U-23 - 7th War Patrol

Translation by Jerry Mason with help from Andi Forster

Departed	Date	Arrived	Date	Days at Sea
Wilhelmshaven	18 January 1940	Wilhelmshaven	29 January 1940	12

 

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Ships Hit
Date	KTB Time	Position	Ship	Tons	Nationality	Convoy
24 Jan 40	19.08	59°27'N, 0°18'W	VARILD	1,085	Norwegian
			Total = 1,085
Note:  The positions in the table above and in the Google Earth patrol summary are derived from the KTB and in many cases do not match those set forth in authoritative references such as Jürgen Rohwer, Axis Submarine Successes of World War Two or the Uboat.net website.  The goal here is to present the picture relative to the U-boat and not the absolute position that the ship was attacked or sank.

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			K  r  i  e  g  s  t  a  g  e  b  u  c  h    "  U  23  "
			=o=o=o=o=o=o=o=o=o=o=o=o=o=o=o=o=
			Kommandant  :  Kaptlt.    K  r  e  t  s  c  h  m  e  r  .
			Beginning:          18.1.1940
			Concluding:        29.1.1940.
				© U-boat Archive 2023 - all rights reserved

Click the flag to view the above page from the original German KTB

	- 1 -
		18.01.40
		15.55		Cast off from U-boat harbor Wilhelmshaven.  From the lock proceeded behind ship of the line"SCHLESIEN" as ice assist.
		19.07		Passed Lightship F outbound.
				Detached from "SCHLESEIN".  Continued on Route "blau".
		19.45		Recognition Signals exchanged with own patrol boat.
		20.00	L 2479 upper-left
			SSE 3, Sea 3, overcast, Vis. medium, wind increasing
		19.01.40
		00.00	L 2733
		04.00	L 2789
		08.00	L 2794
		08.30		Dived.
		12.00	L 2846 lower-right	Transit submerged by day at periscope depth.
		16.00	L 2847
		17.10		Surfaced.
		20.00	E 2942 lower-right corner
		20.01.40
		00.00	E 2767 lower-center edge
		04.00	E 2531 lower-left
			SSE 4, Sea 3, overcast, from time to time moon, Vis. good
		08.00	E 2234 upper-center
		09.02		Dived.
		09.12		Surfaced.
		12.00	E 2058 lower-center edge	Day's run 180 nm.
		16.00	E 1822 lower-left
		20.00	E 1646 lower-center
		22.00	E 1587 left edge upper	Miss on merchant steamer (1000 tons).
		21.01.40
		00.00	E 1470 lower-left corner
		04.00	E 1234 center
		05.42	E 1175 center-left edge	Miss on merchant steamer.
		07.50	E 998	Darkened tanker, that initially had its side lights set, came in sight on southerly course.
		08.00	E 1058
				Came to southerly course at AK to move ahead, but that had to be given up due to lightness.  At the same time the steamer extinguish its lights and came about, so apparently positioned there moving back and forth.

	Sun and Moon Data 18.01.40
	Sun and Moon Data 19.01.40
	Sun and Moon Data 20.01.40
	Sun and Moon Data 21.01.40

	- 2 -
		continued
		21.01.40		It was was probably a U-boat trap.  Because there is only one torpedo in the tubes, dived to load the 2 reserve torpedoes, to continue the attack during the day.
		08.45
		11.00		Depth charge detonation about 5 nm away.
		11.30		Depth charges now closer, ran off at listening speed to the east course at depth 50 meters.
		12.00	E 1177 upper-center edge	Day's run 189 nm.
		13.00,	)
		15.00 and	)	Further depth charge detonations in the vicinity.
		17.15	)
		16.00	E 1237 upper-right corner	In the G.H.G. at irregular intervals perceived a rising and falling whistle tone, which has not been encountered thus far.  (Duration about 1-2 seconds.)
		18.15	SSW 1-2, Sea 1-2, Vis. good, moonlit	Surfaced and ran to the north. With this, the gyro-compass had been switched off during the listening cruise and the magnetic compass was not useable because of the [electrical] charge, took the North Star ahead, until at 21.45 hours when the gyrocompass settled down.  Thereafter course for the north tip of the Shetlands.
		20.00	E 1299
		22.01.40
		00.00	E 1245 center-left edge
		04.00	E 1009	Gyro-compass out of service.  Magnetic compass also cannot be used due to geomagnetic interference.  After getting land in sight headed for Sullm Voe.
			E 1, Sea 0, Vis. good, moonlit, at times clouds
		08.00	E 827 lower-right corner
		08.25		Dived in the entrance to Yell Sound.  Approaching aircraft from the south, type Fairey Seafox, altitude 300-400 meters, apparently comes out of Yell Sound.
		10.30		Off Burra Voe put the boat on the bottom in depth 29 meters.
				Gyro-compass repairs.
		12.00	Burra Voe in Yell Sound	Day's run 126 nm.
		16.00	-""-	With the prevailing cloudless weather it was now impossible to proceed on the surface at night because of the moonlight (2 days before full moon).  There was also the fact that the land was covered with snow and silhouettes stand out very clearly.
		18.20	Yell Sound, Shetlands	Therefore raised the boat from the bottom and ran to the south submerged in the west channel of Yell Sound, to penetrate Sullom Voe and attack the warships suspected to be there.  With the very bright night suspect the visibility will be sufficient.
		19.54 - 19.55	NNW 2-3, moonlit, isolated clouds, Vis. very good, clear air, snow covered mountains	West of Lamba Isle surfaced momentarily to orient myself.
		20.00	E 825 upper-center	Boat is prepared for destruction.

	Sun and Moon Data 21.01.40
	Sun and Moon Data 22.01.40

	- 3 -
		continued
		22.01.40		Broke off the operation in the entrance to Sullom Voe, because further penetration is impossible due to nets and behind them patrol vessels lying at anchor.
				Barrier gap could not be distinguished.  Nets run from the NW headland of the Orka Peninsula (Calback Ness) in a westerly direction to the SE headland  of Gluss Isle.  The net buoys are larger than similar German ones.  The barrier vessel was anchored south of it on the east side of the entrance and was darkened.  Further in the interior of Sullom Voe there was good visibility and a good background, but it was not possible to see into Scatsta Voe and Garths Voe, no vessels could be made out.
				A land reconnaissance of the inner bay of Sullom Voe and the net barrier from the level of the Orka Peninsula was refrained from because of the extremely unfavorable lighting conditions for surfacing. Such an operation would be promising in the new moon period.
		21.42		Moved off to the north in the west channel up to Lamda Isle initially submerged, then surfaced.
		22.15		Crash dive due to a fishing vessel, that came around Muckle Holm heading directly towards the boat.
		22.24		Surfaced.
				In contrast to earlier, the northern part of the Yell Sound there was only a small fishing cutter, no more large patrol vessels.
				The lit buoys reported earlier were no longer out.
				Due to oncoming west weather conditions I decide, to go to the east coast of the Shetland Islands and explore a few bays and roadsteads in the lee.
				In the waters of the Shetlands, deviations occur in the magnetic compass that were considerably larger than the usual misdirections.  They can be traced back to disturbances of the earth's magnetic field there.  In my opinion, it is of great importance to clarify whether and in what way these geomagnetic disturbances are an influence on the combat pistols of our torpedoes.
		23.01.40
		00.00	E 888	Passed Muckle Flugga and went to the south on the east coast.
		01.00		In the fjords and bays of the islands Unst and Fetlar no ships were encountered.  (In the bays from Burra Firth to the Wick of Tresta)
		04.00	E 946 center-right edge	At 04.00 hours the boat is 3 nm off the east entrance of Yell Sound, to be able to still

	Sun and Moon Data 22.01.40
	Sun and Moon Data 23.01.40

	- 4 -
		continued
		23.01.40		penetrate tonight between Heoga Ness and Lunna Holm and examine the bays on the NE side off the Mainland.  4 lighted patrol vessels cruise off the entrance.  In the very bright moonlit night and the very good visibility and despite a few hail squalls it was neither possible to get through to the west or stay a long time off the entrance.  Therefore, after a few unsuccessful attempts, I decided to break off the coastal operation, which could hardly be carried out in this weather condition, and move further away from land, initially to the east, then from 08.15 hours to the south.
				The strong guarding of the east entrance of the Yell Sound suggests that it is used far more often than the north entrance.
				The navigable waters east of Sullom Voe are considerably shallower than the northern ones and could therefore be more easily blocked by us with mines.
				The net barrier off Sullom Voe lies in such deep water that an immediate closure of this entrance with U-boat mines can be pictured.  However, I consider a penetration through the net barrier is possible after having previously informed myself by a reconnaissance from land (Orka or Gluss Isle) during the new moon period.
				All such coastal operations are made considerably more difficult if they are scheduled for the time of the full moon.  It is also not possible to take advantage of all the possibilities to bring about success, since the unfavorable conditions of the daytime still prevail as a result of the moonlight at night.
		08.00	E 1245 upper-left
		08.20		Dived.  Continued submerged.  Torpedo heating.
		12.00	E 1243	Day's run 114 nm.
		16.00	E 1242
		18.30		Surfaced.
		20.00	E 1180
			SSW 1-2, Sea 0, moon, hazy, increasing cloudiness
		20.20		Dived for night attack.  on steamer (about 1000 tons). Tube failure due to operational error, because the torpedo was driven too hard against the retaining bolt.  This jammed.  Malfunction was corrected by replacement of the retaining bolt
				Surfaced.  Maneuvered ahead again for 2nd shot.
		21.56	F 1361	Dive for attack.  Miss, because it was a circle runner by observation in the G.H.G.
		22.19		Surfaced.

Sun and Moon Data 23.01.40

	- 5 -
		24.01.40
		00.00	E 1299 upper-right
		04.00	E 1176 lower-right
		08.00	E 1173 lower-right
		08.49		Dived.
		12.00	E 1114	Day's run 85 nm.
		13.15		Depth charges at great range, propeller sounds bearing 320°T.  Nothing seen through the periscope at depth 10 meters despite clear visibility.
		16.00	F 1114 upper-center	Submerged transit.
		18.25		Surfaced.
		18.50		Dived for submerged attack on steamer (1500 tons).
		19.08	E 1115 lower-left	Hit center.  Steamer sank in 45 seconds.
				Ran off.
		19.10		Surfaced and moved back and forth in position off the SE coast athwart the observed steamer route.
		20.00	E 1055 lower-right corner
			NNE 3, Sea 2-3, Vis. good, overcast, in part full moon.
		25.01.40
		00.00	E 1057 upper-center edge	In sight of the Shetlands whose snow covered mountains stand out well in the moonlight.  Sumburgh Head Lighthouse burns with the correct identifier.  No Ness Island was seen for a short time as a darkened vessel.
		03.00	"        "        "
		04.00	E 998 upper-center.
		08.00	E 1115 lower-left
		08.20		Dived.  Proceeded submerged.
		12.00	E 1175	Day's run 74 nm.
		16.00	E 1235 lower-left
		20.00	E 1174 lower-left corner
			NNE 2, Sea 3-4, Vis. good, overcast, in part moonlit
		26.01.40
		00.00	E 1114 upper-center
		04.00	E 1113
		08.00	E 1114 upper-center edge
		08.25		Dived.
		09.30		Water was found in the equipment chamber of the last torpedo, therefore began return transit,
		12.00	E 1054	Day's run 75 nm.
		16.00	E 1054 lower-right corner
		17.55		Surfaced.  Continued transit on the surface.
		20.00	E 1291 lower-left
			ESE 5-6, Sea 5, overcast, Vis. medium
		27.01.40
		00.00	E 1409 lower-center edge
		04.00	E 1526 upper-right corner
		08.00	E 1704 upper-left

	Sun and Moon Data 24.01.40
	Sun and Moon Data 25.01.40
	Sun and Moon Data 26.01.40
	Sun and Moon Data 27.01.40

	- 6 -
		continued
		27.01.40
		12.00	E 1822 center-right	Day's run 105 nm.
		16.00	E 1941 lower-center
		20.00	E 2058 upper-right corner
		20.25	ESE 5-6, Sea 6, cloudy, in part moonlit, Vis. medium	Radio Message to F.d.U. West:  19.00 hours square E 2059 return transit.  Task broken off for the moment.  Net barrier.
		20.54		Radio Message from F.d.U. West:  Return harbor Wilhelmshaven.
		28.01.40
		00.00	E 2296 lower-left corner
		04.00	E 2472 center-right
		08.00	E 2589 upper-right	Dived, continued transit submerged.
		12.00	E 2708 lower-left	Day's run 127 nm.
		16.00	E 2767 center-left edge
		18.25		Surfaced.
		20.00	E 2824 upper-right corner
			ESE 4, Sea 6, overcast, Vis. medium
		23.33		Radio message to F.d.U. West:  Arrival 29 January 16.00 hours at Lightship Fritz.
		29.01.40
		00.00	L 2950 upper-left
		04.00	L 2944 lower-center
		07.50	L 2837	Passed 6 own patrol vessels at a distance of 4000 meters, without being noticed by them.
		08.06	L 2837 upper-right
		12.00	L 2681 center-left	Day's run 230 nm.
		15.15		Passed Lightship Fritz inbound.
		16.16		From Schillig Roadstead ice escort in tow Sperrbrecher and tug "GEIER".
		19.10		Made fast in the lock.
		20.45		Made fast at the U-boat Base pier.
			S  p  e  c  i  a  l    E  x  p  e  r  i  e  n  c  e  s  . ===============================   1.) Yell Sound.     Net barrier at the Sullom Voe entrance.  Net runs from the NW headland of the Orka Peninsula (Calback Ness) in westerly direction to the SE headland of Gluss Isle.     North entrance of the sound little patrolled.  The buoys observed earlier were no longer out.  East entrance strongly patrolled (fishing trawlers).   2.) Steamer tracks.

	Sun and Moon Data 27.01.40
	Sun and Moon Data 28.01.40
	Sun and Moon Data 29.01.40

	- 7 -
			2.) Steamer tracks.     a) SE tip of the Shetlands in direction 80° (to both sides).     b) South tip of Fair Isle in direction 90° (to both sides).     c) = 58°40'N, = 1°12'E in direction 100° to both sides.       In coastal waters the steamers mainly at night.       Sometimes ebb and flow of steamer traffic was determined.   3.) In the Shetlands - Fair Isle area daily, apparently haphazard depth charges were thrown.   4.) Light beacons of the Shetlands are extinguished.  On 25 January 03.00 hours Sumburgs Head Lighthouse burned with the correct identifier.

 

	Enclosures to U-23's KTB - click on the text at left to proceed to the document
Torpedo	Torpedo firing reports

 

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