 With his newly acquired flotillas , the Flanders Flotilla ′ s commander — Ludwig von Schroeder — decided to launch a raid in the Dover Strait against the Dover Barrage as well as any Allied shipping that could be found in the Channel . Although the British had prohibited transports from being in the Channel at night in anticipation of a German raid , the Dover Barrage was not prepared to meet such an attack . Facing Schroeder ′ s 23 boats , the Dover Barrage was only guarded by the old destroyer HMS Flirt , the yacht Ombra , and the naval trawler H. E. <unk> . The four divisions of drifters manning the barrage ′ s anti @-@ submarine nets were only armed with a single rifle each for defence . In addition to the forces guarding the Barrage , there were six Tribal @-@ class destroyers at Dover that could be called upon in the event of a raid as well as several units of Harwich Force dispersed at the Downs . 
