 Constantine 's advisers and generals cautioned against preemptive attack on Maxentius ; even his soothsayers recommended against it , stating that the sacrifices had produced unfavorable omens . Constantine , with a spirit that left a deep impression on his followers , inspiring some to believe that he had some form of supernatural guidance , ignored all these cautions . Early in the spring of 312 AD , Constantine crossed the Cottian Alps with a quarter of his army , a force numbering about 40 @,@ 000 . The first town his army encountered was Segusium ( Susa , Italy ) , a heavily fortified town that shut its gates to him . Constantine ordered his men to set fire to its gates and scale its walls . He took the town quickly . Constantine ordered his troops not to loot the town , and advanced with them into northern Italy . 
