The Sestriere is an object lesson in both the scope and limitations of ULTRA intelligence, showing that comprehensive knowledge alone does not sink ships. Two days before she sailed from Brindisi the British knew that Sestriere was to rendezvous in Greece with another freighter, Valfiorita, then proceed to Africa with a four-strong escort at a speed of 14 knots. ULTRA yielded codenames of their waypoints and timings but those plans went by the board after Valfiorita was torpedoed by Wellingtons of No. 69 Squadron in the Adriatic and towed to Corfu in the early hours of 4 October. Thanks to a thick smoke screen laid by the escorts, the RAF airmen did not know at the time what they had achieved. Pilot Officer Matthews (HX605•L) released his torpedo visually before the smoke had fully covered Valfiorita and when 100 yds beyond her felt a concussion but could only claim a probable hit. Flak meanwhile damaged the Wellington’s main spar and hydraulics and wounded the Special Equipment Operator in the leg. Matthews made a successful crash landing back at Luqa without further injury to the crew.
Later that day it was learned that owing to bottom-fouling Sestriere could achieve no more than 13 kts and that the destroyer Camicia Nera would join Saetta, Pigafetta, and Folgore in escorting her. German wireless operators would be aboard the latter two vessels. Anti-submarine cover for the Brindisi–Cape Lefkada leg of her voyage would be provided by CANT Z.501 flying boats of the Taranto Command; aircraft from Patras, Greece would then take over until last light. By early on the 6th the British knew that Sestriere could now only make 12½ knots and they had the revised timings and coordinates of her route. They also had a breakdown of the supplies she carried for each of the three services; the names of the flying boat captains who had covered the initial stages of the voyage; and that six Bf 110 had moved from Africa to Kastelli to escort her. The Germans signalled that the convoy had been sighted by RAF reconnaissance at 06.15 that day.
No. 160 Sqn. had several encounters with Bf 110s and Ju 88s escorting convoys but the Sestriere mission seems to have been their only report of an He 111. Eight Liberators were dispatched on 6 October, briefed for a dusk attack on a 6,000 GRT merchant vessel and five escorts expected to be about 80 km SW Crete at 1700 hours. They were to search a 25-mile radius and in fact found the convoy about 18 miles from the expected location. Four of the force either turned back or could not find the target. Of the remainder, F/O E.A. Duplex’s crew (flying as “Blue 1” in AL555) spotted a large merchantman and four destroyers at 18.37 hours. Nine minutes later they saw “one Heinkel as escort which fired red-red [signal flares]” while active opposition came from three Bf 110 and a Ju 88. Unusually we have both sides’ accounts of what followed. Because Duplex’s aircraft had bombsight trouble, the four Liberators made a dummy run in formation before turning to starboard for a second pass at 11–12,000 ft. Flying Officer W.J. Jenner (AL638) heard the command to turn but not the direction and became separated, only to be attacked and hit by two Bf 110 which wounded Wireless Operator Sgt. J.S. Elliott in the leg while he was holding the bomb doors open. The fighters also smashed the mid-upper turret of Sgt. W. Wilson’s AL548. Only near misses were claimed on the ships but:
One Me 110 seen to hit sea. Another Me 110 seen last at 1,000 feet with flames and losing height. One Ju 88 last seen in steep dive at 1,000 feet with one engine stopped and smoke from other engine.
The Luftwaffe attributed the attack to “four American Liberators” and believed that “their immediate engagement” by the escorting aircraft had compelled them to jettison their bombs before reaching their target (the bombers on the other hand claimed near misses). Two of the Liberators were seen to be trailing smoke as they departed the scene.
At the time of the attack, the close escort consisted of three Bf 110 from III./ZG 26 and two Ju 88 of I./KG 54. Four more Ju 88 were providing distant cover but there is no mention of the reported Heinkel which was in fact probably the second Ju 88 (a Kdo. Koch He 111 providing Wildschwein support to the convoy only left Kalamaki at 17.30 so could not have reached the scene of the action until about two hours after the RAF had gone). Away from the convoy, Flight Sergeant F.P. Russell’s AL579 had lost contact with the others, was “attacked by fighter” while heading back to Egypt and its bombs were jettisoned into the sea. No more details were given so apparently the Liberator was undamaged.
During the day, Fliegerkorps X had deployed the following on escort for the Sestriere convoy:
Another 7 Bf 110 either broke off with technical troubles or failed to find the ships in the bad weather (both sides reported electrical storms). No ships were hit; overnight the Italians were to fly escort and the following morning there was to be continuous cover by two bombers from Fliegerkorps X as well as three Bf 110 or 109 and Italian aircraft.
Casualties from the Fliegerkorps X escorts were:
Only two of the above aircraft were included in loss reports to the Quartermaster General:
The escort vessels’ next deployments had been decided early on the 6th (and read by the British that afternoon) while the convoy was still at sea. Air cover from first light on the 7th would consist of two Fl.Kps. X bombers together with unspecified Italian aircraft. In the early hours of the 7th it was known that the convoy was three hours behind schedule and what its route to the Libyan coast and thence to Benghazi was to be. Sestriere entered harbour at 11.00 that day, bringing 390 tonnes of army cargo; 4 t for the navy; and 680 t for the Luftwaffe, including 336 t of B4 fuel. Unloading was expected to be complete by the 11th.
Horizontal bombing of moving ships from medium or high altitude does not seem to have particularly successful in any theatre (see for example to use of B-17s in the Battle of Midway) and an RAF analysis of the October–December 1942 campaign against the Axis convoys found that for every ton of bombs dropped, 43 tons of shipping were sunk. By contrast, every ton of torpedoes sank 703 tons and damaged 469 tons. Statistically, Liberators outperformed Wellingtons at sinking ships but flew only 31 strike sorties against the former type’s 869 (Swordfish and Albacores proved by far the most effective types).