The apparent ebb in the U-boat war is due to a single technical invention of our enemies. Not only are we in process of countering this but we are convinced that in a short time we shall have succeeded in doing so.
Führer Order of the Day to the Wehrmacht (2 January 1944)
The enemy makes wide use of centimetre-wave sets for location from aircraft and surface craft … only audible on ’Naxos’ when beam sweeps across the boat … Efforts are being directed to equipping boats with a better set …
BdU Serial Order No. 41 (5 January 1944): Use of ’Naxos’ Set
Bordeaux-Mérignac was heavily bombed on 5 January and this is thought to have been the date when an He 111 of the Kommando was seriously damaged. A photograph from the collection of the late Manfred Griehl shows the machine with an MG FF cannon in the nose position and beam MG 17s; the discernible part of the fuselage code appears to read +S with a final character rendered illegible by damage.
On 20 January, in the first of the unit’s operations for the year (as far as the Allies knew) an He 111 of the “Special Detachment” was due to take off at 2230 and cross the coast due west of Bordeaux, its return expected between 0630 and 0730 next morning. At 0557 F8+DI gave its estimated time of arrival at base as 60 minutes hence. It was over Mérignac at 0647 but was unable to land owing to bad weather and was diverted to Istres. Six nights later, the intention was for an He 111 to fly out at 2315 and return by 0800 the next morning. Aircraft “I”, using a II./KG 40 call sign, was in contact with Bordeaux shortly after 0200, when it was plotted about 360 km NW of Mérignac. Just over four hours later, F8+DI was heard in touch with ground stations at Dreux and Bordeaux.
The operation by the Kommando on the night of the 28/29th sparked a flurry of German activity when F8+DI called in a sighting of 200–300 landing boats 200 km west of Royan. The aircraft’s control ordered it to shadow at 0207, but it failed to reply to a call 20 minutes later. It probably did little to alleviate the tension that the crew was similarly unresponsive when asked at 0352 if it was indeed shadowing, and to a request at 0510 to report the vessels’ course. However the Heinkel was homing on Mérignac from the NNW at 0636. Meanwhile three vessels of the 8th Destroyer Flotilla had set out from Le Verdon-sur-Mer at 0415, while coastal patrol forces were placed at immediate readiness and it was mid-morning on the 29th before the whole thing was found to have been a false alarm.
Even so, a call came through from Gen. Jodl at OKW requesting that the destroyers search the boats “for arms, radar equipment or evidence of British connections” but it seems the Navy was able to reassure him that this was a regular fishing ground and that all searches to date had yielded nothing. British Intelligence produced its own assessment of the fiasco:
… Rastedter engendered a panic on 29/1. The … He 111 evidently received a blip and interpreted it as 200–300 landing craft approaching the French coast; a U-boat appeared to confirm this by reporting an Allied convoy with air escort n the same area. 3 a/c of ex-16./KG 40 [= 9./ZG 1] were sent off at once to investigate. U-boats were to proceed at high speed on the surface to the area and three destroyers put to sea. [9./ZG 1] reported that the formation was actually 18 Spanish trawlers and the panic subsided. The maximum possible number of patrols were flown by I./ZG 1 and 1.(F)/128 during the day, presumably to protect the destroyers, two of which later collided with each other.
Another aspect of the radio countermeasures war being played out in the Bay came to British attention during January. From the 18th there were operations from Avord by III./KG 40, “as yet unexplained.” A week later these were discovered to be by the 9. Staffel in cooperation with a patrol boat and by the first days of February (see below), the vessel in question was known to be setting out reflector buoys, as prefigured in this signal of 11 January:
In order to interfere with the enemy location activity, type Thetis 20 decoy buoys (Täuschungs-Bojen) will be laid out in Biscay as far as approximately 12º West with effect from 11 January.
Description: a thin, upright wooden pole 5 metres long on a float, weighted at the bottom by a 5-metre long steel tube. On the wooden pole, thin metal dipoles visible only at very close range.
Method of operation: the buoy produces the same location reflex [radar response] as a U-boat.
Intended to appear identical on radar to a U-boat.
At midday on 1 February an Fw 200 of III./KG 30 (thought to be Fw 200 C-4, W.Nr. 0012, NT+BL) was due to fly out over the Gironde Estuary for exercises over a 50–100 km radius offshore in conjunction with a “naval auxiliary vessel”. Bletchley Park noted that this ship was “known to have been very recently concerned in experiments with a Radar decoy buoy, designed to give a similar Radar ‘echo’ to that obtained on a U-boat [and] intended for use in the Biscay area”.
A nine-hour operation was intended on 5 February but no corroborating W/T traffic was heard. The next day, an He 111 was due to take off at 2345 and come home between 0745 and 0845. Traffic early on the 15th would permit the identification of another of the Kommando’s Heinkels: DT+YI (He 111 H-16, W.Nr. 8308) homed on Bordeaux from 0614, giving its ETA as 0700.
More intelligence was derived the following day: the Kommando had become Horch- und Störstaffel 2 ("Listening and Jamming Staffel 2" to the Allies) and acquired its own unit code, 9U+_B. At 2230 it was reported that He 111, 9U+CB had taken off 15 minutes previously and would be returning between 0615 and 0715. (The same aircraft was identified in W/T traffic between 0228 and 0320 on the 17th). The intention for 16 February (communicated to destroyer ZH 1) was that He 111
A major Luftwaffe effort had taken place in the Bay of Biscay on the 25th, to bring home U-714 which was carrying the survivors of the scuttled U-545. However the submarine had docked in Saint Nazaire by 2230, the time the night’s He 111 was due to take off (with landing foreseen for 0600–0700 the following morning). On 29 February, destroyers ZH 1 and Z 23 were told that 9U+CB was to take off at 2215 and return to Mérignac between 0615 and 0715 next day but—as was far from uncommon—there was no intercepted W/T to show that this sortie took place.
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