Carausius turns naval expertise into a breakaway sea empire

Carausius was chosen to fight Germanic raiders because he combined extensive land command with experience leading naval units in the Rhine delta. He succeeded against the pirates, but imperial jealousy and an attempted purge helped turn that successful commander into a usurper. Maritime power then allowed his breakaway regime to exclude the imperial center from Britain and the North Sea for years. As his fleet was worn down, Carausius developed parts of the Saxon Shore fort system, including positions associated with Richborough, Dover, Pevensey, and Portchester. Elliott argues that fixed forts could catch raiders mainly on withdrawal and required heavy continuing expense, whereas a fleet in being could deter, intercept, and maneuver before an attack reached shore.