 In early 288 , Maximian appointed his praetorian prefect Constantius Chlorus , husband of Maximian 's daughter Theodora , to lead a campaign against Carausius ' Frankish allies . These Franks controlled the Rhine estuaries , thwarting sea @-@ attacks against Carausius . Constantius moved north through their territory , wreaking havoc , and reaching the North Sea . The Franks sued for peace and in the subsequent settlement Maximian reinstated the deposed Frankish king Gennobaudes . Gennobaudes became Maximian 's vassal and , with lesser Frankish chiefs in turn swearing loyalty to Gennobaudes , Roman regional dominance was assured . 
