The Italians did not pass on the full code to the Chiffrierabteilung, their German counterparts, only providing limited information such as decoded American messages.
Information from Fellers' messages alerted the Axis to British convoy operations in the Mediterranean Sea, including efforts to resupply the garrison of Malta.
Beginning in January 1942 information about the numbers and condition of British forces was provided to General Erwin Rommel, the German commander in Africa.
[4] But some, like Colonel Alfred McCormack, were unconvinced and suspected that the British were reading the dispatches in the American "Black" code, not the Germans.
McCormack finally concluded that was not the case, but considerable ill feeling had been aroused (Churchill had told Roosevelt in February 1942 that he had stopped British work on American diplomatic codes, a warning to tighten them up).