The Neptune Association

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
PART 2      a) DELAYED REPORTS
An Italian press report states that over 1800 British prisoners have been rescued from the VENIERO, which was torpedoed and subsequently beached near NAVARINO. Cruiser CADORNA with 920 (British) prisoners has probably arrived back at TARANTO from Benghazi.
PART 3     FUTURE MOVEMENTS
On Sunday 14th ANKARA, PISANI, MONGINEVRO and NAPOLI sail for Benghazi, while at the same time the FILSI and DEL GRECO sail for Tripoli. The escort and screening force comprises 4 battleships, 6 cruisers and 25 destroyers.

December 15th 1941
PART 2      a) DELAYED REPORTS
CAPO ORSO and ISEO have both returned to ARGOSTOLI with serious leaks. CAPO ORSO has had to be beached. (The 2 merchant ships that collided on 13th.)

 December 16th 1941
PART 1 AT SEA      a) SOUTHBOUND
There are indications that a second attempt may be made to run ships through to N. Africa, starting possibly today 16th. Ships available are (probably) ANKARA, PISANI, MONGINEVRO and NAPOLI, destined for Benghazi, and FILSI and DEL GRECO which were originally destined for Tripoli.
Destroyer PIGAFETTA sailed from Taranto at 0830/15 with a cargo of aviation spirit for Benghazi. Speed 18 knots. Due to arrive 1000/16.

Ultra signal 16 Dec 1941

 

December 17th 1941
PART 1 AT SEA      a) SOUTHBOUND
ANKARA (4770), escorted by destroyer SAETTA and one other. PISANI (6400), MONGINEVRO (5500) and NAPOLI (5450) escorted by destroyer VIVALDI and five others were to leave Taranto about noon/16. The first named is due Benghazi 0800/18 and the rest Tripoli at 1700/18.

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.

Ultra signal 17 Dec 1941

 

December 18th 1941
PART 1 AT SEA      a) SOUTHBOUND
ANKARA (4770), PISANI (6400), MONGINEVRO (5500) and NAPOLI (5450) sailed from Taranto 1300/16. They were sighted at 1625/17 by aircraft and were being escorted by 2 battleships, 2 cruisers and 12 destroyers. A supporting force of 3 battleships, 2 cruisers and 10 destroyers was to the northeastward. After our forces made contact LITTORIO was told he could alter the routes of the convoys as necessary. At dawn/18 PISANI convoy was 5 hours behind schedule.

Ultra signal 18 December 1941 (page 1)

 

PART 2 LATE REPORTS
Destroyer PIGAFETTA with 200 British prisoners should have arrived at SUDA at 1200/17. At 1800/17 Rome had asked Salonika and Patras for news of PIGAFETTA and Patras replied at 2020/17 that she was not at any port in his command.

Ultra signal 18 December 1941 (page 2)

 

December 19th 1941
PART 1 AT SEA      a) SOUTHBOUND
At 1300/18 when in position 33 deg 18’ N: 15 (?) deg 33’ E the convoy broke up into 2 parts, ANKARA and 2 destroyers proceeding to Benghazi, and the PISANI, MONGINEVRO and NAPOLI escorted by 3 cruisers to Tripoli. At 1400 the main supporting force started back for Taranto and soon after dark the escorting cruisers also left for their base.
NAPOLI was damaged by air attack, putting her rudder out of action. Convoy is to enter harbour this morning after sweeping has taken place, owing to the probability of magnetic mines having been dropped.

PART 2 LATE REPORTS
Destroyer PIGAFETTA which was due at SUDA at 1200/17 from BENGHAZI with 200 British prisoners, was delayed by engine trouble.

Ultra signal 19 December 1941

 

December 20th 1941
PART 2 LATE REPORTS
Submarines BRAGADINO and MOCENIGO were due off Benghazi early this morning 20/12.
PISANI (6400) and MONGINEVRO (5500) escort VIVIALDI and DI ROCCO arrived at Tripoli 1015/19. Destroyers ZERO, PESSAGE, DA NOLI and MALOCELLO arrived at 1400/19 and the NAPOLI (5450) who had been damaged by torpedo aircraft, escorted by RTB’s arrived 1600/19.
PART 3 FUTURE MOVEMENTS
Submarine VENIERO is due off Benghazi tomorrow evening 21/12
SPEZIA (1600) and CADAMOSTO (1000) are due to leave Tripoli in ballast at 1600 today Dec 20 for Benghazi.

Ultra signal 20 Dec 1941

 

 

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