OPERATIONS INTELLIGENCE CENTRE SPECIAL INTELLIGENCE SUMMARIES
ITALIAN CONVOY SITUATION (13 to 20 December 1941)
(Notes in italics by John McGregor)
The Italian C38m Enigma code was first decrypted at Bletchley Park in June 1941. By December, the decryption of Italian Naval radio traffic was so efficient that there was a delay of just 7 hours between an ENIGMA message being transmitted by Admiralty Rome and an ‘F’ (for Foreign) telegram of the contents or implications thereof being sent by the Deputy Director of the Operational Intelligence Centre at the Admiralty to the relevant foreign station authority such as Vice Admiral Malta. A daily 'Special Intelligence Summary' of such telegrams (including intelligence from other sources)was prepared each evening for circulation to senior Naval Staff (and Army and Air Staff Intelligence Chiefs) in London. The cut off for the latter appears to have been around 6pm.
These extracts relevant to the Neptune tragedy are copied from ULTRA Special Intelligence Summaries dated 13th to 20th December 1941, decrypted at Bletchley Park from intercepted messages in the Italian ENIGMA code and prepared by the Operational Intelligence Centre in London. These Summaries and the F series telegrams are held in the National Archives at Kew and examples are shown for relevant dates. (click on summary for full screen)
On December 13th, 8 fully laden merchant ships sailed from Italy for Libya escorted by most of the Italian fleet. That night the British submarine Upright sank 2 merchant ships Fabio Filsi and Carlo del Greco and the British submarine Urge put a torpedo into the Battleship Vittorio Veneto. In the chaos that followed, 2 more merchant ships collided and the convoy reversed course and retreated to Italy. No fewer than 5 British submarines were in place to intercept the convoy thanks to Enigma decrypts. At the highest level the convoy was ordered to try again and they set sail on 16th with the 4 remaining merchant ships (Ankara, Pisani, Monginevro and Napoli). For several days the convoy situation had been very closely monitored by Vice Admiral Malta. The vital telegram received about 1700 on 18th prompted him to summon Captain O'Conor and despatch Neptune and all available ships to intercept the convoy bound for Tripoli. After refuelling they sailed at 1800.
The crucial part played by ENIGMA decrypts in the naval war is demonstrated very clearly. The submarines could not have been deployed so effectively and the convoy could not have been monitored without ENIGMA. Conversely the difficulty in keeping it secret must have been extremely difficult for the tiny handful of officers cleared to read ULTRA signals. The fact that Bletchley had read the ENIGMA code was not made public until 1975.
Another matter of deep concern to Vice Admiral Malta was the transport of British POW's from Libya to Italy. To avoid compromising ENIGMA, Winston Churchill had edicted that although we knew from the transcripts that some of the Italian ships were carrying POW's we couldn't just not sink those ships in case it gave a clue that the code had been cracked. Our submarines or aircraft were sent to the convoy positions without knowing that POW's were on board. The transcript of 13 December refers to the Italian ship Sebastiano Veniero that had been torpedoed on 9th December by the British submarine Porpoise, carrying over 2000 British POW's of whom 1800 were saved. In all 312 POW's died. Between October 1941 and November 1942, six Italian ships carrying POW's were sunk by British submarines before the policy was rescinded.
December 13th 1941
December 15th 1941
December 16th 1941
December 17th 1941
The convoy will be supported by the battleship DUILIO and the 7th cruiser division (probably 6” cruisers AOSTA and ATTENDOLO).
It is possible other forces including the battleship LITTORIO may be at sea.
December 18th 1941
PART 2 LATE REPORTS
December 19th 1941
PART 2 LATE REPORTS
December 20th 1941
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