The Duisburg convoy carried supplies for the Italian army, German forces, and civilian colonists in Libya. British intelligence benefited from German Enigma traffic as well as work on Italian naval codes. Italian caution about compromised communications contrasted with the German confidence that encouraged a large volume of messages. A sudden increase in traffic between particular headquarters and units could reveal preparations before every message was read. That combination helped the British position surface ships and submarines along a likely route.
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Enigma, traffic analysis, and the Duisburg convoy
Message content and changes in communication volume helped the British anticipate Axis convoy movements.