Rivers and sea lanes held the Roman Empire together

The Mediterranean served as an internal line of communication, so neglecting naval defence threatened access to imperial territory and resources. Elliott connects British Roman forts to navigable rivers and the road network, showing how land and water transport reinforced one another. He lists Exeter, Gloucester, Cardiff, Chester, Leicester, Manchester, York, Newcastle, and Carlisle as modern settlements rooted in riverside Roman forts. Roads tied those nodes together, but the fastest route from Rome to Londinium ran from Ostia largely by sea and river through Marseille, the Rhône-Saône corridor, Boulogne, and Richborough or Dover. A message could arrive in roughly eleven or twelve days precisely because most of the journey used water.