REPORT ON INTERROGATION OF SURVIVORS FROM TWO 500-TON U-BOATS,

U 473 SUNK BY SHIPS OF ESCORT GROUP 2 on 6th MAY, 1944, and

U 765 SUNK BY A SWORDFISH FROM H.M.S. "VINDEX" and

ESCORT GROUP 5 on 6th MAY, 1944.

______________________________

I.  INTRODUCTORY REMARKS

(i)     U-473

        U 473, a 500-ton Type VII C U-boat, under the command of Kapitänleutnant Heinz STERNBERG was sunk in position 49° 29' N., 21° 32' W. by H.M. Ships "STARLING", "BENTLEY", "WREN", "GORE" and "WILD GOOSE" on 6th May, 1944.

(iii)   Equivalent Ranks

Kapitan zur See		Captain
Fregattenkapitän		Commander
Korvettenkapitän		Lieutenant Commander
Kapitänleutnant		Lieutenant
Oberleutnant zur See		Sub-Lieutenant
Leutnant zur See		Junior Sub-Lieutenant
Oberfähnrich zur See		Senior Midshipman
Fähnrich zur See		Junior Midshipman

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II.  DETAILS OF U 473 AND U 765

U 473			U 765
(i)  Type:	VII C		VII C.
(ii)  Tonnage:	500 tons		500 tons
(iii)  Building Yard:	Deutsche Werke, Kiel		Deutsche Werke, Wilhelmshaven
(iv)  Commissioned:	Beginning June, 1943		19th July, 1943
(v)  Armament:
(a)  Guns:	One 37 mm. fully automatic on lower bandstand		One quadruple 20 mm. on lower bandstand.
	Two twin 20 mm. on upper bandstand		Two twin 20 mm. on upper bandstand
(b)  Ammunition:	On her first patrol U 473 carried ordinary A.P. for the 20 mm.  This was changed in Lorient for "Minenspreng" ammunition.  The 37 mm. ammunition was "Minenmunition."
(c)  Torpedoes:	Ten carried.  Six of these were Eto Fat, some of which were T 3A, and four were T 5.		Ten carried.  Eight of these were T 3 and two were T 5.  The T 5 were loaded in Tubes III and V
	Two T 5 torpedoes were loaded in Tubes II and V.  One was stowed forward and one aft.
	On her first patrol (March 1944) U 473 carried 10 torpedoes stowed as follows:
	Tube I T 3A Tube II T 5 Tube III T 3 Tube IV T 3 Tube V T 3 Port upper T 3 Port lower Fat I Starboard lower Fat I Starboard upper Fat 1 After bilge T 3A

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U 473			U 765
(c)  Torpedo Tubes:	U 473 had bronze torpedo tubes		U 765 had steel torpedo tubes with four bronze rails inside them.  The tubes were continually rusty.
(vi)  Radar:	None carried		None carried
(vii)  G.S.R.:	U 473 carried experimental G.S.R. equipment similar in most respects to that installed in U 406 (See C.B. 04051(99)).  For description of this equipment see Section V (i).  U 473 carried Wanz II, Borkum, and Naxos G.S.R.  She had one drum-shaped aerial and one standard Naxos aerial which was installed before the last patrol.  An order was received not to use Radione in connection with the Naxos set but to attach the headphones direct to the amplifier stage.		U 765 carried Naxos, Wanz II and Borkum.  She carried two aerials for the Naxos.  One was a Fleige type aerial (See Section V (i) a     ).  The other was a normal Southern Cross aerial.  The Wanz was operated with a drum shaped aerial.
(viii) Infra-Red Apparatus:	U 473 carried "seehund" and "Flamingo" apparatus.  For description of this apparatus see C.B. 04051(99), page 9.
(ix)  Hydrophones:	One prisoner stated that G.H.G. and K.D.B. were fitted.  A special log of all noises heard on the K.D.B. in the Bay of Biscay had to be kept.
(x)  Flotilla:	Attached to the 9th Flotilla, Brest, but never reached the port.		Was to join 1st Flotilla at Brest on completion of her sole patrol.

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III.  LAST PATROL AND SINKING OF U 473

(i)  Departure from Lorient

        U 473 left Lorient on 27th April, 1944, with orders to proceed direct to her operational area.  She was escorted out of harbor by three minesweepers.

(ii)  First attack by Aircraft

        Shortly after leaving Lorient U 473 was attacked at night by an aircraft which approached the boat from astern and switched on its searchlight partially illuminating the U-boat.  The guns' crews immediately opened fire and the aircraft turned and made off.  In turning it presented a very good target to the U-boat's fire, and prisoners thought that if their aim had been more accurate they could easily have brought this aircraft down.  (N.I.D. Note:  At 0327 on 28th April, 1944, an attack on a U-boat was carried out by a Halifax M/58 in position 46° 58' N. 10° 30' W.  The aircraft on anti U-boat patrol had a radar contact at eight miles and on homing dropped flares and sighted a U-boat fully surfaced, course 225 speed 15 knots.  Aircraft attacked with seven 250 lb. Torpex D/Cs from 100 ft., spacing 80 ft. which are believed to have straddled the U-boat.  During this attack the aircraft was hit by flak, but the captain regained control.)

(iii)  Second attack by Aircraft

        Shortly afterwards U 473 was again attacked by a four-engined bomber which dropped four bombs in the immediate neighborhood.  No damage was done.  (N.I.D. Note:  At 0215 on 29th April an attack was made by a Wellington W/304 in position 45° 30' N., 11° 00' W.  The aircraft on anti-U-boat patrol obtained radar contact at five miles, homed and sighted in the moonlight a fully surfaced U-boat at half a mile.  Aircraft attacked with six 250 lb. Torpex D/Cs from 50 ft.  Saw last explosion about 20 yards ahead of U-boat, the remaining explosions being obscured.  Aircraft shadowed U-boat for one hour, U-boat remaining on surface during this time.)

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        Throughout these attacks prisoners counted 334 D/C explosions.  The U-boat was submerged for about 20 hours but as none of the D/Cs exploded beneath the boat very little damage was done.

        After an initial dive to 180 m.  (590 ft.), U 473 was steadied on 200 m.  (656 ft.) and remained at that depth for most of the attacks.  She never went deeper.  The CO2 content gradually rose 3.5% and both batteries and high pressure air were very low.  (N.I.D. Note:  After having harassed and attacked the U-boat all day the S.O. of the Support Group decided to wait until she came up for air.  After dark "STARLING", "WILD GOOSE" and "WREN" followed about one mile astern of their victim on a north westerly course while "BENTLEY and "GORE" took station six miles to the North Westward to cut off the U-boat if she tried to escape at high speed.)

        U 473 finally surfaced at 0014, 6th May, when owing to the condition of the air in the boat, it was impossible to remain submerged any longer.  She was immediately engaged by the attacking destroyers.  (N.I.D. Note:  The U-boat surfaced at 0014 on 6th May and was immediately illuminated and engaged by "STARLING", "WILD GOOSE" and "WREN".  All ships scored numerous hits on the high speed zig-zagging U-boat.)  As soon as she surfaced a T 5 was fired from the stern tube which missed the stern of a destroyer by 3 metres.  The order was given to prepare tubes I, III, and IV, but before STERNBERG could give the order to fire, he was killed on the bridge and these tubes were never fired.  (N.I.D. Note:  At least one torpedo was fired which passed down "WREN'S" port side.)

        One prisoner stated that a shell penetrated the conning tower and damaged the electric steering gear.  (N.I.D. Note:  Early on in "STARLING" it was difficult to see the target in the surf and spray, but later a red glow in the conning tower provided a perfect aiming mark.  "STARLING" herself fired 133 rounds of 4-inch H.E. from "A" mounting.  "WILD GOOSE" refers to five H.E. shells which were fired at this particular U-boat.  Shell No. 1 was observed to hit on the water-line forward of the conning tower, it penetrated and burst; no damage was observed.  Shell No. 3 hit on after gun platform, threw gun overboard and opened up the hull.  Shell No. 4 burst well forward, no damage observed.  Shell No. 5 hit on water line about 12 ft. abaft the conning tower, penetrated and burst internally.)  No sinking report was made to Control as all W/T gear had failed during the depth charge attack.  (N.I.D. Note:  The ship's company soon took to the water and the U-boat was left circling at high speed.  She finally sank in position 49° 29' N., 21° 22' W.  at 0033.  Two small underwater explosions were heard at 0035, probably scuttling charges and at 0042 a very heavy explosion marked the end of U 473.  Thirty prisoners were picked up.)

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IV  LAST PATROL AND SINKING OF U 765

(i)    Commencement of Patrol

        U 765 left Kiel on 18th March, 1944.  She proceeded without escort to Kristiansand S., where she remained about seven hours topping up with fuel.  She was then escorted to Bergen and spent about ten days there, undergoing repairs to a joint in the pressure hull.  On 3rd April she left Bergen, accompanied by an A/S vessel and two VII C type U-boats.

(ii)    U 765 as Weather Reporter

        After parting company with the other U-boats and the escort, U 765 proceeded through the Rosengarten to take over weather reporting duties from a U-boat commanded by REFF.  She remained in an area south of Iceland (C) about fourteen days, subsequently moving southward to operate off the coast of Ireland (R) and changing her area of operation every eight days.

        (N.I.D. Note:  During the forenoon of 30th April orders were received for H.M.S. "VINDEX" and the 5th Escort Group, consisting of H.M. Ships "BICKERTON", "AYLMER", "KEMPTHORNE", "GOODSON", "KEATS" and "BLIGH" to proceed to the vicinity of 52° N., 30° W., to hunt a U-boat apparently patrolling there on weather reporting duties.

        At 0840 2nd May, when position 53° 42' N., 28° 00' W. had been reached, a U-boat making a WW message was heard bearing 035° fairly close, but not within 30 miles.  The force was turned in that direction to sweep, but at 1104, a message from Admiralty placed the U-boat to southward which seemed to indicate that bearing was reciprocal and as this was confirmed by a signal intercepted from H.M.S. "HOSTE", course was reversed and sweep carried out to the southwestward.

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        A depth charge attack developed.  At this time diving tank Ii (Internal Tank 1) was leaking and was having to be blown practically continuously.  After the first series of depth charges it also became necessary to blow the outer tank I continuously due to the boat being stern heavy.  Diving tank III developed a leak into the control room and U 765 was driven down to a depth of about 260 metres (853 ft.) by the depth charges.  Another series of depth charges then blew the boat up towards the surface again.  By this time there was a water entry aft near the Diesels, the drinking water distiller was lying on the floorplates, smashed, and the bow hydroplanes were destroyed.  Just before surfacing there was a dispute between the Commanding Officer and the Engineer Officer.  WENDT ordered the Engineer Officer to take the boat down to 100 metres (328 ft.).  U 765, however, was now about 60 metres (196 ft.) and was steadily rising out of control.  WENDT then entered the conning tower and as soon as the boat surfaced he abandoned ship without giving any further orders.  The boat sank after being on the surface for about half a minute.

        (N.I.D. Note:  Shortly after 0410, "KEATS", having obtained A/S contact, carried out a series of depth-charge attacks.  These attacks, however, were made on a non-submarine target.

 

        At 0518 in position 52° 21' N., 28° 30' W., while still about 2-1/2 miles from "KEATS", "BICKERTON" obtained a contact classified as submarine.  "BLIGH" began a creeping attack at 0540 and delivered it at 0603.

        The last charge had scarcely exploded when the U-boat conning tower was seen to break surface in the centre of the pattern.  Fire was opened by "BICKERTON", "BLIGH" and "AYLMER", a number of hits being obtained.

        While the gun action was proceeding a Swordfish from "VINDEX" dropped two depth charges which straddled the boat and hastened her end.  Eleven survivors were picked up.)

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V.  GENERAL REMARKS ON U-BOATS

(i)     Experimental G.S.R. Equipment carried by U 473

        Permission had been sought from Grossadmiral DOENITZ to use U 473 as a G.S.R. experimental boat.  This was, however, refused and she was ordered to sail operationally, but to continue with her trials.

 

        The experimental gear carried resembled in many ways that carried in U 406 (See C.B. 04051(99)).  The wave bands covered were 5 cm. to 320 cm.  A prisoner thought that this probably excluded the "Fliege" combination.

        U 473 carried seven W/T ratings, which included one P.O. Telegraphist, one Leading Telegraphist, three W/T operators for routine W/T work and two additional ratings who had taken a special six months course in G.S.R.

          (a)  Aerials

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	2.	"FANÖ"	This set is identical in appearance with "SAMOS" but covers the wave-band immediately below.  It should have been used with "PUDEL" but, since it radiated badly, was not so used.
	3.	"WANZ G. II"	Radiated slightly but not seriously.  Was kept switched on circuit with "BULLDODGE" and "PUDEL".  This set was never used in U 473.
	4.	"BULLDODGE"	This combination consists of the large drum-shaped aerial + Borkum + Hela + oscillograph + headphones.  "SAMOS" can also be used with it.  One prisoner said that this set covered from 80-320 cm.  (Hela amplifiers are described in (d) below.)
	5.	"PUDEL"	This combination consists of the smaller drum-shaped aerial + Borkum + Hela + oscillograph + headphones.  "FANO" could also be used with it but never was in U 473.
			No contacts were received with "BULLDODGE" and "PUDEL" during the patrol.
			One man kept a joint watch on the "BULLDODGE" and "PUDEL" combinations.
	6.	"SPITZ"	This combination covers 12-36 cm. and consists of Cuba aerial, Hela II, Borkum and polarisatic switch.  The range is 20 - 30 Km.  The combination was given by another prisoner as Cuba aerial + Borkum + Hela + headphones and  oscillograph.  The frequency meter could also be used, but was not during U 473's patrol.  Hela I was also said to have been used with this combination.
	7.	"DACKEL"	Consists of Cuba aerial + Borkum + Hela + headphones + oscillograph.
			The combination was given by another prisoner as Cuba + Hela I + Borkum covering 5-12 cm.  Range 20-30 Km.  Bearing of contact cannot be obtained.
			One man kept a joint watch on the "SPITZ" and "DAKEL" combinations.
			Borkum, used in normal boats as a G.S.R. set, was used in U 473 only as a rectifier.  Two were carried and were only used with "DACKEL" and "SPITZ".  Another prisoner stated that four Borkum rectifiers were carried and were used with all combinations except "FLEIGE".
	8.	"FLEIGE"	This combination consists of Fliege aerial + Hela + amplifier + headphones.  Contacts were always obtained whenever "SPITZ" and "DACKEL" were receiving them.
			Requires a 220 Volt A.C. supply.  Contacts strength 2, were obtained from a Rotterdam set at a distance of 70 Km.
			The FLIEGE" was said to have picked up transmissions off Northern Ireland (R) and after research it was thought that the Allies were probably working on 2 to 4 cm. as it was believed that certain contacts were not fundamentals but higher harmonics.  A new cable

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			for the "FLIEGE" aerial was used in U 473 and U 765.  The cable, which was armored, was 1-1/2 cms. in diameter and was blue in color.  It increased the range from 35 Km. to 45 Km.  The cable was brought from Berlin by Professor SCHWARZ just before U 765 left Kiel on 18th March.  (N.I.D. Note:  According to a captured document "FLIEGE" is identical with Cuba 1.a  See C.B. 03122, S.N.,I.P. (M.P.) 81/44).
	9.	"KRAHWINKEL" Set	Tried out experimentally but not carried.  Designed for obtaining a continuous note from a passing contact.

          (c)  Testing Sets

	1.	Famulus	Two Famulus sets were carried.  The test set consisted of a small box with a buzzer inside.  It was never used.
	2.	Bug	Bug was a small box containing a buzzer similar to Famulus.  Was used exclusively for testing the sets, by holding it near the aerial.  Two of these sets were carried.

          (d)  Hela Amplifiers

                Amplifiers known as Hela I and Hela II were carried in addition to four others.  Hela I and Hela II were 6 or 8 valve low-frequency amplifiers with E.F. 13 steel valves.

          (e)  Oscillographs

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and is connected via a circuit to a cathode ray oscillograph with a circular trace.  The Flamingo did not set up any interference on other sets.  (See also C.B. 04051(99), page 9).

(iii)    Emergency Transmitters

        A prisoner mentioned a new automatic emergency transmitter with a range of 200 Km. for fitting to dinghies.  It sends out S.O.S. followed by 5 dots.  There is also a key but it may only be used for making S.O.S. signals.  Two aphrodite balloons (R.D.E.) may be adapted for an aerial or if there is sufficient wind a box kite, which takes about one hour to assemble, can be used.  The kite is carried in a large metal container.

        Another prisoner spoke of a similar transmitter which is being developed by Oberleutnant KUGELMEIER and the C.P.O. Telegraphist of the 2nd Flotilla in Lorient.  It is to work automatically on 600 m.

(iv)   Very Long-wave Transmitters

        In addition to the very long-wave transmitters at Nauen and Kootwijk, there is one near Warsaw.  The Kootwijk transmitter has a strength of rather more that 350 kilowatts and Nauen is more powerful; it is not however equal to Goliath.

(v)    U-boat Wavelengths

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(xi)   Small U-boat

        A prisoner from U 473 knew of three small U-boats, two at Hel and one at Swinemünde, with a complement consisting of the captain and eight C.P.O.s and P.O.s.  They never left the harbor except at night and during the day were heavily camouflaged and quite inaccessible.  The boat in Swinemünde was about 25 m. long (82 feet) with a glass cupola.  Part of the rudder projected above water about 8 feet from the visible stern.

        (N.I.D. Note:  Probably refers to prototypes of 110' type of small U-boat building at Hamburg, of which none is believed (July/August 1944) yet in operation.)

(xii)  Japanese Submarine

        When U 473 was in Lorient from 20th-27th April, 1944, a large 2,200 ton Japanese submarine was in one of the shelters for part of the time.  It sailed a few days before U 473.  The boat was so long that it protruded from the shelter and there was only a 6ft. 6 ins. clearance between the boat and the wall of the pen.  Two guns were mounted, one forward and one aft, and she had a folding aerial.  Other who had seen the boat said there was an electric cable wound round the hull.  She was unloading rubber and gold.  She left with a cargo of high tension cable and some medical stores.  She was also said to be taking eight Japanese students back to Japan.  When U 473 was at sea on her last patrol a signal was intercepted from this submarine reporting her safe passage through the Bay of Biscay.

(xiii)  Camouflage

        U 473 was camouflaged with special dark grey paint which was intended to absorb infra-red.

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VI  BASES AND TRAINING ESTABLISHMENTS

(i)     France

        (a)    Brest

                There is an enormous G.S.R. station near Brest, which is said to be the largest shore station of its kind.  Its main purpose is to watch for Allied aircraft crossing the coast.

(ii)    Germany

        (a)   Hamburg

                In the Howaldtswerke there is a U-boat shelter which can accommodate six boats.  It is divided into two pens, the roof of which is 16 ft. thick; it is entered through steel doors.  U-boats undergoing final adjustments lie here.  Inside the shelter is a complicated electric generating station.  Two fire engines are kept outside and at night the shelter is used as an A.R.P. shelter by the public.  Railway trucks can be brought right into it.

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(i)    Commissioning

        U 473 was built at the Deutsche Werke, Kiel.  She was commissioned at the beginning of June 1943.

(ii)    Working-up

        On leaving Kiel she proceeded to Swinemünde where the ship's company received Flak instruction.  From there she went to Hel for about six weeks "Agru-front" exercises and then to Libau for about three weeks torpedo firing.  After calling at Pillau for degaussing and to go over the measured mile, she carried out three days silent running trials at Rönne and returned in October to Kiel, where the 37 mm. was mounted.  At Kiel the G.S.R. and infra-red equipment was fitted.

        From Kiel U 473 proceeded to Neustadt and Pelzerhaken, spending one night at each.  At Pelserhaken Dr. KRAHWINKEL came on board.

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PREPARATIONS FOR SEA OF U 473, 12th to 15th MARCH, 1944, AT KIEL.

                                                                                 (From a Captured Document)

		March	Time
Instruction of W/T personnel and W/T officer		14th	0800		By Flotilla Officer
G.S.R. instruction.  Compulsory for all officers, W/T personnel and auxiliary (G.S.R.) operators		15th	1400		In W/T office St. Louis
_________________________________________________________________________
Gunnery instruction for Second Watch Keeping officer, Boatmans Mate and Ordnance rating A		12th			Deck A Cabin 64
_________________________________________________________________________
C.O.'s Instruction		14th	0815		St. Louis, Operations Office.
_________________________________________________________________________
Preparations and Trials before going on patrol
D/F calibration		15th	0900		Lying near Buoy A 13.
_________________________________________________________________________
Embarking Torpedoes		12th	0900		Berth 13.
_________________________________________________________________________
Embarking Ammunition		13th	1600		Inside Shelter.
_________________________________________________________________________
Embarking tinned provisions; including bread and potatoes.		19th	0600		Berth 33
_________________________________________________________________________
Embarking fresh provisions		15th	1200		Berth 33
_________________________________________________________________________
Embarkation of armament and dinghies		14th	1000		Berth 33
_________________________________________________________________________
Wiping.  Pilot		12th	1600		Old lock.  5 short blasts.
_________________________________________________________________________
Compass Adjustment.  Unscrewing caps of mirror system.		14th	1400		Lying in B-system near Monkeberg steamer landing stage 5 short blasts on hooter
_________________________________________________________________________
Hydrophone Trials		14th	1600		Near buoy 13.  Prepare for diving.
_________________________________________________________________________

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		March	Time
Final Trimming Test.  Engineer Officer report U-boat base Office for orders two days before trials.		15th	0800		At this time boat to be 300 m. off Tirpitz Mole.
_________________________________________________________________________
(i  Celebration		15th	1700		Smoking Room St. Louis
_________________________________________________________________________
(ii  Leave on patrol.		16th			As per special orders.
_________________________________________________________________________
C.Bs. and Secret Documents		13th	1500		Deck E, cabin 113
_________________________________________________________________________

        Boat to be in the shelter of Howaldt Dockyard from 12th to 15th March 1944.  In the shelter diesels must not be warmed up and no charging is to be done by Diesel.  Caution when maneuvering.  Beware of hydrophones and propellers.

        Refill and top up all diving and inner tanks with oil.  Ventilate.  Type VII C boats to keep regulating tanks full for final trimming test.

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(i)  Survivors:

Name	Rank	English Equivalent	Born
GRAMMS, Wilhelm	Oberleutnant (Ing.)	Sub-Lieutenant (E)	19.5.06.

Officers		1
Chief & Petty Officers		5
Men		24
	Total	30

(ii)  Casualties:

Name	Rank	English Equivalent
STERNBERG, Heinz	Kapitänleutnant	Lieutenant
SCHULZE, Heinz	Leutnant zur See	Junior Sub-Lieutenant
STROHM,	- do -	- do -

Officers		3
Chief & Petty Officers		5
Men		12
	Total	20

Officers		4
Chief & Petty Officers		11
Men		35
	Total	50

Officers		2
Chief & Petty Officers		9
Men		--
	Total	11

Officers		-
Chief & Petty Officers		3
Men		33
	Total	37

Officers		3
Chief & Petty Officers		5
Men		40
	Total	48

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