Roman fleets on the Danube frontier

The upper-Danube Classis Pannonica and lower-Danube Classis Moesica helped sustain a vital Roman frontier. A cargo sent from Rome through the Mediterranean and Black Sea and up the Danube could reach the frontier more quickly and reliably than an equivalent load moved overland. Food, wine, armour and ammunition all depended on that transport capacity. The fleets protected commercial and supply traffic while serving as border patrols and scouting forces. Their presence also gave the authorities information about conditions along the frontier.