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U-boat attacks on the convoy SC-48 and the mysterious loss of HMS GLADIOLUS during the night of 16/17 October 1941

by Rainer Kolbicz (January 2010 for uboat.net)

The British corvette HMS GLADIOLUS was reported missing after a night action fought between five U-boats and the escorts of convoy SC-48. When the Admiralty tried to investigate her loss during the war, there was not much they could find out. The last ship in radio contact with her was HMCS WETASKIWIN when they were together on station on the port side astern of the convoy at 19.30 hours GMT on 16 October. At 22.00 hours GMT, HMCS WETASKIWIN received a signal purporting to come from HMS GLADIOLUS requesting a signal for radar purposes on 325 k/cs. They doubted the authenticity of the signal, asked for identification but received no reply. Nothing was ever heard or seen.

When the German war diaries were examined after the war, no U-boat claim could be found that matched the loss of the corvette during the night in question. Furthermore the Allied reports for the night are incomplete, on one side because the ships of the convoy commodore and vice commodore were straggling and not present at that time and on the other side because the escorts were made up of vessels from four different nations that were not trained to co-operate with each other. To make things more confusing the senior officer (SoE) in command of all escorts changed shortly after the U-boat attacks had begun when the command was passed from the American Task Unit (TU) 4.1.4 to HMS HIGHLANDER after she joined.

On the afternoon of 16 October, convoy SC-48 consisted of 38 ships in 10 columns and was escorted by vessels of TU 4.1.4 and 4.1.15 consisting of five destroyers and four corvettes:

At 21.30 hours GMT, the convoy changed course to 90° directly towards the Mid Ocean Meeting Point (MOMP) where it was planned for Escort Group 3 to relieve the previous escort. Because the Asdic of HMCS BADDECK was out of order, she went on radar station ahead of the convoy for the night. The last ship of TU 4.1.4, USS GREER had not yet arrived at the convoy but was only a few miles astern. At 22.00 hours GMT, HMS HIGHLANDER and HMS BROADWATER were approaching the convoy from the north when the U-boat attacks on the convoy commenced. During the night, three corvettes (HMS ABELIA, HMCS PICTOU and HMS VERONICA) coming as reinforcement from convoy ON-25 reached the convoy SC-48 from astern.

Note: Unless otherwise stated the time used in this article is the German time as used by the U-boats during October 1941. This time was two hours ahead of Greenwich Mean Time (GMT), so 17/0000 German time is 16/2200 GMT.

U-boat attacks carried out on ships in convoy SC-48 during the night of 16/17 October 1941

Time U-boat Grid Target Weapon Observations
17/0000 U-553 AL 1962 Tanker, 6000 T (1) Missed
17/0004 U-553 AL 1962 Tanker, 6000 T (1) Missed
17/0005 U-553 AL 1922 Tanker, 6000 T (1) Missed
17/0007 U-553 AL 1922 Tanker, 6000 T (1) Hit amidships, sinking not observed
17/0128 U-558 AL 1966 Tanker, 7000 T (1) Missed, but observed detonation after 4 min. 47 sec. – assumed hit on ship beyond
17/0131 U-558 AL 1966 Tanker, 7000 T (1) Hit aft after 50 sec., tanker caught fire and sank fast by the stern
17/0149 U-558 AL 1966 Steamer, 6000 T (1) Hit after 49 sec., settled on even keel
17/0214 U-558 AL 1966 Steamer, 4000 T (1) Hit after 12 sec. with high column of smoke
17/0342 U-432 AL 0143 Steamer, 6000 T (1) Hit after 2 min. 30 sec. and sinking by stern
17/0343 U-432 AL 0143 Steamer, 5000 T (2) Missed, but observed detonation after 2 min. 55 sec. – assumed hit on ship beyond
17/0346 U-432 AL 0143 Steamer, 7000 T (1) Hit amidships after 1 min. 20 sec., broke in two and sank immediately
17/0400 U-432 AL 0143 Tanker, 12000 T (1) Hit aft after 41 sec., caught fire and stopped
17/0415 U-568 AL 0146 Destroyer, 1400 T (4) Hit after 1 min. 39 sec., broke in two and sank
17/0448 U-432 AL 0143 Tanker, 12000 Tf (1) Hit amidships after 31 sec., exploded and sank immediately
17/0538 U-553 AL 0143 Destroyer, Tribal T (2) Missed, surface runner
17/0602 U-568 AL 0155 Corvette T (1) Missed

Weapon: T = Torpedo, (n) = number of torpedoes fired, Tf = Torpedo (Coup de Grâce)

Four U-boats claimed seven merchants and a destroyer sunk and possible hits on two more ships. Confirmed from Allied reports is the loss of six merchants, the hit on USS KEARNY and the disappearance of HMS GLADIOLUS.

U-boat attacks on escorts during the night of 16/17 October

Claim: U-568 tried to overtake the convoy on its port side for several hours but each time a destroyer with two funnels, identified as of the A or D class, disturbed her approaches and a spread of four torpedoes was fired at the warship at 04.15 hours. They observed one hit after 1 minute 39 seconds and the subsequent sinking of the destroyer after it broke in two. Afterwards the U-boat reloaded the torpedo tubes but was located by a corvette at 05.40 hours. U-568 then tried to escape at full speed but the corvette was already too close, so the U-boat fired its stern torpedo at the warship following directly behind her but missed and had to crash dive.

Observations (Allied times in GMT):

17/0206USS KEARNY: Steadied ship on 240° and changed speed to 10 knots to avoid collision with a British corvette. Shortly thereafter with full left rudder, resumed swinging ship to port to parallel convoy course and take further action as necessary.
17/0210 USS KEARNY: A torpedo struck the ship amidships on the starboard side abreast of No. 1 fire room below the waterline. A torpedo wake was seen crossing the bow and another was seen crossing the stern.
17/0210 USS PLUNKETT: Ship torpedoed in 57°00N/24°00W.
17/0225 HMCS BADDECK: Sighted suspicious object on port side of convoy going with it. Turned around to investigate. It appeared to be a destroyer, probably USS KEARNY.
17/0225 USS KEARNY: HCMS BADDECK challenged and we replied, using a battle lantern.
17/0241 USS KEARNY: Radio communication was reestablished with the emergency radio. A message was sent stating that we had been torpedoed but were able to proceed slowly.
17/0242 USS PLUNKETT: Received report that USS KEARNY was torpedoed, went to her assistance.
17/0349 HMCS PICTOU: Chased U-boat on surface for 45 minutes, evaded a torpedo that passed 15 feet on port and dropped two patterns of 10 depth charges each squarely over her after she crash dived, but at 0420 the Asdic broke down.

Assessment: The destroyer attacked can clearly be identified as USS KEARNY as the time and position (on the port side of the convoy) correspond and the target description of U-568 fits. Furthermore she was the only vessel attacked with more than two torpedoes that night. The only inconsistency is the claim of U-568 that the vessel broke in two and sank, while in fact the destroyer was only damaged by the hit and even managed to reach Iceland under her own power. The action described by HMCS PICTOU fits perfectly the report of U-568, so she was the corvette missed by this U-boat.

Claim: U-553 tried to overtake the convoy on its starboard side for one hour after reloading the torpedo tubes, but this side was illuminated by star shells after the attack of U-432 so U-553 tried to change to the other side for an attack by crossing ahead of the convoy. There the U-boat encountered a big destroyer, identified as Tribal class and fired a spread with its last two torpedoes at 05.38 hours. One of the torpedoes became a surface runner and alerted the destroyer which turned around and chased the U-boat away from the convoy for 15 minutes.

Assessment: It seems that this attack was not noticed or not reported by the destroyer under attack. Judging from the target description and the position ahead of the convoy, the attack was probably directed against HMS HIGHLANDER which had taken station on the starboard bow of the convoy and HMS BROADWATER on the port bow after joining. USS LIVERMORE had moved to the starboard beam and USS PLUNKETT had left her station ahead of the convoy to search for the torpedoed USS KEARNY on the port side of the convoy.

The attack of U-553 between 17/0000 and 0007

Claim: At 23.30 hours on 16 October, U-553 passed a destroyer ahead of the convoy at a distance of only 150 meters and then found herself between the escorts on the port side and the port wing of the convoy. The U-boat then fired three carefully aimed single torpedoes at three different tankers, but nothing happened – apparently the torpedoes ran too deep and passed underneath the vessels, so a fourth torpedo was set to run at a depth of 2 meters and fired at a fourth tanker which was seen to explode in a ball of fire after being hit amidships. U-553 could not observe longer because a destroyer, identified as Tribal class, headed towards them and she crash dived. The U-boat was shaken by three depth charges and passed underneath the convoy, surfacing on its starboard side after 20 minutes.

Observations by other U-boats around that time:
17/0015 U-558: Sighted a column of fire, turned towards it.

Observations by Allied vessels around that time (in GMT):

16/2200 SILVERELM in station #83: Observed U-boat astern after torpedoing a tanker, was diving fast, did not open fire.
16/2200 RYM in station #85: An explosion occurred astern of the 8th column.
16/2205 HMCS BADDECK: Convoy attacked. […] Fired star shells NNE and SSE.
16/2210 USS KEARNY: Ship of convoy bearing about 080° relative struck by torpedo.
16/2212 HMCS COLUMBIA: When ahead of the 8th column, a ship was observed to be hit in the rear of the convoy in about the 7th column.
16/2213 USS PLUNKETT: Sighted red flare on starboard quarter in 56°59N/25°04,5W and fired star shells.
16/2215 W.C. TEAGLE in station #103: There was a loud explosion and the third officer reported a ship on fire well astern on the port side of the convoy.
16/2220 HMS HIGHLANDER: A red glow followed by star shell was sighted bearing 240° and course was altered towards.
16/2222 USS KEARNY: Dropped one depth charge.

Assessment: The attacks of U-553 were carried out from the port side, probably aimed at the two tankers in the 3rd column and apparently missed because the speed of the convoy was underestimated. Only the last torpedo was seen to hit, which is confirmed by the observations of several vessels of the convoy. The U-boat then entered the convoy from behind because a destroyer, most likely USS KEARNY, approached and was seen to dive by SILVERELM in station #83. However, the identity of the ship hit in this attack remained unclear, the Admiralty assumed that it was EVROS in station #64 but no details were known to them because she was lost with all hands.

The attack of U-558 between 17/0128 and 0214

Claim: At 01.15 hours on 17 October, U-558 spotted one tanker and two freighters that apparently lagged a bit behind the rest of the convoy and began to overtake them. At 01.28 hours, a torpedo was fired that missed, but was heard to detonate after 4 minutes 47 second and it was assumed that another ship in the convoy had been hit. A second torpedo then hit the tanker which was seen to catch fire and sink by the stern within 4 minutes. One of the freighters apparently stopped to pick up survivors and was then attacked and sunk with a torpedo from the stern tube. The second freighter then tried to reach the convoy again, but at 02.14 hours U-558 torpedoed it at close range.

Observations by other U-boats around that time:

17/0130 U-432: Torpedo detonations on a tanker, column of smoke is visible for a long time.
17/0210 U-432: A straggler behind the convoy is torpedoed by another boat shortly before I can carry out my own attack on it.

Observations by Allied vessels around that time (in GMT):

16/2300 RYM in station #85: Another explosion occurred ahead in 10th column, this was W.C. TEAGLE. Shortly afterwards sighted lights of survivors and we turned to pick them up being the rear ship. ERVIKEN also headed for survivors and RYM had to alter course to avoid collision. Shortly afterwards ERVIKEN was torpedoed, so we left at full speed to reach convoy again but were torpedoed at 17/0010.
16/2320 W.C. TEAGLE in station #103: There was a very mild explosion and the ship gave a violent shudder and caught fire on the after part of main deck – it is assumed the torpedo struck just forward of engine room. Tanker settled on even keel and suddenly plunged right down.
16/2320 HMCS COLUMBIA: When about ahead of the 3rd column another ship was observed to be hit towards the rear of about the 8th column.
16/2329 HMS HIGHLANDER: When about a mile on the port bow of the leading port wing ship, a ship was torpedoed in what appeared to be a position some way back in the 2nd or 3rd column.
16/2330 USS PLUNKETT: Ship torpedoed on the starboard quarter, flames reaching perhaps 300 feet, followed by a heavy black cloud of smoke in 56°59N/24°42.5W.
16/2331 USS KEARNY: Ship bearing about 065° relative struck by torpedo and burned instantaneously. Swung the ship in a circle and carried out depth charge barrage in accordance with convoy doctrine.
16/2332 USS PLUNKETT: Second ship torpedoed in same location and exploded with a heavy dull audible detonation.
16/2332 USS LIVERMORE: Sighted heavy flame from explosion.
16/2333 USS PLUNKETT: Fired two star shells to port and dropped one Mark VII depth charge.

Assessment: The description of the sinking of W.C. TEAGLE in station #103 fits the attack on the tanker at 17/0131 and the subsequent events confirms that U-558 was responsible for the sinking of ERVIKEN and RYM. What is unclear is the possible hit reported after the first torpedo missed the intended target, but the detonation heard after a running time of almost 5 minutes could have been a misinterpretation of the single depth charge dropped by USS PLUNKETT at that time.

The attack of U-432 between 17/0342 and 0448

Claim: U-432 overtook the convoy on the starboard side and entered the columns on the surface from ahead in the middle of the convoy. At 03.42 hours, a first bow torpedo was fired at the leading ship in the column following the closest column to the south, followed by a spread of two bow torpedoes on the second ship of the closest column to the south and the stern torpedo at the third and fourth ship of a column to the north. The first was seen to hit a ship after 2 minutes 30 seconds, which sank by the stern. The spread missed the intended target, but a detonation was observed after 2 minutes 55 seconds and assumed that a ship beyond had been hit. The stern torpedo hit a ship after 1 minute 20 seconds, which broke in two and sank immediately. The U-boat then spotted a tanker in one of the columns to the north, turned around and fired the last bow torpedo and hit it after 41 seconds. The tanker stopped but remained afloat, so U-432 stayed nearby and reloaded one bow torpedo tube while still on the surface. At 04.48 hours, the U-boat fired a coup de grâce that hit amidships and caused the tanker to explode and sink immediately.

Observations by Allied vessels around that time (in GMT):

17/0130 HMCS COLUMBIA: A ship in about the starboard wing column was observed to be hit followed very soon after by one fairly near the front of the 3rd or 4th column and immediately by one in the rear of about the seventh column.
17/0140 BOLD VENTURE in station #92: Torpedoed on starboard side aft, cargo of cotton caught fire but this was soon extinguished as the ship sank by the stern in about 10 minutes.
17/0145 HMCS BADDECK: Convoy attacked again, apparently on starboard side. Proceeded towards starboard bow and then to port bow of convoy closing in and firing star shells north and south.
17/0145 HMS HIGHLANDER: Another ship was torpedoed in what appeared to be the centre of the starboard wing column.
17/0145 SILVERELM in station #83: Sighted U-boat on port bow, in light of burning tanker. No opportunity to use gun, as sub was diving fast and surrounded by other ships.
17/0147 USS PLUNKETT: Two ships torpedoed almost simultaneously on starboard quarter, one of which exploded with a dull audible detonation in 57°00N/24°05W […] and dropped one Mark VII depth charge.
17/0158 USS LIVERMORE: Sighted huge blaze of ship bearing 005°T, distance about 6 miles.
17/0200 BARFONN in station #53: Hit by one torpedo on the starboard side in engine room, remained afloat.
17/0200 USS PLUNKETT: Fifth ship torpedoed in 57°00N/24°03W.
17/0200 USS KEARNY: Ship of convoy, bearing 070° relative, distance about 1200 yards, was struck by torpedo and burned brilliantly […] conducting embarrassing barrage with depth charges in accordance with convoy doctrine.
17/0202 USS KEARNY: Dropped one 600 lb. depth charge.
17/0256 HMCS COLUMBIA: A ship to port was seen to explode, flare up and vanish. This presumably was a tanker and thought to have been one that had fallen out of the convoy.
17/0257 HMS HIGHLANDER: A ship in the rear of the convoy was torpedoed.
17/0258 USS PLUNKETT: Ship torpedoed on port bow in 57°01N/23°47W. This ship appeared to be a tanker which exploded as if carrying aviation fuel, clearly outlining dull red hull of ship as flames enveloped superstructure and lit up entire sector.
17/0300 BARFONN: Hit by one torpedo on port side amidships, exploded and sank.
17/0300 USS GREER: Sighted explosion of tanker on starboard bow.
17/0300 HMCS BADDECK: Left port quarter and approached centre astern of convoy and proceeded in general direction of 270° in search of survivors. Saw explosions in neighborhood of convoy. Saw several lights to west and southwest apparently from boats.
17/0305 USS LIVERMORE: A ship on port beam exploded violently.

Assessment: U-432 very likely entered convoy from ahead between the 6th and 7th column and fired the first three torpedoes to the south at two ships in the 9th and 8th column and the stern torpedo at two ships to the north in the 6th column. The U-boat then turned around and headed for the tanker in station #53 to hit it with the fourth bow torpedo, remained close and sank her afterwards with a coup de grâce.


Sketch: The approximate movements and attacks of U-432 within convoy SC-48. Note: There were probably some gaps in the columns of the convoy, especially in the 7th column due to earlier losses or stragglers.

BOLD VENTURE had originally been in station #94, but moved to #92 after other ships of this column became stragglers – the time of the hit and her position within the convoy confirms that she was hit by the first torpedo of U-432. The only discrepancy is that the hit was reported as coming from the starboard side, which is understandable because this was now the exposed side after the earlier losses of the 10th column while in fact the torpedo came from within the convoy and hit her port side. The detonation observed about 3 minutes after the spread of two torpedoes was fired is unlikely to have been a hit on another ship of the convoy because the running time is too great. It is possible that they mistook the single depth charge dropped by USS PLUNKETT at that time for a torpedo detonation. The stern torpedo was seen to hit and sink a ship, which is not identified in any Allied report but was observed by USS PLUNKETT and HMCS COLUMBIA. Judging from its position in the convoy and the description of the sinking, it is likely that this was EVROS in station #64 - her heavy load of iron ore would have caused her to sink so suddenly. The subsequent attacks on the tanker were clearly directed against BARFONN in station #53.

The loss of HMS GLADIOLUS

The above analysis of all U-boat attacks during the night in question shows that only three attacks could have been responsible for the loss of HMS GLADIOLUS, as visible in the following table:

Time U-boat Grid Target Weapon Confirmed
17/0000U-553 AL 1962 Tanker, 6000 T (1) Missed
17/0004 U-553 AL 1962 Tanker, 6000 T (1) Missed
17/0005 U-553 AL 1922 Tanker, 6000 T (1) Missed
17/0007 U-553 AL 1922 Tanker, 6000 T (1) Hit ?
17/0128 U-558 AL 1966 Tanker, 7000 T (1) Missed, claimed hit after 4 min. 47 sec.
17/0131 U-558 AL 1966 Tanker, 7000 T (1) Sank W.C. TEAGLE
17/0149 U-558 AL 1966 Steamer, 6000 T (1) Sank ERVIKEN
17/0214 U-558 AL 1966 Steamer, 4000 T (1) Sank RYM
17/0342 U-432 AL 0143 Steamer, 6000 T (1) Sank BOLD VENTURE
17/0343 U-432 AL 0143 Steamer, 5000 T (2) Missed, claimed hit after 2 min. 55 sec.
17/0346 U-432 AL 0143 Steamer, 7000 T (1) Sank EVROS
17/0400 U-432 AL 0143 Tanker, 12000 T (1) Damaged BARFONN
17/0415U-568 AL 0146 Destroyer, 1400 T (4) Damaged USS KEARNY
17/0448 U-432 AL 0143 Tanker, 12000 Tf (1) Sank BARFONN
17/0538 U-553 AL 0143 Destroyer, Tribal T (2) Missed HMS HIGHLANDER
17/0602 U-568 AL 0155 Corvette T (1) Missed HMCS PICTOU

Weapon: T = Torpedo, (n) = number of torpedoes fired, Tf = Torpedo (Coup de Grâce)

The attacks at 17/0128 and 17/0343 both missed the intended targets and were claimed as hits on ships beyond when a detonation was heard, but in both cases a single depth charge was dropped by USS PLUNKETT at the times the detonations were heard, so they were probably mistaken as torpedo hits. There are also no observations reported by any vessel that would indicate that these attacks were successful.

Compared with the other attacks in question the attack at 17/0007 undoubtedly was successful, as this is confirmed by the observations of other U-boats and Allied ships – the result of the attack was described as hit on a tanker due to the column of fire seen. But no tanker was hit at that time and that it was EVROS as the Admiralty assumed is unlikely, because she carried no flammable cargo and her loss fits the description of the attack at 17/0346 very well.

The ship hit was in the after part of the port side of the convoy or astern of it as observed by the ships in the starboard wing of the convoy. HMS GLADIOLUS was on station in this area, apparently sent her last radio message at 17/0000 and did not answer anymore when asked by HMCS WETASKIWIN for identification. She must have been the ship hit by the torpedo fired at 17/0007. Like the three earlier attacks of U-553, the torpedo probably missed the intended target due to the underestimation of the speed of the convoy and the corvette was hit by chance astern of the convoy – the column of flames observed could have been the explosion of her magazine, which would also explain her sudden disappearance.

Our reassessment for “Axis Submarine Successes”:

17/0007 U-553 AL 1922 -T 6000+ T SC-48 16/2200 br PE Gladiolus 925+
17/0128 U-558 AL 1966 -T 7000=? T SC-48
17/0131 U-558 AL 1966 -T 7000+ T SC-48 16/2320 br –DT W.C. Teagle 9552+
17/0149 U-558 AL 1966 -D 6000+ T SC-48 16/2345 nw –D Erviken 6595+
17/0214 U-558 AL 1966 -D 4000+ T SC-48 17/0010 nw –D Rym 1369+
17/0342 U-432 AL 0143 -D 6000+ T SC-48 17/0140 pa –D Bold Venture 3222+
17/0343 U-432 AL 0143 -D 5000=? T SC-48
17/0346 U-432 AL 0143 -D 7000+ T SC-48 17/0147 gr –D Evros 5283+
17/0400 U-432 AL 0143 -T 12000+ TTf SC-48 17/0200 nw –MT Barfonn 9739+
17/0415 U-568 AL 0146 DD 1400+ T SC-48 17/0210 am DD Kearny 1630=

Note: This analysis was sent to Dr. Jürgen Rohwer for review and he confirmed our findings.

Many thanks to Thomas Weis, Jerry Mason, Ken Dunn and Roger Griffiths for their invaluable assistance.


This article was published on 23 May 2010.

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