 Galerius refused to recognize Maxentius and sent Severus with an army to Rome to depose him . As many of Severus ' soldiers had served under Maximian , and had taken Maxentius ' bribes , most of the army defected to Maxentius . Severus fled to Ravenna , which Maximian besieged . The city was strongly fortified so Maximian offered terms , which Severus accepted . Maximian then seized Severus and took him under guard to a public villa in southern Rome , where he was kept as a hostage . In the autumn of 307 , Galerius led a second force against Maxentius but he again failed to take Rome , and retreated north with his army mostly intact . 
