Operation CRUSADER saw about 8,500 Commonwealth soldiers become prisoners of the Axis forces, in the fighting around Tobruk and during the counter offensive in January. See this older post for a discussion of losses suffered by each side. This post here is based on research around the internet.
In general, as the old line goes, ‘For you [insert nickname here], the war is over!’. In the case of North Africa, this was however not the case for the Commonwealth POW. In order to secure them and relieve the supply situation in North Africa, beginning in December 41 they were shipped off to Italian-controlled territory, either to Italy or to Greece (and thence to Italy, I guess), either on naval units or on homeward bound merchants (the New Zealand Official History has a good account of the situation of the POW at this link – note that Sebastiano Venier is called Jantzen in this account). This could be dangerous, since POW transports were not marked, and since even when ULTRA had given warning to the Royal Navy that a particular transport carried POW, it was likely impossible to warn the submarine commander without risking a breach in the ULTRA secret (e.g. if the submarine commander were to be taken POW himself, and informed his captors about the warning he was given about leaving a particular transport alone).
In consequence, several hundred Commonwealth POW lost their lives during or shortly after the end of Operation CRUSADER and the counter-offensive.
On 9 December, the large mine-laying submarine HM S/M Porpoise (Lt.Cdr. Pizey DSC) attacked Sebastiano Venier, ex-Jason, off Cape Methone. She is so badly damaged she has to be beached and is written off. Around 300 Commonwealth POW died in the attack.
On 14 February 1942 the brand-new HM S/M P.38 (Lt. Hemingway) attacked a small convoy consisting of Italian steamer Ariosto, German Atlas, and escorts Ct Premuda (ex-Yugoslav Dubrovnik) and Tp Polluce. Ariosto was sunk, hit by two torpedoes, and going down after a few hours in the early hours of 15 February, with 138 Commonwealth POW are lost, almost half the contingent.
On 27 February 1942 the most famous of the Malta submarines, HM S/M Upholder (Lt.Cdr. Wanklyn, VC) sinks the old SS Tembien, launched in 1914. 390 out of 468 Commonwealth POW on board died.
In total therefore, over 800 POW are killed in these attacks, or around 10% of the number of POW taken during CRUSADER and the counter-offensive.
All three submarines undertaking the attack were to be lost with all hands during the war. HM S/M Porpoise was to become the last Royal Navy sub to be sunk by the enemy in the Malacca Straits in 1945. HM S/M P.38 was lost on 23 February on the patrol after she sank Ariosto in a counter-attack by Tp Circe. HM S/M Upholder was sunk on 14 April 1942, possibly by Tp Pegaso.
It is of note that Tp Circe, a Spica-class escort destroyer, was already fitted with German S-Geraet active sonar and depth charges (see this older post). She was on a roll in February 1942, sinking HM S/SM Tempest on 13 February, and HM S/M P.38 on 23 February (misidentified as a ‘Unity-class’, presumably U-class), showing quite well the capability of the new equipment. I have reports by the captain of Circe and a member of the German sonar crew, which I have posted at this link.
Many thanks go to Brian who has researched this topic exhaustively, and to Barb Edy, whose father Don of No. 33 Squadron RAF was on the Ariosto as a POW, and suvrived the sinking. An account of her sinking by Don can be found in Don’s book ‘Goon in the Block’, which I would highly recommend.