River Somme
The garrisons of the camps were composed of infantry and several cavalry regiments. Monitoring and surveillance of the Channel were the responsibility of the "Classis Britannica" and "Classis Sambrica", whose headquarters were in "Locus Quartensis" (Port d'Etaple), guarding the mouth of the River Somme. The units of "comitatenses, limitanei" and "liburnaria" in this area came under the command of three generals: