Seaman Briggs’ story simply was too full of holes to hold up to much scrutiny. For one thing, he could not pin down the circumstances of his intercept of the Winds Execute message. In his interview, he said that he had worked the midnight shift from 3 to 4 December.
Such a shift would have begun late on the evening of 3 December, probably 9:00 or 10:00 PM, or even as late as midnight. It would have ended around 5:00 or 6:00 AM on the morning of 4 December. Yet a few pages later in his interview, he says that all transmissions copied by him between 5:00 AM and 1:00 PM on 4 December were missing. This statement suggests that he worked sixteen straight hours across two shifts. Now, it was not unusual for navy intercept operators to work two eight-hour shifts in one day, but they were separated by a break of eight hours.156 In fact, Briggs was working eight-hour shifts at Cheltenham, according to the log he supplied Toland.
Interestingly, for someone who claimed to have copied such an important message, he could recall no details of it. He could not explain at what time he copied the Execute code phrase, how long the transmission was, what station (callsign) sent it, or what frequency he heard it on. Briggs tried to claim that the station was transmitting somewhere between 13 and 15 Megahertz (MHz). Yet this is not near Safford’s claimed frequency of 11 MHz and quite far from the 9 MHz on which the FCC heard the actual broadcast.
Briggs did say he heard the weather broadcast on what he called the “Orange” weather BAMS broadcast. BAMS was an acronym for the Broadcast to Allied Merchant Ships, a broadcast message system intended for all Allied merchant ships. What he really meant to describe what he was monitoring was the MAM. The MAM was a term U.S. Navy operators used to describe the Japanese merchant ship broadcast, which was similar in some ways to the “BAMS” system. One of the distinguishing characteristics of the Japanese system was that the trigraph “MAM” was used often as the general callsign for all Japanese merchant ships. The MAM system was a worldwide broadcast for Japanese merchant ships, which carried encrypted traffic, as well as shipping information such as notice to mariners and weather reports. There may have even been regular transmission of short news programs in Morse sent to the ships.
However, Briggs’ intercept story is contradicted by the Winds instruction messages. The code phrases and words were to be sent in a strict format. If they were to be sent in Morse, they would appear on the overseas commercial news broadcasts and only as a single word sent five times at the beginning and end of the broadcast. If the code phrases, such as HIGASHI NO KAZAME, were to be used, they would appear only in the voice broadcast. Most importantly, there was no provision in the instructions for transmission over the merchant shipping broadcast.
Source: Center for Cryptologic History National Security Agency, 2008
Robert J. Hanyok and David P. Mowry