italy had traditionally been exempt from any form of taxation, but galerius ignored this. italy began to murmur against this indignity and maxentius used this sentiment to declare himself emperor in italy, to the fury of galerius. therefore, galerius ordered his colleague severus to immediately march to rome, so that, by his unexpected arrival, he would easily suppress the rebellion. severus was quickly captured and executed by maximian, who had once again been elevated to the rank of co-emperor, this time by his son maxentius.