Sea power needs a secure base ashore

Edward's decisive advantage was access to naval strength from the Cinque Ports and other facilities. Ships could move and maneuver forces around the Welsh coast more easily than an army could move across difficult country. Troops ashore still required a secure logistics base. Medieval fleets lacked the persistent reach that modern carriers, missiles, and helicopters give naval forces over land. The castle became the hinge between ships at sea and armies operating inland.