The letter also contained a reference to General Eisenhower that was carefully calibrated. By the spring of 1943, Eisenhower was the supreme Allied commander in the Mediterranean, and any letter from a senior British officer discussing Mediterranean operations would naturally be aware of Eisenhower’s role. The reference established the letter’s context without requiring invented details about Eisenhower’s actual plans.
The tone of the letter, according to analyses by historians who have studied the original document, was consistent with the way Nye actually wrote — he apparently contributed to the drafting of the letter personally, which meant it carried his actual voice and style. This was precisely the kind of detail that a German analyst, even one with access to other Nye correspondence, would find reassuring.
The second official letter, from Mountbatten to Admiral of the Fleet Cunningham, was shorter and less substantive. Its primary purpose was to establish Mountbatten’s connection to Martin and to Combined Operations, thereby confirming Martin’s cover story. The sardine reference about Operation Brimstone was a light touch that reinforced the Sardinia message while maintaining the letter’s casual tone. Mountbatten also asked Cunningham to arrange return passage for Martin, which created the impression of a planned ongoing relationship between Martin and Combined Operations.
The combination of the two letters created a mutually reinforcing picture: a senior staff officer was personally sending a communications channel to carry sensitive material, that material touched on the actual targets of a coming campaign, and the person carrying the material was known to and vouched for by senior officers at multiple levels of command.