Copy No. ___ of 50.

NAVY DEPARTMENT

OFFICE OF THE CHIEF OF NAVAL OPERATIONS

WASHINGTON

Final Report - G/Serial 31

REPORT ON THE

INTERROGATION OF SURVIVORS FROM U-761

SUNK 24 FEBUARY 1944

S E C R E T

TABLE OF CONTENTS

				Page
CHAPTER	I.		INTRODUCTION	1
	II.		DETAILS OF U-761	2
	III.		GENERAL REMARKS ON U-BOATS	9
	IV.		CREW OF U-761	13
	V.		EARLY HISTORY OF U-761	16
	VI.		FIRST PATROL OF U-761	18
	VII.		SECOND AND LAST PATROL OF U-761	23
	VIII.		SINKING OF OF U-761	27
	IX.		OTHER U-BOATS	31
	X.		BASES	41
ANNEX			CREW LIST OF U-761 AND U.S. EQUIVALENT OF GERMAN NAVAL RANKS

CHAPTER I.  INTRODUCTION

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CHAPTER II.  DETAILS OF U-761

TONNAGE.

        500 tons.

TYPE.

        VII C.

BUILDING YARD.

        Kreigsmarinewerft, Wilhelmshaven.

COMMISSIONED.

        2 December 1942.

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BRIDGE AND PLATFORMS.

        Bridge armor fitted.  Platform II added during final overhaul at Deutsche Werke, Kiel, summer 1943.

GUNS.

        1)  Automatic 37-mm. on Platform II; one reserve barrel carried.  Barrels could be exchanged in 15 minutes.

        2)  Two twin 20-mm. cannons on Platform I; type 38, no shields.

        3)  Four demountable machine guns, type 15;

        4)  Original equipment:  88-mm gun forward of bridge removed during final overhaul at Deutsche Werke, Kiel, summer 1943; one 20-mm. canned added on Platform I during final overhaul; quadruple 20-mm. mount fitted on Platform II during final overhaul.  The latter two replaced by (1) and (2) after first patrol, at Brest January 1944.

AMMUNITION.

        1)  4000 rounds of 30-mm ammunition carried.  Distributed as follows:  In magazine 2760 rounds; in control room 800 rounds; in conning tower 160 rounds; 280 rounds in pressure-proof ammunition lockers on Platform I.

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PRESSURE-PROOF AMMUNITION LOCKERS.

        Two on keel line on Platform I for 20-mm. ammunition; 3 on Platform II, of which 2 were located forward, port and starboard of the 37-mm. gun which they served, and one located directly aft of the gun.

TORPEDO TUBES.

        4 forward, one aft.

TORPEDOES CARRIED.

        Probably 10 carried on last patrol, 12 carried on first patrol.        

UPPER DECK CONTAINERS.

        Not fitted.

S.B.T. (Submarine Bubble Target)

Telegraph Speeds	R.P.M.
K.F. (Dead Slow)	180
L.F. (Slow)	286
H.F. (Half Speed)	348
2xH.F. (3/5 Speed)	392

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Telegraph Speeds	R.P.M.
G.F. (3/4 Speed)	443
A.K. (Full Speed)	472
3xA.K. (Emergency Speed)	487

SUPERCHARGERS.

        Two Rootes type superchargers.

FUEL OIL CAPACITY.

        115.95 tons carried on last patrol.

FUEL OIL CONSUMPTION (compiled from a machinist's diary).

Telegraph Speeds             Hourly Consumption in liters
L.F. (Diesel-Electric)	137 (one Diesel)
H.F. (Half Speed)	390 (Both Diesels)
2xH.F. (3/5 Speed)	430 (Both Diesels)
G.F.  (3/4 Speed)	592 (Both Diesels)
G.F. (3/4 Speed) Charging battery	600 (Both Diesels)

LUBRICATING OIL CAPACITY.

        4660 liters carried on last patrol.

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MOTOR SPEEDS

        Identical with electric motor speeds of U-664 (G/Serial 27).

ELECTRIC MOTOR AMPERAGE (from a captured document)

K.F. (Dead Slow)	200 Amperes
L.F. (Slow)	225 Amperes
H.F. (Half Speed)	850 Amperes
G.F. (Full Speed)	2200 Amperes
A.K. (Emergency Speed)	3000 Amperes

COMPRESSORS.

        One electric, one Junkers air compressor.

OXYGEN SUPPLY.

        3000 liters.

GERMAN ASDIC.

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RADAR DECOY SPAR BUOYS (R.D.S.)

        Not carried.

G.S.R.  (German Search Receiver)

        1)  Wanz G-2.

        2)  Naxos; two sets carried, interchanged every 2/3 days.

        3)  Borkum.

G.S.R. AERIALS.

        1)  Basket-type dipole aerial.

        2)  Dipole Naxos aerial.  Two spare aerials carried;  at least one of these was fitted with a semi-circle plexiglass rod to protect the dipole.

        3)  Cross-type aerial carried as spare.

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        3)  U.K. (VH/F) gear removed at final overhaul summer 1943.

EXTENSIBLE ROD AERIAL.

        Not fitted.

HYDROPHONES.

        "Elak" G.H.G. fitted.

ECHOSOUNDER.

        "Elak" echosounder fitted.

SCUTTLING CHARGES.

        Located in forward torpedo compartment, control room, stern compartment.

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CHAPTER III.  GENERAL REMARKS ON U-BOATS

HOHENTWIEL RADAR

        This radar set is reported to contain a crystal self-tuner, and it is claimed that it can be tuned on the target.  It is keyed on plate current instead of grid current.  The mattress aerial is believed to be somewhat smaller than the aerial used with Gema-Radar sets.

        It is believed that Hohentwiel Radar will first be fitted on U-boats which have no radar installation, secondly on U-boats with damaged sets, and last on U-boats equipped with a Gema installation.

"BERLIN" RADAR

        The radar set called "Berlin" was stated to be copied from radar sets found in American bombers which crashed over Germany.  The aerial used in connection with the set was described as a curved reflector aerial.

BORKUM G.S.R.

        On some occasions the Borkum G.S.R. set was switched to the Naxos aerial and short wave R/T was then heard on it.

FREQUENCIES

        On the last patrol of U-761 (12 - 24 February 1944) one of the frequencies of the Kustenschaltung (Coast Frequency Ranges) was 4260 kcs; one of the frequencies of the Diana-

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Schaltung (Diana Frequency Range) was 21.3 kcs.

RADIO INTELLIGENCE

        A radioman, at present hospitalized, was stated to speak English and to have listened to Allied convoy traffic.  It is unknown whether the primary purpose was to intercept voice traffic or to obtain bearings on approaching convoys.  A book on convoy voice traffic was kept on U-761.

37-MM.  AUTOMATIC GUN

        It was stated that the new 37-mm. automatic gun will soon be installed forward of the C/T in addition to the gun now fitted on Platform II.

        The ammunition for the new automatic gun can also be used on the old type 37-mm. gun.

PRESSURE TESTING

        When U-761 was at the Deutsche Werke, Kiel for her final overhaul in June 1943, her tanks were pressure tested.

        A captured document lists the following pressures:

Diving tanks, main ballast and reserve fuel oil tanks	6 kg/cm2
Interior negative buoyancy tanks - regulating tanks	140 kg/cm2
Fuel oil tank No. 2	8 kg/cm2
Waste water tank No. 2, port	5 kg/cm2

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PIPING TESTING PRESSURES

        The following refers to a U-boat built at Wilhelmshaven, but not necessarily to U-761 (from a captured document).

Cooling water lines	10 kg/cm2
Lubricating oil suction lines	4 kg/cm2
Lubricating oil pressure lines	5 kg/cm2
Diesel oil pressure lines	600 kg/cm2
Diesel oil suction lines	4 kg/cm2
Starting air lines	50 kg/cm2

PASSAGE THROUGH GIBRALTAR

        Commander-in-Chief U-boats recommended that U-boats pass through the Strait of Gibraltar by attaching themselves, if possible to an Allied convoy.  It was stated that 2 U-boats had used this method successfully.

        The suspected presence of underwater listening gear was reported to have prevented U-761 from attempting to pass through the Strait of Gibraltar at a greater depth than an average of 50 meters.

WALTER BOATS

        The Blom & Voss yard at Hamburg was said to have stopped building 500-ton U-boats and to be building Walter-boats.

        Another prisoner spoke of small boats which are similar, if not identical, with Walter-boats.  They are "Speer" boats.

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        Both Walter-boats and Speer-boats were described as single-drive boats (Einheitsantreib), using as fuel a powder mixed with sea water.

        It was stated that on a Walter-boat the engineer officer is personally at the hydroplanes when the boat is submerged.

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CHAPTER IV.  CREW OF U-761

COMPLEMENT

        U-761's crew totaled 52 men, divided as follows:  4 officers; 15 petty officers, averaging 25-1/2 years; 33 enlisted men, averaging just over 21 years.

OFFICERS

        The commanding officer of U-761 was Oberleutnant z.S Horst Geider, 26 years old, of the 1937 A term.  His entry into the U-boat arm was probably influenced by the fact that his father-in-law had served as boatswain on the World War I U-boat commanded by Grand Admiral Dönitz.  Geider knows Dönitz and has the highest respect for him.

        After serving as second watch officer on U-73 under command of Kapitänleutnant Rosenbaum and making 2 North Atlantic patrols, Geider took command of U-61, a school boat at Pillau.  He served on her for about a year and subsequently was appointed to the command of the then building U-761 which he commissioned 2 December 1942.

        Geider was quite difficult in conversation despite the fact that his political views were not at all radical.  He was lacking in color and personality and was not highly regarded by his men who thought that he was too cautious.  For example it was cited that he considered it foolish and unnecessary to raise the periscope while in the Strait of Gibraltar.  The

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discovery of U-761 was laid to this act.

        The executive officer of U-761 was Oberleutnant z.S. Wolfgang Benzine, 23 years old, of the December 1939 term.  He came to U-761 prior to the commissioning.  His commander described his political attitude as monarchist ic though not markedly expressed.  He was security-conscious.

        The second watch officer was Leutnant d.R. Friedrich Puppele, 22 years old, a lower deck promotion.  He had entered the Navy in 1940.  He came to U-761 at the commissioning.

        The engineer officer was Oberleutnant (Ing.) Karl Lendle who died at the sinking.  He came to U-761 27 October 1943 while the U-boat was at Trondheim, Norway.  He succeeded Oberleutnant (Ing.) Ammon.

        Lendle's career is unknown, but it was stated that he was engineer officer on a U-boat which sank in the Baltic.  The crew of this unidentified boat was saved, and Lendle escaped from a depth of 50 maters.  He was well liked by all the engine room personnel.

        Lendle's predecessor was Leutnant (Ing.) Fritz Ammon.  From the start Geider took a dislike to him, but it was said that the feeling was mutual.  The dispute broke into the open when U-761 was in Trondheim September 1943, and Ammon was court-martialed as the result of using insulting language.

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PETTY OFFICERS

        Among the petty officers were several who had made patrols on various other U-boats including boats which had operated in the Mediterranean.  In general, they responded well to the interrogator's efforts, and their experience led to almost all the worthwhile items of the report.

ENLISTED MEN

        Most of the enlisted men had participated in both patrols of U-761 but their knowledge was slight and their security-consciousness was as usual higher than that of their petty officers.

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CHAPTER V.  EARLY HISTORY OF U-761

COMMISSIONING.

        U-761 was commissioned at Wilhelmshaven 2 December 1942.

TRIALS AND EXERCISES.

        A few days later U-761 proceeded through the Kaiser Wilhelm Kanal to Kiel where she was attached to the 5th Flotilla and underwent her acceptance tests.  It was here that her "Gema" radar set was installed.  Mid-January 1943, she proceeded to the eastern part of the Baltic for the usual trials and exercises at Danzig, Hela, Libau (where torpedo firing practice was held), and Gotenhafen.  Detached from the 5th Flotilla, she belonged to the 8th Flotilla while working up.

FINAL OVERHAUL.

        U-761 was not ready for her final overhaul until early June 1943.  The delay was partly due to Geider's illness in April 1943, partly to the many days spent idly in various ports waiting for schedules to be arranged.  Most of the crew got liberal leaves and few expressed eagerness to go on patrol any sooner than necessary.

        U-761 did not return to her building yard for the final overhaul but was ordered to the Deutsch Werke, Kiel.  Her superstructure was re-built:  Platform II was added and

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a quadruple 20-mm. mount was fitted.  Two single 20-mm. cannons were installed on Platform I.  Her 88-mm. gun forward of the bridge was removed.  Several prisoners stated that the long stay at Kiel was due to scarcity of labor.

PREPARATION FOR FIRST PATROL.

        The final overhaul was completed during the last days of August.  On 1 September 1943, according to a captured diary, preparations were begun for U-761's first patrol.  At 1300, fuel oil was taken on, and at 1600, torpedoes were stowed.  At 1000, 2 September, flak ammunition was loaded, followed at 1300 by provisions.  At 1630 the first trim test was held.

        On 8 September 1943 U-761 was ready to leave on her first operational patrol.

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CHAPTER VI.  FIRST PATROL OF U-761

KIEL TO TRONDHEIM.

        At 0805, 9 September 1943 U-761 left Kiel in company with an unidentified U-boat, escorted by two patrol vessels.  The next day Kristiansand was reached but after a short stay U-761 sailed on, leaving the other U-boat there.  After staying over-night at an unidentified Norwegian harbor, U-761 arrived at Haugesund 12 September.  Bergen was reached 14 September.  She left Bergen early 15 September and spending nights at Aalesund, Molde, and Kristiansand, arrived at Trondheim 18 September 1943.

AT TRONDHEIM YARD.

        U-761 was sent to the yard where minor repairs were immediately begun.  In addition, the new G.S.R. sets, Borkum, Naxos, and Wanz G-2 were installed over a period of time.  Furthermore, the non-radiating "Main" receiver was fitted.  

COURT MARTIAL OF ENGINEERING OFFICER.

        Some time after arrival at Trondheim the engineer officer, Leutnant (Ing.) Ammon, used vituperative language to Geider during the course of a social evening.  Feeling between the two had not been good ever since they had met prior to the commissioning of the boat and apparently liquor loosened Ammon's tongue.  Geider had his engineer officer arrested, and he was court-martialed 21 October 1943, punished

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with 3 months in jail, and reduced in rank.

PREPARATIONS FOR DEPARTURE.

        U-761 had been transferred to the harbor basin on about 7 October, but it was not until 27 October that the new engineer officer, Oberleutnant (Ing.) Lendle, arrived.  After he had familiarized himself with his new boat for about a week, U-761 made her first diving trials 4 November.  On 14 November she took on fuel oil, and during the next 2 days torpedoes and provisions were loaded.

DEPARTURE FROM TRONDHEIM.

        At 0930 17 November 1943 U-761 slipped her moorings and headed out on patrol.  She was escorted by a patrol vessel until about 1800.  Her course into the North Atlantic led her through the Rosengarten, which was passed without incident.

DESTROYERS AND HEAVY WEATHER.

        Sailing through a thick fog 23 November a destroyer was sighted at a distance of about 1,000 meters, but U-761 was able to make an undetected get-away.  During the next days the weather became worse until U-761 was caught in a heavy storm 29 November.  Geider, intent on hardening his crew, continued to run on the surface, thereby subjecting the bridge watch to a continual soaking.  On 1 December 1943 two destroyers exchanging blinker signals were sighted when U-761 surfaced within 500 meters of them.  Heavy seas, however,

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made escape possible.  The weather moderated the next day, and a notation in a captured diary records calm seas on 4 December.  Five men were injured during the stormy period; the shields on the quadruple 20-mm. mount were bent in such a way that it could not have been used had it become necessary.

U-761 JOINS A U-BOAT PATROL GROUP.

        On 3 December 1943 joined a group of about 30 U-boats patrolling between Iceland and Greenland.  U-761 was ordered to patrol a stretch of about 15 miles in one of the northern AK squares and her position was estimated at 60 N., 30 W.  (Note:  Numbers and commanding officers' names of U-boats in this group will be found in Chapter IX.)  The name of the group was said to be "Coronel".  Later it was split into group Coronel I and Coronel II;  U-761 was then a member of Coronel II.  The groups were formed in anticipation of Allied convoys but neither U-761 nor her neighboring boats sighted any shipping.

BALANCE OF FUEL OIL.

        On 5 December 1943 an entry in a notebook indicated that 78 tons of fuel oil remained in the bunkers.

BATTERY EXPLOSION.

        At 0025 17 December 1943 the forward battery on U-761 explode without, however, damaging the U-boat.  The cook who happened to be near was injured slightly when the

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cover to the battery compartment blew off.  A considerable amount of smoke prevented an immediate examination; the engineer officer was overcome by the fumes when he attempted to enter the compartment.  The explosion could not be traced to any one cause, but a contributing factor may have been incomplete ventilation due to heavy seas.  Unable to use the forward battery, U-761 was ordered to return to her assigned base at Brest to be attached to the 9th Flotilla.

RETURN TO BASE.

        After an uneventful trip U-761 arrived at Brest at 1000 26 December 1943.  During the passage from Trondheim to Brest U-761 was neither attacked nor did she carry out any attacks.

        At 0900 30 December 1943 she went into dry dock remaining there until 21 January 1944 during which time various repairs and adjustments were made and her forward battery exchanged as well.  The quadruple 20-mm. mount was replaced with a new automatic 37-mm. gun on Platform II and her single 20-mm. cannons were replaced with twin 20-mm. cannons.

PREPARATION FOR NEXT PATROL.

        The following is an extract from a captured document:

27 January 1944		Took on fuel and lubricating oil
28 January 1944	at 0830	Stationa