Op-16-Z                                                                                                   S E C R E T
	Copy No.  ____
	NAVY DEPARTMENT
	OFFICE OF THE CHIEF OF NAVAL OPERATIONS
	WASHINGTON
	Final Report - G/Serial 32
	REPORT ON THE
	INTERROGATION OF SURVIVORS FROM U-575
	SUNK 13 MARCH 1944
	DISTRIBUTION:
	BAD
	BUORD
	BUSHIPS
	BUSHIPS (Code 515)
	BUSHIPS (Code 815)
	COMINCH (F-21)
	COMINCH (F-4253)
	COMINCH (F-45)
	COMINCH (FX-40)
	COMINCH (FX-43)
	COMNAVEU
	DNI (Ottawa)
	G-2 (Col. Jones)
	Op-16-1 via Op-16-1-F
	Op-16-1-V
	Op-16-FA-4
	Op-16-P
	Op-16-W
	Op-16-G
	Op-16-C
	SONRD
	C.O. Naval Unit, Tracy, Calif.
	Lt. J. I. Eibens (CSDIC, AFHQ)
	Lt. S. R. Hatton (CSDIC, AFHQ)
	Lt. (jg) R. J. Mullen (4th Fleet)
	Lt. V. R. Taylor
	Lt. J. T. Rugh, Jr. (JICA ME)
	1 May 1944
	S E C R E T

 

	S E C R E T
	TABLE OF CONTENTS
	Page CHAPTER I.   INTRODUCTION 1         II.   DETAILS OF U-575 3         III.   METEOROLOGICAL INFORMATION 17         IV.   GUNNERY 24         V.   TORPEDOES 28         VI.   COMMUNICATIONS 34         VII.   OTHER U-BOATS 36         VIII.   MISCELLANEOUS REMARKS 50         IX.   BASES AND FLOTILLAS 52         X.   CREW OF U-575 56         XI.   EARLY HISTORY AND FIRST SIX PATROLS OF U-575 62         XII.   SEVENTH PATROL OF U-575 68         XIII.   EIGHTH PATROL OF U-575 74         XIV.   NINTH PATROL OF U-575 79         XV.   TENTH AND LAST PATROL OF U-575 85         XVI.   SINKING OF U-575 92           ANNEX A.   CAPTURED NOTEBOOK           B.   CREW LIST OF U-575 AND U.S. EQUIVALENT OF GERMAN NAVAL RANKS
	S E C R E T

 

	S E C R E T
	ILLUSTRTATIONS
	Plate A Schnorchel       Plate B Naxos Aerial       Plate C Thetis       Plate D Attacks on 7th Patrol of U-575       Plate E Eighth Patrol of U-575       Plate F Ninth Patrol of U-575       Plate G Last Patrol of U-575       Appendix A Diagrams From Captured Notebook          (Plates 1 to 12)
	S E C R E T

 

	S E C R E T
	CHAPTER I.  INTRODUCTION
	U-575, a 500-ton U-boat under command of Oberleutnant z. S. Wolfgang Boehmer, was sunk on 13 March 1944 in position 46.10 N., 27.34 W. by destroyers and planes from T.G. 21.11.  Planes from U.S.S. BOGUE detected the presence of a U-boat at 1510 by means of sonobuoys and also by sighting an oil trace being left by the U-boat.  Sound contact was then made by U.S.S. HAVERFIELD, which was joined about an hour later by U.S.S. HOBSON and H.M.C.S. PRINCE RUPERT.  Depth charge and hedgehog attack forced the U-boat to the surface at 1838.  Shell fire from the destroyers and rockets from planes from U.S.S. BOGUE completed the destruction of the U-boat.
	The U-boat was abandoned immediately after surfacing, nearly all of the crew succeeding in leaving the boat.  Some were killed by gunfire while abandoning ship or while in the water.  Fourteen survivors, including two officers, were picked up by H.M.C.S. PRINCE RUPERT and brought to St. Johns.  They were here transferred to H.M.S. NENE, which brought them to this country for interrogation and internment.  Twenty-four survivors, including the commanding officer, were picked up by U.S.S. HOBSON, and taken to Casablanca.  One prisoner died on board from wounds sustained while abandoning ship and was buried at sea.  Three others were hospitalized in Casablanca.  The remainder were given preliminary interrogation in Casablanca, then put aboard U.S.S. ALBEMARLE, which brought them to the United States for further interrogation and internment.
	All the prisoners praised the treatment received aboard
	- 1 -
	S E C R E T

 

	S E C R E T
	the various ships.  Careful handling of the prisoners resulted in making the task of interrogators easier then it would otherwise have been.  Prisoners demonstrated only average security consciousness, and a few were willing to cooperate completely with interrogating officers.
	Special features of this report are:
	1.  Description of extensible Diesel intake and exhaust (Chapter II).
	2.  Description of R.D.S. (Chapter II).
	3.  Meteorology (Chapter III).
	*  Equivalents of German rank will be found in Appendix B.
	- 2 -
	S E C R E T

 

	S E C R E T
	CHAPTER II.  DETAILS OF U-575
	DISPLACEMENT
	500-tons.
	TYPE
	VII C.
	BUILDING YARD
	Blohm and Voss, Hamburg.
	COMMISSIONING
	19 June 1941.
	FLOTILLA
	7th at St. Nazaire.  U-575 was once a guest boat at Lorient.
	COVER NAME
	Lilliput.
	FIELD POST NUMBER
	M-44068.
	PATRON
	Dornbirn in Tirol.  This town was visited by some of the crew in spring or summer of 1942.
	VISUAL CALL SIGNAL
	X D C.
	- 3 -
	S E C R E T

 

	S E C R E T
	INSIGNIA
	Conning tower:  Insignia of the 7th Flotilla:  Bull of Scapa Flow.  Some of the crew recently took to wearing the figure of a Lilliputian on their caps.
	CONSTRUCTION
	Normal construction of the Blom and Voss 500-ton series.  Modifications since construction of U-570 (now H.M.S. GRAPH) may be found in Appendix A.
	DEPTH GAUGES
	(1)  One Papenburg gauge, 0 to 18 meters in control room.
	(2)  One gauge, 0 to 25 meters in control room.
	(3)  One gauge, 0 to 200 meters in control room.
	(4)  One gauge in stern compartment, 0 to 200 meters.
	(5)  One gauge in bow compartment, 0 to 200 meters.
	(6)  One gauge on starboard side in Diesel room, 0 to 25 meters, especially provided for use while proceeding at periscope depth with extensible Diesel intake mast raised.
	MAXIMUM DEPTH
	On her eighth patrol, U-575 went to a depth of 230 meters.  This is the greatest depth that could be ascertained.
	BRIDGE ARMOR
	16-mm. thick.  So equipped on ninth and tenth patrols.
	- 4 -
	S E C R E T

 

	S E C R E T
	AIR RAID SHELTER
	During lay-over period before the ninth patrol, two protected places were built into the enlarged bridge.  One on the starboard side provided shelter for three or four men.  One on the port side, large enough for one man.  During the lay-over preceding the tenth and final patrol, the coning tower was again modified, restoring more or less the old narrower shape.  Armored shelter for one man on port side was retained.
	GUN PLATFORMS
	See Chapter IV.
	TORPEDO TUBES
	Five; four forward, one aft.  Four new bow tubes installed before eighth patrol.  All tubes were of bronze.
	TORPEDOES
	See Chapter V.
	S.B.T. (Submarine Bubble Target)
	Fitted, but apparently never used.
	D.C.P.  (Depth Charge Plotter)
	Not fitted.
	- 5 -
	S E C R E T

 

	S E C R E T
	DIESELS
	G.W.  After nine patrols, both Diesels were removed and replaced by new ones.  Both the new and the old were G.W.  The new ones were not reversible.
	Revolutions and speeds normal.
	On her last patrol, U-575 was equipped with the "Schnorchel", which enabled the boat to travel on Diesels at periscope depth.
	SCHNORCHEL
	This device permitted the U-boat to proceed submerged at 13-1/2 meters depth on both Diesels at slow speed ("Langsame Fahrt"), i.e., 6 or 7 knots, while charging batteries.  U-575 proceeded through the Bay of Biscay submerged and on her electric motors during the daylight hours.  At dusk she came to periscope depth and raised her Schnorchel.  It is not necessary to surface entirely before raising the Schnorchel.  She proceeded in this fashion until about 2300, then surfaced for long enough to complete charging of batteries,  U-575 would run again on Schnorchel for a few hours just before dawn.  On top of the Schnorchel was a drum-shaped aerial ("Runddipol"), and during the entire time that the U-boat was proceeding on Schnorchel a watch was kept on the Wanz (as also, light conditions permitting,
	- 6 -
	S E C R E T

Click here to view Plate A:  Schnorchel-U-575  Extensible Diesel Intake and Exhaust

	S E C R E T
	on the periscope).  The schnorchel is streamlined in shape like a stack on a modern merchantman; the forward part being round, the after part pointed.  It stands just forward of the conning tower on the port side, and, when not in use, is lowered forward into a groove in the deck grating.  Raising and lowering are controlled by hand wheels in the control room which activate a hydraulic mechanism.  One hand-wheel is turned to "Open" for raising; when the schnorchel is to be lowered, this wheel must be on "Closed" and the other wheel turned to "Open".  The exhaust pipe, approximately 20 cm. in diameter runs up the inside of the Schnorchel to within one to one and a half meters of the top.  There it emerges and projects aft for about 40 to 50 cm.
	The drawing of the Schnorchel included in this report was made from description furnished by various prisoners from U-575.  The exactness of all details cannot be guaranteed, but it is believed largely correct.
	Prisoners' reactions to the Schnorchel were all of a pattern:  Every one objected to its use and hoped that it would be discarded.  Some feared the sudden creation of a vacuum in the U-boat if a wave should wash over the top of the intake mast; some complained of fumes in the Diesel compartment, caused by insufficient exhaust; all feared that in a phosphorescent sea they could be easily detected by enemy aircraft, and would rather proceed submerged.
	- 7 -
	S E C R E T

 

	S E C R E T
	An officer, however, discounted all possibility of a vacuum being caused by inadequate air intake, although during trials considerable fumes formed in the Diesel compartment.  This, he said, did not occur on patrol because the Diesels would only be run for a short time, then the U-boat would be thoroughly aired before the Diesels were started again.  No water ever entered the air intake he asserted.
	A radio rating objected to the Schnorchel because, he said, it interfered with listening on the multi-unit hydrophones, especially aft.  It was impossible to pick up sounds of any but the greatest intensity at a safe distance.
	During the last patrol the Engineer Officer sent two or three messages to Control, reporting U-575's experience with the new device.  In one report he declared that the pressure on air-intake was greater than he expected, judging from experience during trials at base and in Germany.  In another report he suggested an automatic depth-keeping apparatus to be used in conjunction with the Schnorchel.
	SUPERCHARGERS
	"Kapselgebläse".
	FUEL CAPACITY AND FUEL CONSUMPTION
	Normal.
	- 8 -
	S E C R E T

 

	S E C R E T
	MOTORS
	B.B.C.  Revolution and speeds normal.
	SWITCHBOARD
	B.B.C.
	BATTERIES
	Two banks of 62.  Lead-acid type.  Capacity, approximately 10,000 ampere hours.  Maximum diving angle possible without spilling stated to be 480.  Endurance at flank speed, stated to be 1.5 hours.
	ROTARY CONVERTERS
	One 0.3 K.V.A.
	One 6 K.V.A.
	One 1.5 K.V.A.
	One transmitter converter.
	Converters for gyro compass, torpedo fire control, echo-sounder.
	COMPRESSORS
	One Junkers and one E-Verdichter.
	COMPRESSED AIR FLASKS
	Six groups of 2 bottles @ 360 liters.
	OXYGEN SUPPLY
	Six flasks, four in control room, two in Petty Officers' quarters.  (One prisoner said 10, distributed as
	- 9 -
	S E C R E T

 

	S E C R E T
	follows:  Four in control room, 3 in bow compartment, 1 in stern compartment, 2 in Diesel room.
	PUMPS
	One main and one auxiliary ballast.
	GERMAN ASDIC
	Not fitted.
	G.S.R.  (German Search Receiver)
	Wanz G-2, Naxos, and Borkum.  Demountable aerial for Naxos (see sketch), and drum-shaped aerial for Borkum and Wanz.  Additional drum-shaped aerial on top of Schnorchel.
	RADAR
	Not fitted.
	R.D.B.  (Radar Decoy Balloons)
	Three or four boxes of balloons, 30 per box.  Stored, one in control room,. others in bow compartment.  These were used 4 or 5 times on last patrol when a shadow was sighted or a G.S.R. warning was received.
	R.D.S.  (Radar Decoy Spar Buoy)
	On her last patrol U-575 carried 15 Radar decoy buoys known as "Weihnachtsbaum" (Christmas tree) and as "Thetis."  These buoys were carried dismantled in the bow compartment.  One such buoy consists of a cork float and two hollow rods approximately two meters in length.  Assembly usually takes place in the conning
	- 10 -
	S E C R E T

Click here to view Plate B:  Naxos G.S.R. Antenna U-575

	S E C R E T
	tower, and one set can be assembled in four minutes.  Each of the hollow rods contains one actual Radar Decoy mast which is removed.  The two rods are then fastened together, end to end, with a cotter pin and fastened on like manner to the cork float.  The two Radar Decoys are then likewise fastened together and in turn mounted onto the cork float.  The rods are open at the bottom so that they fill with sea water.  The masts are made of wood.
	These details may be observer on the drawing made by a prisoner.  Note, however, that while the drawing is generally speaking correct, the groups of Dipoles are in sets of six and not in sets of three as indicated.  Of these six, three point upwards and three point downwards each at different angles.  They are all of the same length, i.e., 40 cm.
	R.D.S. are believed to be very durable.  While and R.D.S. will drift considerably, it is felt that it could survive a considerable length of time - - even as much as six months under favorable weather conditions.
	Prisoners state that all U-boats now leaving Biscay ports carry a number of these decoys and scatter them throughout the Biscay area.  U-575 surfaced every night and laid a total of ten on her outward voyage.  The rest were to have been laid in the same area on her return voyage.  One prisoner said that the idea is "to plant
	- 11 -
	S E C R E T

Click here to view Plate C:  Thetis - Radar Decoy Buoy - U-575

	S E C R E T
	the Bay of Biscay full of them".  They are not intended to be used in operations against convoys.  It was stated, however, that on receipt of special orders from Control, such buoys might be launched in areas other than the Bay of Biscay:  for example, for the purpose of confusing ship and plane radar during operations against convoys.
	It is believed by prisoners that R.D.S. are effective against both surface ship radar and A.S.V. and that varying angles at which the Dipoles are placed would provide targets for different frequencies.
	D/F GEAR (Direction Finder)
	Standard D/F gear, as well as HF/DF.  The latter was never used, as the voltage regulator did not function satisfactorily.
	TRANSMITTERS
	Two.  One 200 watt Siemens, one 40 watt Lorenz emergency.
	RECEIVERS
	One "Main" receiver.  One all-wave receiver.  One short-wave receiver.  An additional all-wave receiver exclusively for the use of the meteorologist was installed in the radio room before the last patrol.
	EXTENSIBLE ROD ANTENNA
	Fitted.
	- 12 -
	S E C R E T

 

	S E C R E T
	UNDERWATER TELEGRAPHY
	Fitted.
	WATCHES FOR RADIO PERSONNEL
	For the first part of the voyage:
	0800 to 1200
	1200 to 1600
	1600 to 2000
	2000 to 0200
	0200 to 0800
	During the course of the voyage changed to:
	0800 to 1400
	1400 to 2000
	2000 to 2400
	0000 to 0400
	0400 to 0800
	HYDROPHONES
	Fitted, normal multi-unit type (G.H.G.)
	MAGNETIC COMPASS
	One in control room forward.
	GYRO COMPASS
	One in control room aft.
	GYRO REPEATERS
	One on the bridge, two in control room, one in conning tower, one in listening room, one on D/F gear in radio
	- 13 -
	S E C R E T

 

	S E C R E T
	room.
	T.D.C.  (Torpedo Data Computer)
	Normal older type.  Angle-of-impact switch built in at an undetermined time before the eighth patrol.
	ELEKTROLOT
	Fitted but never used.
	ECHO SOUNDER
	Atlas.
	AIR PURIFICATION
	Carried about 200 potash cartridges.
	LIFE RAFTS
	Fourteen or 15 one-man rubber boats stowed on bunks:
	Two boats of 3-meter size, one in motor room, one in Petty Officers' quarters; one boat of 4-meter size in bow compartment; three rafts similar to "Marx Rettungsinsel" in control room.
	LIFE JACKETS
	Fifty-four, one for each man.
	ESCAPE LUNGS
	Fifty-five, one for each man and one extra.
	DIVING APPARATUS
	One simple suit with oxygen tube but without helmet,
	- 14 -
	S E C R E T

 

	S E C R E T
	for shallow depths.  To be used only for clearing fouled rudders or hydroplanes, or making minor emergency repairs.
	VISION AIDS
	Carried polarized glasses for day use and red glasses for aiding night vision.  Every man who needed a pair had his own.
	MEDICAL SUPPLIES
	The Pharmacist's Mate 2/c stated that a complete kit for any injury was supplied.  An operation for appendicitis could have been performed on board if necessary.  Vitamins supplied and given to crew as part of their diet.
	WEATHER BUOYS
	Not carried.
	WEATHER BALLOONS
	Forty of Radiosonde type for measuring temperature and pressure.  These differ from the type used on land in that they have no provision for measuring humidity.  The meteorologist explained this fact by saying that a second trained listener, not usually available on a U-boat, is necessary to receive humidity data.  The transmitters for these balloons were stored in two boxes in the bow compartment, the balloons themselves
	- 15 -
	S E C R E T

 

	S E C R E T
	in a chest in the officers' quarters.
	Hydrogen supply for the weather balloons and for R.D.B. was contained in three large flasks on upper deck.
	For further meteorological data see Chapter III.
	- 16 -
	S E C R E T

 

	S E C R E T
	CHAPTER III.  METEROLOGICAL INFORMATION
	The following information was given by the Meteorologist carried aboard U-575 on her tenth and last patrol:
	METEROLOGICAL BROADCASTS
	The principal meteorological broadcast stations are:  DDX, Nauen, which is principal transmitter for the German Air Force; and DAN, Norddeich, which is principal transmitter for the Navy.  There are a number of other smaller broadcast stations, but these are very short range and only serve a small local coastal area.
	Weather bulletins are broadcast continuously by all stations on a special frequency which does not change.  In addition to DAN, approximately ten other German Navy stations transmit these bulletins, a special time of day being assigned to each area.
	Broadcasts contain weather report, analysis of weather maps, upper air data, and forecasts.  The broadcasts are drawn up according to the standard "Copenhagen" system and this is re-encoded with numbers which change frequently.  This applies to the Navy.  The German Air Force uses another system which this prisoner claimed not to know.
	The standard times of weather observations are as in peace time, and according to the international system.  However, the hours used are German Summer Time.
	ATLANTIC AND NORTH AMERICAN AREA.
	Formerly data was made available to all weather stations
	- 17 -
	S E C R E T

 

	S E C R E T
	from meteorological groups operating in Greenland.  This is no longer the case.  The U-boat high command is regularly supplied with weather reports from operating U-boats.  (See entry on U-552 in Chapter VII).
	WEATHER MAPS
	In German weather stations, a minimum of two weather maps must be drawn each day, and usually three are drawn.
	ACCURACY OF FORECASTS
	The prisoner claimed an average accuracy of eighty percent.
	WEATHER RECONNAISSANCE FLIGHTS
	Weather reconnaissance flights are regularly made by aircraft, and observations are circulated to all stations in clear by teletype.
	IRISH SOURCES
	The prisoner has never heard of any weather reports received from the Irish or from German sources in Ireland.
	WEATHER REPORTS FROM SUBMARINES
	All U-boats are supposed to include a short weather signal in each transmission they make.  However, in view of the danger of transmissions being D/F'd, U-boat commanders are very reluctant to make their messages any longer than absolutely necessary.  Therefore, they often fail to include weather data, but of course would furnish it when called upon by Control to do so.  From the data furnished by
	- 18 -
	S E C R E T

 

	S E C R E T
	U-boats, headquarters makes an analysis which is included in its transmission both by teletype and broadcast.
	U-575 carried 40 balloons fitted with automatic transmitters, which transmitted temperature continuously, the curve being registered on a special teletype instrument attached to an all-wave receiver, as well as barometric pressure at five minute intervals.  Sling-type thermometers and psychrometers, barograph, hypsometer for checking the barograph, and anemometer were carried, as well as a number of ordinary thermometers for checking water temperature.
	U-boats normally carry two barometers, one in the control room and one in the radio room mounted on shelves on a bulkhead.  U-575 carried an additional one similarly mounted in the Captain's cabin.
	LONG RANGE WEATHER FORECASTING
	Long range weather forecasts are made only by a Professor Bauer at Bad Hamburg.  Such forecasts are made for two-week periods.  The prisoner could not state what success long range forecasting has had.
	METEOROLOGICAL OFFICERS
	Meteorological officers are attached occasionally to U-boats, always to Raiders and to large units from cruisers on up.  Meteorological officers are attached to every airport, one officer to a "Geschwader".  In the Army, meteorologists are attached only for ballistics purposes.  A chief meteorologist is attached to Hitler's headquarters.
	- 19 -
	S E C R E T

 

	S E C R E T
	PLANNING MILITARY OPERATIONS
	Considerable attention is paid to the effects of weather in planning military operations as, for example, in the case of the Channel dash by SCHARNHORST and GNEISENAU.
	METEOROLOGISTS AND CHEMICAL WARFATE
	This prisoner had a course of training in meteorology in relation to Chemical Warfare.  The course of instruction was based on British documents captured at Crete.
	METEOROLOGICAL ORGANIZATION
	Approximately 150 officers and 1500 men in the German Navy have been trained for actual daily service at observatories.  This is exclusive of about 1,000 men and 200 to 300 officers attached to the headquarters at Greifswalde.
	Candidates for the service are selected because of previous experience and suitable background, such as mathematics, geographers, physicists, etc.  Some volunteer for the service, others are drafted.  Naval meteorological officer candidates are educated at the University of Berlin where the shortened war-time course takes seven trimesters.  This is followed by a year at Gotenhafen or some other Baltic station for post-graduate training.
	After completing post-graduate training, meteorologists are then usually assigned to one of the regular meteorological stations.  The entire peace-time set-up is maintained.  Subsequently meteorologists may be assigned to U-boats, cruisers, or Raiders.  The same system
	- 20 -
	S E C R E T

 

	S E C R E T
	applies to meteorologists for the Air Force and the Army.  These are, however, trained in other universities.
	Typical routine in a meteorologist's office:  Radio personnel, map maker, and teletype operator report for the first weather map which is as of 0200.  A forecast is made from this chart.  Charts as prepared and are ready between 0500 and 0700.  One Petty Officer is kept on a watch system of six hours on and six hours off -- 24 hours a day.  During the night hours one meteorologist officer is on sleeping watch.  The second weather chart is made as of 0800.  This is ready at about 1500 including all last minute additions.  No forecast is made with this chart.  The third chart is made as of 1400 and is ready at 1700.  A forecast is made with this chart.  At 1900 the meteorologists will add in to his charts reports from surrounding areas.  Equipment of a meteorological station consists of thermoscreen with all equipment, teletype, and radio station for receiving messages in case the teletype breaks down, and otherwise all standard peacetime equipment only.
	PERSONALITIES
	The prisoner had a meteorological course under Dr. Wagemann, from January to March 1943.
	Professor Bauer uses Multiple Correlation Method in long-range forecasting.  Dr. Wagemann has another method, which is not known to the prisoner, as Wagemann does not instruct in long-range forecasting.
	- 21 -
	S E C R E T

 

	S E C R E T
	Professor Weikmann is chief of the Leipzig school of Symmetry Points.  This school is only for the Luftwaffe.  The course takes two trimesters.
	CORRELATION AND SYNOPTIC TECHNIQUE
	Correlation and Synoptic Technique is part of course in Geophysics and Statistics given at each university.  All meteorologists must take two trimesters in Statistics and two trimesters in Synoptic Technique.
	BALLOONS USED AT SEA
	Balloons used are radiosonde type.  Air mass analysis results from data transmitted from the balloons.  No other means of making measurements of temperature over sea were known to the prisoner.
	FRONTAL LOCATION
	Use of RD/F in connection with Frontal location has proven unsuccessful.
	METEROLOGIST'S ACTIVITIES ON LAST PATROL
	The prisoner stated that the Captain was under special orders to regard this patrol not as a regular war patrol but as one for weather study only.  He was ordered to a certain operational square northwest of the Azores.  When he had reached this square, he was to report his position and stand by for specific instructions for the meteorologist, which instructions would at that time be radioed