The First World War barrage suggested a defensive model that Britain tried to revisit as France collapsed in 1940. Holding Calais or Cherbourg might have preserved controlled cross-Channel access and supported a renewed barrier system. An interwar hydrophone network on the English side could have monitored submarines and surface traffic while sharing data with France. Its absence illustrates how the belief that the Great War had ended major war allowed specialized surveillance knowledge and infrastructure to lapse.
Notable Point · 9:44-11:17
The lost interwar surveillance opportunity in the Channel
Britain considered recreating Channel barriers around Calais and Cherbourg in 1940, but had not preserved a peacetime hydrophone network that could have supported them.