Father of Constantine the Great, Constantius I became Caesar of Gaul, Spain and Britain from A.D. 293-305. Constantius was a seasoned general by the time he shared the reins of power with Maximian, Galerius and Diocletian. He brought Gaul and Britain under Roman rule again when he put down a rebellion. When Diocletian and Maximianus I abdicated in A.D. 305, he became co-emperor. He died in Britain of natural causes.