“The first casualty in War is the Truth”
Some German naval records relating to the Kormoran fell into British hands at the end of the war in Europe and are now in the UK Public Record Office at Kew. With them are related Admiralty documents, and one such Secret file, downgraded to Confidential on 6.1.1946, is ADM 1/18899 including NID 06923/45, now available for researchers. These provide some interesting details but certainly not a complete picture of the raider’s activities, as it was well before the Ultra and Signal Intelligence revelations. Each side had some significant SIGINT successes against the other, with the Germans having a distinct edge on us in the first half of the war. Inexplicably, each of the main antagonists was `head in the sand’ concerning its own communication security, often failing to detect or even suspect that the enemy was also reading some of their codes and ciphers, etc. (It was in the `unthinkable’ category, and the Japanese fell into the same false sense of security later.)
So, some of the best kept war secrets were not necessarily one’s own cryptographic systems but the very least hint that an enemy cipher machine had been captured, code broken, or otherwise compromised. The circumstances of many of these compromises were so sensitive that such records and details were kept to a bare minimum. On the German side a basic security directive strictly limiting distribution was issued by Hitler personally, so it is unlikely that some secrets would find their way into postwar archives.
One German disclosure on the above NID file and 06978/45 is that a British signal of 26.11.41, deciphered on 30.11.41, reported that Sydney was overdue and that some German survivors had been taken aboard a British tanker (Trocas) from a rubber dinghy and others had landed on the WA coast. Due to shell damage to her wireless offices and antennas Kormoran had been unable to transmit any report of the action to HQ. But, with such effective intelligence gathering, one author has observed that the German authorities appeared to have been almost as well informed as the Australian Naval Board (ACNB).
The analysis of Captain Detmer’s book (‘The Raider Kormoran’ in N.H. Review, Sept. ’99) gives a fair idea of how well briefed and provided for they were before departure and during subsequent rendezvous with other raiders and supply ships. He makes bare mention of the stream of intelligence provided by HQ from decrypted allied signals, etc, although he rather inadvertently reveals the effectiveness of his own ship’s team of intercept operators.
Also on file is a secret RAN report of 12 Feb 1942 to the Admiralty, following further interrogation of the German crew, including a breakdown of the Kormoran’s `extensive’ communication complement. Besides an officer and a yeoman there was a chief, 3 watch supervisors and 18 wireless operators. Allowing for the regular communication watch with base, a very occasional operator to join a prize crew and perhaps a few acting as visual signalmen at action stations, it left a significant effort `to monitor the air waves’ for intelligence purposes. Flag signalling was apparently left to seamen, under the yeoman’s tuition, to put on a `star’ performance of inept flag handling in a typical `merchant ship’.
One of the raider’s spectacular coups was the sinking of two British ships in mid Atlantic on 29 January 1941. The large Afric Star was actually surprised by the Kormoran and abandoned before she could be scuttled and secret books destroyed, but due to her size and damage Detmers decided not to try and send her back to Germany. Classified publications taken intact by the German boarding party included the `Merchant Ship Code with a complete bigramme table 7 and other documents as well, evidently including some callsign material. It was put to good use immediately, as within three-and-a-half hours a second ship was sunk after dark and the compromised British codes confirmed her name as Eurylochus! The raiders Atlantis and Pinguin captured further merchant ship cryptographic material in April 1941.
Unique war callsigns were issued to individual British Commonwealth merchant ships in sealed Secret Envelopes `Z’, to be opened only when war broke out. In December 1940 the Admiralty adapted these secret callsigns for a visual challenge and reply system to confirm true identity of Allied ships and unmask enemy vessels which may be posing as friendly merchantmen on the high seas. Dutch ships were not `admitted to the club’ until 1 June 1941 with the issue of their secret callsigns. A coincidence perhaps, but it was soon after this that Kormoran adopted Straat Malakka’s identity in July 1941 and in October Detmers was delighted to receive confirmation from the German Naval Attache in Tokyo of her presence in the Indian Ocean. It is unlikely that Dutch callsigns were revealed by the material captured by the raiders in January and April 1941 as they did not come into force for a further few months, but some dormant allocations may have been listed ready for activation on the effective date. In any case callsign compromises were just as likely to occur through operator or procedural errors such as successive signals linking a ship’s plain international callsign with a secret one, which is the type of thing that the Kormoran’s eavesdroppers would have been trained to watch for. Raiders gained further details by challenging their merchant vessel victims and noting their responses. There were also espionage opportunities such as when allied merchantmen with German wireless equipment installed had it serviced in neutral ports (in radio offices where simple key safes contained their codes and callsigns). Specific cases are unlikely ever to be revealed but, suffice to say that the Official RN Historian records, after the publication of his works, that some allied merchant ship secret callsigns were held by the Germans. (Roskill Papers in the Churchill Archives Centre, Churchill College, Cambridge, UK). There is further evidence of this below, following the Sydney/Kormoran engagement.