of emperor on 28 October AD 306. Galerius refused to recognize him but failed to unseat him. Galerius sent Severus against Maxentius, but during the campaign, Severus' armies, previously under command of Maxentius' father Maximian, defected, and Severus was seized and imprisoned. Maximian, brought out of retirement by his son's rebellion, left for Gaul to confer with Constantine in late AD 307. He offered to marry his daughter Fausta to Constantine and elevate him to augustan rank. In return, Constantine would reaffirm the old family alliance between Maximian and Constantius and offer support to Maxentius' cause in Italy. Constantine accepted and married Fausta in Trier in late summer AD 307. Constantine now gave Maxentius his meagre support, offering Maxentius political recognition.