 In 310 , Maximian rebelled against Constantine while the Emperor was on campaign against the Franks . Maximian had been sent south to Arles with part of Constantine 's army to defend against attacks by Maxentius in southern Gaul . In Arles , Maximian announced that Constantine was dead and took up the imperial purple . Although Maximian offered bribes to all who would support him , most of Constantine 's army remained loyal , and Maximian was compelled to leave the city . Constantine soon heard of the rebellion , abandoned his campaign against the Franks , and moved quickly to southern Gaul , where he confronted the fleeing Maximian at Massilia ( Marseille ) . The town was better able to withstand a long siege than Arles , but it made little difference as loyal citizens opened the rear gates to Constantine . Maximian was captured , reproved for his crimes , and stripped of his title for the third and last time . Constantine granted Maximian some clemency but strongly encouraged his suicide . In July 310 , Maximian hanged himself . 
