 Maxentius prepared for the same type of war he had waged against Severus and Galerius : he sat in Rome and prepared for a siege . He still controlled Rome 's praetorian guards , was well @-@ stocked with African grain , and was surrounded on all sides by the seemingly impregnable Aurelian Walls . He ordered all bridges across the Tiber cut , reportedly on the counsel of the gods , and left the rest of central Italy undefended ; Constantine secured that region 's support without challenge . Constantine progressed slowly along the Via <unk> , allowing the weakness of Maxentius to draw his regime further into turmoil . Maxentius ' support continued to weaken : at chariot races on 27 October , the crowd openly taunted Maxentius , shouting that Constantine was invincible . Maxentius , no longer certain that he would emerge from a siege victorious , built a temporary boat bridge across the Tiber in preparation for a field battle against Constantine . On 28 October 312 AD , the sixth anniversary of his reign , he approached the keepers of the Sibylline Books for guidance . The keepers prophesied that , on that very day , " the enemy of the Romans " would die . Maxentius advanced north to meet Constantine in battle . 
