The open Atlantic deprived patrol lines of the geographical constraints available in the Mediterranean. Convoy avoidance did not depend solely on breaking Enigma: analysts could use the location, volume, and pattern of radio transmissions to infer submarine concentrations. Codebreaking later supplied greater detail, but the less glamorous discipline of traffic analysis already shaped operational routing. Intelligence came from the communications network itself as well as the content of its messages.
Notable Point · 33:16-35:08
Convoy routing exploited radio traffic before codebreaking
Allied traffic analysis could detect concentrations of submarine radio activity and divert convoys even without reading Enigma messages.