Written by G H Bennett (Associate Professor, Plymouth University)

Key battle ground areas where the night actions of 27-28 April 1944 took place. The relevant squares are designated from the German Naval Grid system (Gradnetzmeldeverfahren)

Introduction

Exercise Tiger, a rehearsal for the landings on Utah Beach on 6 June 1944, is dominated in public memory on both sides of the Atlantic by the attack in Lyme Bay which took place on the T4 Convoy of 8 Tank Landing Ships (LSTs) between 0200 and 0230 on the 28 April. LSTs 507 and 531 were sunk, and LST 289 sustained heavy damage, but was able to reach the safety of Dartmouth.[1]

The loss of around 639 to 749 US Navy and Army personnel (estimates vary), the sinking of two LSTs, and serious damage to a third, was inflicted by 9 Schnellboote (S-Boats, or E-Boats in British parlance) of the 5th and 9th S-Boat Flotillas based at Cherbourg. An initial security clampdown, in which news was not released, and survivors were sworn to secrecy, was ended with publication following D-Day of a brief outline of the events of that night. The losses on Exercise Tiger received little public attention at the time and, in the midst of a brutal war, the event was effectively buried in so many other tragic days and long casualty lists. When the story re-emerged in the 1980s, thanks in large part to the efforts of amateur historian Ken Small, it became the focus of considerable speculation in book and documentary form.[2]

That has been a significant problem so far as the understanding and memorialisation of Exercise Tiger has gone. Claims of multiple overlapping conspiracies have surrounded Exercise Tiger in a spider’s web of claim and counter-claim. Genuine questions and issues of significance have been obscured in a welter of ‘revelation’ as Exercise Tiger became something of a publishing and television phenomenon.[3]

Not all of those ‘revelations’ were ‘appreciated’ by Exercise Tiger veterans, and by the families of those who had been killed in action in the early hours of 28 April 1944. This piece is an attempt to cut through some of the “fog” that has come to surround Exercise Tiger by establishing a detailed dataset in the form of a timeline from American, British and German primary sources covering the events in Lyme Bay (27-28 April 1944) that other researchers can utilise.

It is offered here open access, rather than in a paper in some remote academic journal, to ensure the widest possible access, and in a way which will allow the reader/historian to draw their own conclusions about the events of that night. The data set focusses only on the events around the T4 Convoy, with a leading commentary broken down into notional phases of the battle. The analysis will show that the events of that night were far larger, and involved significantly greater forces on the Allied side, than has previously been recognised.

Instead of there being the action against just the T4 convoy there were actions against three separate groups of Allied landing vessels with a running fight spread over several hours. Actions against landing vessels were interspersed with engagements with destroyers, with the battle extending across the English Channel with attempts being made to cut off the retreating S-Boats from their base at Cherbourg by Allied sea and air units. The timescale, and the geography of the battle space, are critical to understanding it, as in many accounts of Exercise Tiger events happening at different times, and in different locations, are compressed together to create misleading impressions.

This piece aims to detail and disentangle them to facilitate understanding and further research. The truth is that there were many witnesses to the events of that night, spread across many miles of ocean in Lyme Bay. Some were direct participants while others could only wonder what was taking place as they saw flashes in the night sky caused by tracer fire or the explosion of starshells from destroyers.

By bringing together evidence from a variety of British, American and German sources the precise chronology of events, and the way in which the engagements unfolded, can be understood. The British record is, however, somewhat incomplete as the logs of the destroyers and other escort craft involved, were destroyed after the war in the interests of saving archival space: Unfortunate, unforgiveable but probably not a way of obscuring what took place that night.

In most cases, what emerges from this chronology is a remarkably coherent picture of events with multiple parties witnessing critical events from different perspectives. This is an important process. That night in April 1944, as the battle developed, the British and Americans did not wholly understand each other’s dispositions.

Indeed, a breakdown in communication with the Royal Navy and United States Navy using different radio frequencies, was central to the temporary loss of sea control off the Devon-Dorset coast. Warnings about approaching S-Boats, broadcast by Royal Navy units and shore stations, were simply not received by American vessels. Moreover, the British and Americans certainly had little idea of the actions and perceptions of the German Kriegsmarine about the events of that night, and after the war efforts at understanding the German version of events were perfunctory at best.

By bringing these different narratives together, enshrined in the logs of the different ships taking part, and in the after-action reports written in April-May 1944, we can better understand the events of that night and appreciate their significance. In bringing these narratives together, no attempt has been made to reconcile the information derived from the logs of American LSTs, British escort vessels, German S-Boats and other reporters so there are slight differences between different participants in the reported timing of some events.

They are, however, remarkably close (a matter of minutes) especially allowing for inevitable differences between the clocks on the bridges of one ship, as opposed to another, or a Commanding officer’s watch running a couple of minutes slow. Likewise if one observer identifies a vessel as a steamer, or an LST, or a tanker, or landing craft then this dataset does not seek to resolve what might be seen as a contradiction: A separate target to that described by another observer, even though an LST is a steamer, and a landing craft at the same time, and a burning LST, with fires driven by ammunition and the exploding gas tanks of vehicles down below, could very easily be mistaken for an oil tanker.

Just because different witnesses, especially at night, at distance and in a combat environment, describe something in different ways doesn’t preclude the possibility that it is, in fact, the same thing. Moreover, a precise plot of the course steered by any of the groups of participants in the Battle of Lyme Bay is difficult to arrive at. The logs of most of the LSTs do not allow a precise reconstruction of their course since position fixes are few, and travel times (the interaction between distance, speed, current, wind etc) between one course correction and another are not given in such detail as to allow absolute precision.

Inevitably, in any fast-moving night battle, there would, in any case, be significant question marks over even the most precise references provided by participants, especially when a convoy (as in the case of T4) might be spread over several miles, so that the difference in the position between the front of the convoy and the rear is considerable to the point where, at night, they were effectively out of visual range with each other. On the German side their preference was to provide loose references via the German Naval Grid Reference, (Gradnetzmeldeverfahren) system which broke the ocean down into a series of (roughly) 6 x 6 nautical mile squares.

For mapping purposes this chronology will utilise that same system (providing longitude and latitudes in footnotes) to facilitate understanding. The map at the start of this document highlights the most significant squares so far as the Battle of Lyme Bay is concerned, and throughout this chronology reference can usefully be made to that chart. And yes, dear reader, that map is rudimentary: A reminder that the events of April 1944 took place in an age of paper chart and pencil rather than positioning by satellite and display on screen.

UK, Atlantic and North Sea – German Naval Grid Reference Chart

By viewing the losses of the T4 convoy against the wider context of the events of that night a broader understanding emerges. Survivors reports which have puzzled and perplexed researchers for several years
suddenly make sense, as incidents which have previously been put down to ‘the fog of war’ can be fitted into a wide-ranging and confusingbattle. And it is important that we use the label ‘battle’. Some
aspects of Exercise Tiger were undoubtedly tragic but perhaps instead of emphasising the tragedy of Exercise Tiger we should see the action against the T4 convoy for what it was: The central element in what
should be better known as the Battle of Lyme Bay.

What began as a training exercise resulted in a battle lasting several hours involving multiple naval units. The dead of the T4 convoy were combat fatalities, just as much as if they had been lost on the D-Day mission for which they were training. They died in action with the enemy, and their sacrifices were no less heroic, in a battle which has been lost to history. Indeed, through revealing the bigger picture of the Battle of Lyme Bay, the full importance of the events of that night become apparent. The losses to the T4 convoy were serious: Serious in strategic terms as well as human terms. However, a far bigger disaster that night, with potentially far-reaching consequences, was only narrowly avoided.

Phase 1: Advance to Contact 27 April

During the night of 27-28 April. The seas off the South Coast of South West Britain were exceptionally busy. Exercise Tiger, a rehearsal for the Force U landings on Utah Beach, was in full swing. The number of vessels involved in the rehearsal was considerable.[4] The destination for most of these specialised landing craft was Slapton Sands and the surrounding area; part of the South Devon coast taken over by the US Military in late 1943 to serve as a practice landing area.

In addition to the invasion craft, other groups of ships were at sea in the vicinity for other purposes. For example, Convoy WP.513 (20 Merchant Ships on one of the regular coastal convoy routes from West Wales to Portsmouth), had departed Milford Haven on 26 April 1944 and was scheduled to arrive at its destination on 28 April.[5]

With much of Lyme Bay in use for training, convoys moving across the South West coast of the UK had to travel further out into the English Channel, bringing them closer to the coast of France and the torpedo and cannon equipped S-Boats of the German Kriegsmarine.

Phase 1 Chronology

2200 5th (S100/143, S140/142, S136/138) and 9th S-Boat Flotillas (S130/145/150) leave Cherbourg, following reports that a WP convoy is in vicinity of Portland. This is important, and there are some differences in interpretation as to why the German initiated this operation. Doenitz after the war said that ‘We did not suspect anything in particular, but naturally everyone was alert for a possible invasion, and we were attempting to slip closer to the English ports under the cover of darkness and thereby extend the range of our reconnaissance’.[6]

The Record of S-Boat Operations, translated by the Admiralty from contemporary German records is, however, very specific stating that the 5th and 9th Flotillas left Cherbourg ‘to attack WP convoy 10 miles west of Portland’. [7]

With the German Naval Intelligence Service (B-Dienst) routinely being able to read many of the signals sent in the Admiralty’s ‘Small Ships Basic Code’ cypher (with a delay in decoding of several hours)[8] this, together with traffic analysis and on-going efforts at signals direction finding, may have been the intelligence source which prompted the operation. After leaving Cherbourg the S-Boats proceed to the West to elude close blockading forces. At the Channel Islands they turn North and head towards Lyme Bay. 2305 LST382 ‘Beached on Slapton Sands, England’.[9]

She is one of a number of LST’s that either beach or anchor immediately offshore.[10]

LST Flotilla 10, for example, is moored offshore during the night of 27-28 April and during the night they observe tracer fires and flares, estimated at 10 miles, during the next few hours.[11]

A considerable number of vessels are at sea or moored in the vicinity of Lyme Bay. At the end of 27
April:‘Force U after landing division 4 of VII Corps in assault during 27th April at nightfall had under protection in transport area Slapton Beach 1 APA, 21 LSTs, 28 LCIs, 65 LCTs, 14 miscellaneous and 92 small landing craft or total of 221 awaiting unloading and sailing empty at daylight’.[12]

2316 S140/142 S-Boats as they approach Lyme Bay break up into groups BF2636 bottom right of the box. 2317 BF2626 Flotillas break down into pairs for sweep northwards following radio message that there is a fix by radio at BF2398. 2352 T4 Convoy LST58 notes white flare observed.[13]

2355 Portland Command ‘4 groups were plotted from Portland Bill about 12 miles from the
convoy route steering north into Lyme Bay at 36 knots’.[14]

Phase 2: Penetrating the Destroyer Screen 28 April 0000 to 0059
Exercise Tiger was defended by a series of covering patrols. These
included on the night of 27-28 April:
Force 27 – HM Destroyers ONSLOW and OBEDIENT
Force 28 – HM Destroyers OFFA (above) and ORWELL
Force 113 – MGB 329 and 322
Force 114 MTB 430, 414, 434
Force 115 MTB 239, 92, 91 and 90 set to patrol off Ile de Bas from 2300 to catch any S-Boat departing Cherbourg. At around midnight the S-Boats which had advanced Northwards before splitting into 4 groups (S136/138, S100/143, S140/142 and S130/145/150) (Von Mirbach 9th S-Boat Flotilla Leader in S150) tried to penetrate the screen of destroyers designed to protect the invasion exercise.

S136/138 had a particularly strange encounter in which torpedoes fired at two destroyers resulted in a large explosion seemingly without striking anything. On both the German and British vessels the explosion was witnessed with debris falling onto the decks of the British destroyers. This must have resulted from premature detonation of the torpedoes, which were fitted with TZ3 magnetic firing pistols. They may have detonated each other, or struck a mine or other obstruction that caused their detonation.

As a result of the engagement, S136/138 which had fired off all their torpedoes, decided to return home in the early parts of Phase 2 of the action. Once the destroyer screen has been
negotiated, the remaining 7 S-Boats were lost in the radar clutter of the many vessels at sea as part of Exercise Tiger.

Phase 2 Chronology

0000 S136/138 BF2393[15]

Two stack destroyer off port bow, also another destroyer to the northwest visible. Proceeding slowly at 7 knots.
0003 S100/143 Notes that S138 is reporting to S136 that there is a vessel to port. A few minutes later a large detonation with two columns of water. Flares are seen. Attempts to contact S136/138 fail.
0003 S130/145/150 See brief brilliant light at 70 degrees.
0004 ONSLOW/OBEDIENT Note ‘in position 50°18’02″N, 002°35’05″W. Course 223 degrees, 16 knots, Radar contact 155 degrees 3400 yards’.[16]

00041⁄2 2 E-Boats sighted on HMS OBEDIENT.[17]

0005 ONSLOW/OBEDIENT ‘Very loud and fiery shallow explosion observed close of OBEDIENT’s port side’.[18]

0006 ONSLOW/OBEDIENT Opened fire with starshell.[19]

0007 Portsmouth Command C-in-C Portsmouth passed out to all ships on port wave that radar contacts had been obtained in the vicinity of Portland – course North.[20]

0007 S136/138 S138 double shot TZ3 (magnetic pistol torpedo) at right rear destroyer (10 knots, range 2000m) 0008 S136/138 S136 single shot TZ3 (magnetic pistol torpedo) at front destroyer (12 knots, range 2000m).
0009 S136/138 Detonation felt strongly in S136. S138 convinced that they have obtained a torpedo hit at the second stack (run time 100 seconds). Admiralty War Diary later records: ‘ONSLOW reports that during approach of E-Boats in Lyme Bay night of 27-28 April there was sudden explosion in vicinity of ONSLOW and OBEDIENT as of depth charge or mine, and fragments fell on board.’[21]

The fragments were later described as pieces of container which landed abreast the funnel on OBEDIENT on the port side.[22]

On further reflection the Commanding Officer of HMS ONSLOW considered that this was debris
from a torpedo which had exploded in the wake of his ship.[23]

0010 S136/138 Leaving area of engagement at 34-36 knots.

0011 HMS ONSLOW patrolling off Portland Bill encounters E-Boat on Northerly course. After a few minutes the boat retired to the South.[24]

0020 S136/138 Destroyers moving slowly. S136 fires two FAT torpedoes at destroyers at a
range of 1800m.

0020 Admiralty War Diary records ‘3 groups of E-boats were plotted between 10-20 miles W.S.W. of Portland Bill, steering northwest, and apparently searching to the northwestward’. These groups were also plotted at Portland, but owning to the disposition of forces dispersing from Exercise Tiger not being known, the Portland Plot was rather confused’.[25]

0020 ONSLOW/OBEDIENT Lost contact with the enemy.[26]

0020 T4 Convoy LST289 Logs flares, several miles away at 090 true.[27]

0020 T4 Convoy LST58 Logs flares, at 030 relative about 7 miles away.[28]

0021 T4 Convoy LST58 Convoy course changed to 145 True.[29]

0022 S136/138 S138 fires two torpedoes. Torpedoes miss and destroyer gives chase. S-Boats retreat at 20 knots with harassing fire from the destroyer.

0035 S136/138 Pair stop as destroyer out of sight. S138 attempts to contact S136 by coded message to warn of destroyers in BF2393. Message is not received, but boat-to-boat conferral takes place after which they attempt to move back to the northwest at 15 knots to see what has happened to the destroyer and to capture any floating sailors.
0039 Portsmouth Command Report from HMS ONSLOW passed to Commander Force U
0041 S100/143 receives message from S138 that there are two destroyers in BF2393
0050 S136/138 FDS (Fuehrer der Schnellboote, Rufolf Petersen), reports 2 destroyers approaching from the East. S138 reports back that a destroyer is sinking [presumably relating to the one they thought had already been torpedoed].
0052 S100/143 FdS sends out message reporting destroyers moving in from the East.
0055 S136/138 Pass over site of suspected destroyer sinking – nothing found.
0055 S140/142 Shadow at 70 degrees
0058 S100/143 Hear S138 reporting Destroyer sinking.

Phase 3: Actions Against Shallow Draught Vessels in BF2364

[30] 28 April 0059 to 0059 Convoy Route for TM.5 contained in Exercise Tiger Operational Order via Steve Mutton, NARA

Having penetrated the destroyer screen S140/142 encountered an unknown number of small landing craft. There are indications that these may have belonged to convoy TM5 consisting of Landing Barges (LBVs32-40/47/54-61, LBOs42-44/46/49-51, LBEs4/45/48/53, LBW53 sailing from Teignmouth and 18 LCMs [Landing Craft Mechanised] sailing from Exmouth).[31]

Departure time from Exmouth 2015 on 27 April. ML214 was acting as escort and lead. The Convoy was timed to arrive at Slapton Sands at 0800 on 28 April.[32]

The shallow draft of the vessels caused consternation amongst the crews of S140 and S142 as they fired multiple torpedoes at the landing craft without effect as a result of the shallow draft of the landing barges.

Phase 3 Chronology

0059 S140/142 detect 3 small steamers 6-800 tons running SE. Signal made to other S-Boats convoy 7 nautical miles North of point Z. S140 double shot depth 3m range 1800m – missed. Adjusted, reduced depth to 2m range 1400m firing single shots.[33]

0100 S136/138 Stop – presumably for conferral.[34]

0106 S136/138 decide to return home as they are out of torpedoes.[35]

0113h S140/142 S142 Double shot, missed. Single shots – missed.[36]

0114h S100/143 Hear recon reports from S140 reporting a convoy 7 nautical miles north
of point Z. S100/143 head for point Z. 0114 S130/145/150 Recon reports from S140 indicate convoy 7 nautical miles. Heads towards that point on Z course 70 degrees at 34 knots.

0126 S140/142 Stopped in square BF2364 for conferral. They presume missing because of the variable speed of the landing craft, but also consider that they might be shooting under them. Two torpedo detonations observed on land.

0130 S140/142 S140 Sends report of another convoy. Proceeds to attack with gunfire to highlight the position of the convoy to other S-Boats. Senior officer on LST289 later suggests that the fire was directed at LST507 some 600 yards from him. He further suggests that it was 40mm fire from a position almost due west at a distance of 2500 to 4000 yards.[37]

No hits were recorded on LST289 with around 300 rounds fired from behind LST289.
0130 HMS SALADIN on patrol between the Mewstone and Dart Buoy receives message from HMS ONSLOW reporting E-Boats. Proceeds towards Lyme Bay at 0137.[38]

0134 9th Flotilla S-Boats reduce speed to 24 knots. Machine gun fire at 40 degrees (red
tracer).

Phase 4: Developing the Attack Against the T4 Convoy 28 April 0135 to 0230 in BF2365

Report of Action Between LST Convoy and Enemy E-Boats, Night 4/27-28/1944 in the English Channel, COMLST GR32, A1061, RG38, NARA.

Following the unsuccessful engagement with shallow draft landing craft S140/142 detected the far larger and deeper draft LSTs. Convoy T4 (under the Command of Commander B.J. Skahill) consisted of LSTs
515,496, 511, 531, 58, 499, 289 and 507, and carried US Army units designated to land on Utah Beach. LST’s 515, 496, 511, 531 and 58 had departed Plymouth at 0945 on 28 April.[39] At 1100 HMS AZALEA joined as escort and lead ship. At 1930 the convoy was joined by LSTs 499, 289 and 507 departing Brixham and heading towards Lyme Bay. The convoy was scheduled to land at Slapton Sands at 0730 on 28 April.[40]

Some ships of the Convoy witnessed the attack on the shallow draft vessels in their vicinity coming to General Quarters in response. However, an attack on the vessels of the T4 Convoy did not immediately develop and the ships of the convoy secured from General Quarters before S140/142 began their gun run against the LSTs to bring other S-Boats to launch their torpedoes against the Convoy.

Phase 4 Chronology

0130 T4 Convoy LST531 General Quarters sounded as a result of gunfire and flares being seen.[41]

0133 T4 Convoy LST58 General Quarters sounded as a result of gunfire and shells off her stern.[42]

0133 T4 Convoy LST58 General Quarters sounded as a result of fire directed at convoy from 165 Relative. Fire passes over LST58 and hits water 400-600 yards away.

0135 S140/142 Steering to 260 degrees at 36 knots ceased firing.

0135 S100/143 Observe 4cm fire to the North. S140 reports convoy on a southerly course and that the boat is in BF2365. S100/143 head that way at 24 knots.

0135 T4 Convoy LST515 Gunfire heard, believed LST511 firing to port.[43]

0138 S140/142 S140 sends message that his position is BF2365.

0143 S100/143 Note convoy in view to the North East. Course is southerly.

0144 LST Group 30 LST133 observe starshell and tracer fire.[44]

0145 S140/142 S140 sends message announcing that he is returning to port.

0147 S130/145/150 Observe vessel at 90 degrees. Torpedo attack prepared. Course 65 degrees. Convoy observed on a southerly course.

0148 LST Group 30 LST157 observe starshell and tracer fire.[45]

0150 T4 Convoy LST531 General Quarters sounded as a result of gunfire and flares being seen.[46]

0153 T4 Convoy LST515 Secure from General Quarters.[47]

0155 S130/145/150 Short code message sent to report convoy in BF2365 centre, southerly course. Torpedo attack behind target with S150 and S130 working together. S145 attacking ‘smaller units bringing up rear.’

0200 S130/145/150 Double shot. Hit 2 minutes and 27 seconds. Steamer goes up in flames. It is assumed it is a tanker. No defensive measures taken by convoy as boats prepare 2nd pass.

0200 S140/142 S140 sends message of a sighting of three steamers.

0202 T4 Convoy LST58 sees LST507[48] torpedoed.[49]

0203 S100/143 tanker torpedoed by another boat is burning covering the bay with smoke.

0203 T4 Convoy LST531 Underwater explosion detected. Officer of the Deck asks Quartermaster of the Watch to log the event.[50]

0203 T4 Convoy LST289 Witnesses torpedo hit on LST507.[51]

0204 T4 Convoy LST531 Ship on fire observed by Ensigns Harlander and Cantrell. There is
uncertainty as to the identity of the vessel.[52]

0204 T4 Convoy LST515 LST507 hit by torpedo.[53]

0205 S100/143 Manoeuvred into firing position. Fired at steamer 2-3,000 tons. Took aim at next steamer.

0206 T4 Convoy LST58 explosion and burning ship reported. From the radar plot it is
assumed to be LST507.[54]

0210 T4 Convoy HMS AZALEA observes tracer fire and comes to action stations.[55]

Convoy at this stage is about three miles long.[56]

0214 S100/143 Fired double shot at 1500m shots missed.

0215 LST Group 30 LST134 observes red tracers astern of convoy. LST51 logged white lights and tracer (bearing 250 at 0220).[57]

0215 T4 Convoy HMS AZALEA observes LST being torpedoed and catching fire. ‘Within a
minute or two’ a second LST is torpedoed.[58]

0216 S100/143 S143 fired two single shots at 1500 steamer, hit after 76 seconds. Steamer sinks in flames. Situation confused with smoke. Two boats of 9th flotilla sited.

0217 S130/145/150 Double shot at steamer by S150. Both hit home after 56 seconds. Steamer bursts into flame. S145 hits landing craft in stern. It is estimated that it is 200 tons. Sinking not observed and Von Mirbach, Commanding 9th S-Boat Flotilla, considers it unlikely that it foundered.

0217 T4 Convoy LST58 LST531 engulfed by explosion.[59]

0218 T4 Convoy LST531 Struck by torpedo and then another about a minute later.[60]

0218 T4 Convoy LST515 observes by radar two S-Boats cut through the columns of the convoy from starboard to port.

0219 T4 Convoy LST289 observes LST hit by torpedo.[61]

0219 S130/145/150 After watching the carnage for 2 minutes the S-Boats retreat with random defensive fire sent their way.

0220 T4 Convoy LST515 opens fire with starboard guns on radar bearing 351 true.[62]

86 rounds of 40mm ammunition expended, vessel taking evasive action.

0224 T4 Convoy LST531 rolls over and the order is given to abandon ship.[63]

0225 T4 Convoy LST58 observes S-Boat to port approximately 1500 yards. Order given to open fire.[64]

0225 T4 Convoy LST515 visual contact on S-Boat opened fire.[65]

0228 T4 Convoy LST289 Gunners open up on what they believe to be an S-Boat.[66]

A torpedo hits them in the stern. Position estimated at 50 deg, 28.2 minutes North/2 deg, 49.6 mins West (260 deg off Bill of Portland at a distance of 14.5 miles).

0230 T4 Convoy LST58 Explosion heard astern of the ship.[67]

Phase 5: S-Boat Retreat to the South and Engagement with Convoy (OBSTACLE) 28 April 0230-0332

As the remaining S-Boats retreated to the South after the attack on the T4 convoy they ran into a convoy of 8 LSTs of LST Group 30 that were not part of Force U or Exercise Tiger. Some 30 minutes after the
attack on T4 Convoy this second LST Convoy (code name OBSTACLE) found itself on the line of retreat of the S-Boats heading southwards back towards Cherbourg.[68]

LST Group 30 had sailed from Falmouth on Thursday 27 April and formed a convoy. Each ship had anchored off Pendennis Point to take in tow a Rhino Ferry on the end of about 200 feet of cable. The Log of LST51 says they left Falmouth Channel at 1145, bound for Portland.[69]

They were routed well away from the Exercise Tiger practice area which meant a voyage someway south of the invasion craft circling around Lyme Bay. Acting as escort were two USN Vessels PCs 1232 and 1233.[70] Other vessels joined and left the convoy. For example, LCTs 530 and 452 left the convoy as it reached Lyme Bay.[71]

PC1262, meanwhile sailed with the convoy only as far as Plymouth. At 20.05 on 27 April the convoy was reinforced by the arrival of PC552 and PC1225.

The convoy appears to have been in two columns. By midnight of 27/28 April the convoy had been under way for about 12 hours since leaving Falmouth at speeds of 7 or 8 knots that would have put them somewhere in the vicinity of Start Point off the coast of Devon.

Towing Rhino Ferries, even in two columns the convoy was spread out over a considerable distance.

At 0059, with S-Boats known to be in Lyme Bay, a signal had been sent to the convoy to get it to reverse course. That signal was not received.[72]

As the attacks developed to the North of their position the vessels of LST Group 30 observed flares and tracer fire. By 0230 LST Group 30, in the vicinity of square BF2397[73],found itself in growing danger.

[74] Three groups of S-Boats passed through the area of the convoy, but most had expended their torpedoes. At least one of the groups of S-Boats was detected on radar and engaged by Royal Navy destroyers.

In the middle of this developing engagement, radar on one of the destroyers detected contacts which turned out to be the OBSTACLE convoy. The S-Boats were fired at, but so too (for an estimated 45 seconds) was the OBSTACLE convoy.

This mistake was later put down to ‘the [radar] operator [who] unwittingly changed targets… to the LST convoy’.[75]

While one of the S-Boats was damaged, the vessels of the OBSTACLE convoy were fortunate that a problem (the fuse key broke) had developed in the ‘A’ turret of HMS ONSLOW. As a result, the only
weapons to fire at the American vessels, until they switched on recognition lights, were 20mm Oerlikons and 0.5 Pom Pom. As the report of the Commanding Officer of HMS ONSLOW later observed ‘the situation report did not mention an LST convoy routed to seaward of our patrol lines’.[76]

No damage appears to have been done. The Germans witnessing the fusillade of fire at their own vessels and the American convoy preferred to carry on their flight to the south, rather than attempt to
engage the destroyers or the OBSTACLE convoy. In addition, with the destroyers forced to check their fire, an ideal opportunity was presented for the S-Boats to ‘escape round the rear of the convoy’.[77]

By this stage units of the Royal Navy were moving to cut off the escape routes for the S-Boats. H.M. Ships STEVENSTONE and SEYMOUR and a force of Portsmouth M.G.B.’s had been sent to a position south of the Plymouth destroyer patrols to give added depth to forces in that area.
[78] Meanwhile the Free French vessel LA COMBATTANTE and HMS STAYNER
were ordered to support Convoy WP.513.[79]

Track of OBSTACLE

Phase 5 Chronology

0230 LST Group 30. LST502 log recorded receipt of S-Boat alert. On-going observation of
starshell.[80]

0232 T4 Convoy LST515 radios Portland to advise of attack – signal immediately
acknowledged.[81]

0233 S140/142 Short code message sent that convoy is in square BF2368 course south.

0232 Heavy defensive fire apparently by destroyer at first pair of boats from 5
th flotilla.

0232 S100/143 message received from FdS saying to sail to South West on return.

0233 S140/142 Steamer off port bow. They are heading south at 36 knots.

0237 T4 Convoy LST58 Bow lookout heard torpedo passing the bow.

[82] 0240 S130/145/150 Order to report/return sent to S145 by code message. Return course plotted to go east of the destroyer group reported by S140 in BF2389.

0240 OFFA/ORWELL both reported S-Boats in their vicinity

0242 S100/143 set off to return home. FdS and S140 reporting destroyers trying to cut
off their escape.

0245 LST Group 30 LST157 hears explosions bearing 295.[83]

0250 LST Group 30 LST286 logs a radio voice message from a vessel being attacked by S-
Boats, 15 miles from Portland on a bearing of 250.[84]

0255 ONSLOW/OBEDIENT 50°08’08″N, 002°43’00″W Course 223 degrees, speed 16
knots, radar contact 210 degrees 14000 yards. It was later established that
this was the convoy of LSTs (LST Group 30) and their escort, call sign
OBSTACLE.[85]

0258 S140/142 BF2626 being pursued by two destroyers.

0300 ONSLOW/OBEDIENT hydrophone effect bearing 285 turned towards and increased speed.[86]

301 ONSLOW/OBEDIENT open fired with starshell.[87]

0303 ONSLOW/OBEDIENT visual sighting of S-Boats.[88]

03031⁄2 ONSLOW/OBEDIENT open fire with main armament.[89]

0304 S100/143 two destroyers seen shooting their flares. Considers trying to get into
position to attack as both boats have 2 torpedoes left.

0305 S130/145/150 Short code message sent reporting destroyer in BF2398. Flares and
surface fire. Four landing craft observed.[90]

0307 S136/138 Return to Cherbourg.

0308 LST Group 30 LST286, at 0308 logs sighting three fast moving small craft, lit by flares, 1 mile off the port beam on course approximately 250.[91]

03081⁄2 ONSLOW/OBEDIENT Short-range weapons open fire on targets to port and starboard.[92]

Fire continues for 45 seconds before one of the PC vessels flashes recognition lights.

0310 T4 Convoy remains of convoy heading to North East. HMS AZALEA takes up stations
zigzagging to South of them.[93]

0311 S100/143 manoeuvring against the destroyers in BF2398.

0312 S130/145/150 S145 to the west of the other boats runs into destroyer in BF2385.

0312 LST Group 30. LST157 heard the crack of several 4 or 5 inch shells passing overhead.[94]

0315 S130/145/150 observes Enemy landing craft in BF2397. Flotilla leader later writes
in his report that the destroyer appears to be firing on the LSTs.[95]

0315 HMS SALADIN arrives at the site of the sinkings.[96]

0315 LST Group 30. Senior Officer LST502 orders emergency turn to starboard. Original
course resumed at 0320.[97]

0317 S100/143 trying to establish a firing solution on destroyers. S143 hit in the stern and so they break off the attack.

0325 S100/143 9th Flotilla boats reporting enemy landing craft to the West.

0325 LST Group 30 LST133 logs a vessel (believed destroyer) 1000 yards on starboard
beam of convoy on course opposite to that of the convoy.[98]

0332 S130/145/150 Course 150 towards the Casquets. LST Group 30 continued its journey
towards Portland.

Track of OBSTALCE Convoy (proximity to BF2397) and onward journey towards Portland.

Phase 6: Disengagement 28 April 0332-0535

Following the encounter with the LSTs of LST Group 30 the S-Boats continued to run for home with aircraft sent to try and attack them before they reached Cherbourg. Despite the attacks all vessels returned home safely.

Phase 6 Chronology

0340 S130/145/150 Casquets visible on port beam. Running south of the Casquets.

0345 LST Group 30 LST157 saw a destroyer 1 mile away on starboard bow.[99]

0345 Fleet Air Arm. attacks by Albacore aircraft sent by Blackgang to intercept Tiger
attackers on 3 craft possibly MOEWE class 4 miles north Cap Levi.

Unsuccessful[100] 0432 T4 Convoy LST58 arrives Chesil Cove to find 3 other LSTs sheltering there.[101]

0435 T4 Convoy LST515 begins rescuing survivors from LST507/531.[102]

0442 FdS reports 3 destroyers in BF2398.

0445 S130/145/150 met second pair of 5th flotilla near Cap de la Hague.[103]

0453 S100/143 Attacked by aircraft in square BF3543 bomb attack. No damage.

0500 HMS ONSLOW arrives as the site of the sinkings and begins rescue work.[104]

0502 Albacore attack on 3 E-boats in the Race of Alderney. One hit on stern.[105]

0507 S140/142 Arrive Cherbourg.

0515 S130/145/150 minus S145 Enter Cherbourg.[106]

0520 T4 Convoy HMS AZALEA in contact with LST289, decides to escort to Dartmouth. HMS
SALADIN at site of sinkings.[107]

0530 S100/143 Return Cherbourg.[108]

0535 S130/145/150 S145 returns to Cherbourg

0600 LST Flotilla 10 Receive parts of a message from escort vessel to flagship received by LST Flotilla 10 off Slapton reporting attack on T4 convoy.[109]

Phase 7: Aftermath 0600 28 April and Beyond

LST289 Casualty List contained in report of Action Between LST Convoy and Enemy E-Boats, Night 4/27-28/1944 in the English Channel, COMLST GR32, A1061, RG38, NARA.

Following the return to Cherbourg of the S-Boats the allies were left to continue rescue and recovery work, with casualties landed at Portland and Dartmouth.

Phase 7 Chronology

0600 LST Group 30 heads into Portland Habour.[110]

Arriving at the same time is LST515, escorted by HMS SALADIN, carrying wounded and survivors.[111]

With no base facilities, around 50 US Army ambulances turn up to ferry the wounded to nearby facilities. Over the next four days drifters and coastal craft recover around 320 bodies from the sea.[112]

The escort of convoy T.4. was taken over by HM Ships BRISSENDEN, PRIMROSE and DIANTHUS.[113]

0650 Slapton Sands ML304 came alongside LCH86 and put Captain Tompkins, USN, Chief of
Staff Task Force U on board (at 0855) – after which he departed towards scene of
attack.[114]

0700 T4 Convoy Ensign Harlander rescued by HMS ONSLOW. He later estimates that 142 Navy
and 354 Army personnel had been aboard. Picked up were 28 Navy (15 hospitalised) and 44
Army (10 hospitalised) personnel. From LST 531 this meant 114 Navy and 310 Army personnel were dead and missing.[115]

0908 Slapton Sands Tompkins (USN), Chief of Staff to Task Force U, on ML304 spoke to
LST289 ‘to ascertain needs’.[116] U.S. LST289 was escorted into Dartmouth by HMS AZALEA and tugs sailed from there to assist her.[117] Total fatalities estimated at 330-350[118]

1115 LST Group 30 LST157 Pilot Wren has to leave LST157 for immediate transfer to LST515 which is ‘proceeding into harbour with casualties’.[119]

1150 T4 Convoy LST515 arrives Portland to unload 45 dead, 14 litter cases, 118 walking survivors.[120]

Conclusion: The Significance of the Battle of Lyme Bay

The Strategic Picture

The sinking of 2 LST’s and severe damage to a third, with the loss of hundreds of lives was a shocking blow to Anglo-American forces in the run up to D-Day. While the Allied invasion fleet on 6 June would
number around 7,000 vessels, the LST was a vital and highly specialised component in the invasion plan. There were just over 100 of them available for D-Day, and no other vessel could do the job of an LST in
delivering substantial quantities of heavy equipment direct onto the beach, before floating free on the incoming tide to return to port and take on board the next load.

The removal of three LSTs from the Allied order of battle for 6 June was of great significance. LSTs were in demand in every theatre of operations and they could not easily be replaced. Indeed, Churchill’s correspondence for early 1944 shows his impatience and concern at the number of available LSTs.

On 16 April he commented: ‘How it is that the plans of two great empires like Britain and the United States should be so much ham-strung and limited by a hundred or two of these particular vessels will never be understood by history’.[121]

The day after the Battle of Lyme Bay Churchill could be found writing to President Roosevelt to welcome a statement by Admiral King that LSTs that were being kept in the Mediterranean for a planned
invasion of Southern France might be released for service on D-Day.[122] The losses on the T4 convoy mattered.

As is well known, in the run-up to 6 June Churchill became increasingly depressed by the thought that D-Day might result in a slaughter as great as that of the first day of the Somme offensive in 1916.

It also has to be remembered that his political career had been temporarily ended by the 1915 Gallipoli landings when amphibious landings on the coast of Turkey had gone badly wrong.

Despite the security clampdown which followed Exercise Tiger with survivors being sworn to secrecy so as not to give the Germans information, and to prevent damage to the morale of Allied forces in the run up to D-Day, the attack on the T4 convoy was a harbinger of what might come with the invasion of France, that lodged very firmly in the minds of Allied planners.

The United States Navy was particularly alarmed at the dangers posed by the S-Boat and considered a plan, fortunately abandoned, to target the S-Boat Bunker at Cherbourg in the hours before D-Day for heavy bombardment by the battleship USS NEVADA.[123]

Such an operation might have been interpreted by the Germans as warning that the invasion was imminent. Torpedo Problems and the Averting of a Bigger Disaster It is against this background that the Battle of Lyme Bay must be evaluated, as it becomes clear that the events of that evening had carried the potential for a far greater disaster.

The nine S-Boats were carrying 36 torpedoes between them as they entered Lyme Bay, but only a handful hit home that night. The expenditure of 8 torpedoes, as S136/138 engaged the destroyer screen without result was fortunate.

Indeed, whatever ignited one or more torpedoes in the vicinity of HMS ONSLOW and OBEDIENT perhaps saved one or other (or perhaps both) of them from being hit.

Circumstantial information from other parts of the actions fought that night points to the possibility that several other torpedoes fired that night similarly exploded prematurely.

Allied good fortune extended to the action launched against landing
craft by S140/142. Defeated by the shallow draft of the vessels, they appear to have expended their torpedoes before the T4 convoy was contacted.

They could only engage the T4 convoy with cannon and machine gun fire. By this stage eight torpedoes had been fired with no result.

The luck of the Allies ran out as the three S-Boats attacked the T4 convoy with such devastating losses, but in that engagement the 3 S-Boats which engaged the convoy shot off most, but perhaps not all, of their torpedoes (12 in total). A total of 2 ships sunk and a third damaged was not a great return on the number of torpedoes expended.

With additional Allied forces being vectored to the help of the T4 convoy, and to cut off the escape route of the S-Boats, German forces preferred to run South towards home rather than try to hunt down more
of the LSTs from T4, or to engage the OBSTACLE convoy which they ran into by chance. S100/143’s manoeuvrings against a destroyer in BF2398 (presumably closing on the LST Group 30 convoy immediately to the West) was disrupted by swift action and accurate gunfire, driving off the two S-Boats which still had torpedoes ready to fire.

Whatever the number of torpedoes that went home on the S-Boats that night there must have been some disappointment that even bigger and deadlier results had not been achieved.

That being said, German reactions to the results of that night were shaped the mind-set of German forces.

The imperative to escape the contact zone as quickly as possible after an engagement was absolutely typical of German S-Boat flotillas.

As Doenitz later said about the Battle of Lyme Bay under interrogation: ‘Appreciating that the enemy forces were too strong, we withdrew’.[124] German naval forces did not enjoy superiority in the English Channel and, given their inadequacy, the need to preserve a fleet-in-being necessitated a swift retreat after any engagement.

Hit and run was the standard operating procedure of the S-Boats in the English Channel from 1941 onwards. As a result, in 1944 a chance to inflict an even larger psychological and material blow to Anglo-American forces was missed.

That blow would not have stopped D-Day, but it might have forced a delay, and perhaps dictated a change in strategy (the USS NEVADA option) with the possibility of far-reaching consequences.

Communications Issues and the Loss of Sea Control So far as the approaching invasion of Europe was concerned, the most worrying aspect of Exercise Tiger involved the loss of sea control and the failure of the intelligence net/communications plan between British and American forces.

By 1944 the British had developed an information network and a defence in-depth which was slowly strangling the German S-Boat offensive in British coastal waters.

Engima derived intelligence, photo-reconnaisance of German bases, radio intercept in real time and radar (based on ships, aircraft and the land) backed by a multiple layers of patrol lines, spread across the English Channel from the French shore to that of England meant that life was increasingly difficult and dangerous for S-Boat crews.

In April 1944, however, and especially in the midst of Exercise Tiger, the number of Allied vessels at sea meant that the radar plot was simply swamped and there were far too many friendly ships at sea for their security to be safeguarded from the fast-moving German vessels.

That intelligence net appears to have been further compromised by the signals discipline of German forces. From 1942 voice VHF (Very High Frequency) and RT (radio telephony) intercepts from approaching S-Boats frequently gave warning and potentially valuable tactical information to German-speaking operators at special Royal Navy ‘Y’ shore stations. Information could then be relayed to commands and ships at sea.

In some cases, larger vessels took operators to sea to extend the range of the intercepts and to provide real-time commentaries on S-Boat activities.

During the night of 28 April no voice VHF intercepts appear to have been logged and, indeed, the behaviour of the 5th and 9th Flotillas suggests that they were operating strict silence over VHF.

In January 1943 Fuehrer der Schnellboote Petersen ordered signals silence (both VHF and RT) on the run-in to the convoy lanes and emergency use only of voice VHF in close proximity (45 miles) to the British coast.

[125] This does not initially appear to have been strictly obeyed by S-Boat flotillas but the need for radio silence was perhaps reinforced during the following year: ‘In 1944 S-Boat ‘Command believed that the destroyers in the Seine Bay were operating with foreknowledge of German movements derived from Allied exploitation of … VHF/RT traffic’.[126]

While there is no mention in the S-Boat logs of VHF radio silence being maintained during the attack on Exercise Tiger the behaviour of the S-Boat crews suggests that it was.

During the action individual S-Boats sent brief RT signals to S-Boat command but there is no evidence of voice VHF exchanges.

Once the 5th and 9th Flotillas had broken into four groups the extent of any co-operation between them was limited.

When S140 and S142 were perplexed by their inability to torpedo shallow invasion craft the two vessels appear to have closed with each other for the purposes of a shouted conversation.

When they wished to draw the attention of other S-Boats to the presence of LSTs they used an RT message, and tracer fire, rather than voice VHF signals. Circumstantial evidence does appear to point towards a policy of not using voice VHF, and only limited RT messaging, during the attack on Exercise Tiger.

A further breakdown in the intelligence net came with the failure of the Allied communications plan. The full signals traffic on that night is not available for scrutiny, but the surviving record demonstrates
that at 0130 HMS SALADIN and HMS TANATSIDE, to the West of the T4 convoy, received an S-Boat warning from HMS ONSLOW, seemingly as a result of S140 opening fire on the shallow draft landing craft to the West of the T4 convoy, which was sufficiently serious to prompt HMS SALADIN to proceed at best speed to the assistance of the LSTs. Thirty two minutes elapsed between the receipt of that signal, seemingly not heard or interpreted correctly by any vessel on the T4 convoy, and the torpedoing of LST507.[127]

As a result, most of the vessels of the T4 convoy had stood down from General Quarters (called initially after the firing which broke out at 0130) before 0200, and a vital opportunity was missed to close-up the convoy, take evasive manoeuvres and to steer towards land and away from the danger area.

Such breakdowns of communications and missed opportunities are common to most wars but, April 1944, the consequences were particularly costly.

Lessons Learned?

In the writing of history most military misfortunes are turned into valuable learning experiences, and serve as stepping stones to eventual victory. The extent to which this might be true with Exercise Tiger is
extremely limited. The full scale of the potential calamity that night was never wholly clear to both the Americans and British. The American inquiry was limited, at best, and concluded in little more than a week.[128]

Co-operation with the British was less than full, with only a limited sharing of information, and questioning of the Commanding Officer of HMS AZALEA.[129] The communications breakdown and the lack of destroyer escort for the T4 convoy were swiftly identified as the principal issues behind the successful German attack and, in the interests of Allied unity weeks before D-Day, the United States Navy
did not seek to probe too deeply, or to place blame on either its officers or those of the Royal Navy.
The British assessment took rather longer, starting in late May 1944, but it was infinitely more thorough.

The relevant file within the Admiralty case book covering Coastal Operations in 1944 reveals vigorous debate about the tactical responses which should have been made in the midst of the developing attack through to the value of close escort as opposed to covering patrols.

The Director of the Admiralty’s Tactical, Torpedo & Staff Duties Division was particularly scathing about the latter:

The system of patrol lines which looks so solid and comforting on a chart is in fact an ensnaring myth of
security yet one in which a sublime faith is invariably put.

Naval history abounds with examples of attacking forces slipping through these thin, almost skeleton, lines but scarcely an instance of patrols intercepting and completely driving off and breaking up the attackers.[130]

The report of Admiral Leatham, Commander-in-Chief Plymouth Command, included in both the American and British Reports on Exercise Tiger, also emphasised issues which would be even more magnified on D-Day including the volume of communications traffic, late completions of plans/briefings and the fact that the planning and execution of other operations and exercises was having to be handled at the same time as the planning and execution of Exercise Tiger.[131] The strategic and tactical issues raised by the attack on Exercise Tiger, could not fully be addressed in time for D-Day.

War, even planning and training for it, is always an exercise in risk management, and in the pursuit of victory risks always have to be run.

It was perhaps a sign of the maturity of Anglo-American planning to conclude after Exercise Tiger that, on D-Day, the stakes would never be higher, and that while every effort had been made to mitigate the risks, Operation Overlord was always going to represent one almighty roll of
the dice.

Footnotes

[1] I am indebted to the Hogan Family, in particular to Dennis Hogan, for his help in
unearthing the story of the Obstacle conoy.
[2] Ken Small, The Forgotten Dead, Bloomsbury, London, 1989.
[3] See for example, Richard Bass, Exercise Tiger: The D-Day Practice Landing Tragedies Uncovered, Simon & Schuster, London, 2008; Richard Bass, Exercise Tiger Casualty Cover Up Revealed, Tommies Guides, Brighton, 2017; Wendy Lawrence, Exercise Tiger: The Forgotten Sacrifice of the Silent Few, Fonthill Media, Stroud, 2013; Nigel Lewis, Exercise Tiger: The Dramatic True Story of Hidden Tragedy of World War II,
Prentice Hall Direct, New York, 1990; Nigel Lewis, “U.S. Exercise Tiger and the Overlord Cover Plan”, U.S. Military History Review 7, no.1 (April 2021): 31-50; Stephen Wynn, Disaster Before D-Day: Unravelling the Tragedy at Slapton Sands, Pen & Sword, Barnsley, 2019.
[4] Total number of vessels involved in Exercise Tiger: 29 LST, 35 LCI, 82 LCT, 31 British LCT Mk4, 62 LCM, 4 LCG, 2 LCT (R), 4 LCF, 3 LCT (A), 5 LCT (5), 3 PC Escorts, 13 ML, 4 LCC Misc. Craft, 9 RHF, 3 APA, 2 DE, USS Augusta. War Diary, COMLANCRAB, 11th PHIBFOR, 26-28 April 1944, 0906, Record Group (hereafter RG) 38, National Archives and Records Administration (hereafter NARA).
[5] Admiralty War Diary, 28 April 1944, A2180, RG38, NARA.
[6] Doenitz Interview, 20 July 1945, ETHINT-28, M1035, RG338, NARA.
[7] German E-Boat Operations and Policy 1939-1945, TNA: ADM223/28.
[8] Review of Security of Naval Codes and Cyphers 1939-1945, TNA: ADM1/27186.
[9] War Diary LST382, 27-28 April, 1944, A978, RG38, NARA.
[10] See for example War Diary LST46, 27-28 April, 1944, A940, RG38, NARA.
[11] War Diary, COM LST-FLOT10, 27-28 April 1944, A948, RG38, NARA.
[12] Admiralty War Diary, 30 April 1944, A2180, RG38, NARA. p.503.
[13] Commanding Officer LST58 to, C-in-C US Fleet, 3 May 1944, contained in Report of Action Between LST Convoy and Enemy E-Boats, Night 4/27-28/1944 in the English Channel, COMLST GR32, A1061, RG38, NARA.
[14] Admiralty War Diary, 28 April 1944, A2180, RG38, NARA.
[15] BF2393
Top Left: 50°24’00″N, 002°40’00″W
Top Right: 50°24’00″N, 002°30’00″W
Bottom Left: 50°18’00″N, 002°40’00”
Bottom Right: 50°18’00″N, 002°30’00″W
[16] HMS ONSLOW report of action, 2 May 1944, TNA ADM199/261.
[17] HMS ONSLOW report of action, 2 May 1944, TNA ADM199/261.
[18] HMS ONSLOW report of action, 2 May 1944, TNA ADM199/261.
[19] HMS ONSLOW report of action, 2 May 1944, TNA ADM199/261.
[20] Report of Proceedings – Night of 27-28 April 1944, by C-in-C Plymouth, TNA ADM199/261.
[21] Admiralty War Diary, 28 April 1944, A2180, RG38, NARA. Portland Command War Diary for 18-30 April 1944, indicates that minelaying (including acoustic) by S-Boat and Luftwaffe in and around Portland was an on-going issue. TNA: ADM199/1395. Interestingly Exercise Tiger veteran John Casner, manning a 40mm gun on LST499, later recalled seeing surface explosions during the attack on the T4 Convoy, which he put down to torpedoes exploding against an old sunken ship, or a breakwater or the coast. John Casner Interview with Laurie Bolton, April 2015, Exercise Tiger Memorial.
[22] HMS ONSLOW report of action, 2 May 1944, TNA ADM199/261.
[23] HMS ONSLOW report of action, 2 May 1944, TNA ADM199/261.
[24] Admiralty War Diary, 28 April 1944, A2180, RG38, NARA.
[25] Admiralty War Diary, 28 April 1944, A2180, RG38, NARA.
[26] HMS ONSLOW report of action, 2 May 1944, TNA ADM199/261.
[27] Report of Action and Damage to LST289, 28 April 1944, Lt. Harry Mettler (USN), COMLST GR32, A1061, RG38, NARA.

[28] Commanding Officer LST58 to, C-in-C US Fleet, 3 May 1944, contained in Report of Action Between LST Convoy and Enemy E-Boats, Night 4/27-28/1944 in the English Channel, COMLST GR32, A1061, RG38, NARA.
[29] Commanding Officer LST58 to, C-in-C US Fleet, 3 May 1944, contained in Report of Action Between LST Convoy and Enemy E-Boats, Night 4/27-28/1944 in the English Channel, COMLST GR32, A1061, RG38, NARA.
[30] BF2364
Top Left: 50°36’00″N, 003°00’00″W
Top Right: 50°36’00″N, 002°50’00″W
Bottom Left: 50°30’00″N, 003°00’00″W
Bottom Right: 50°30’00″N, 002°50’00″W
[31] The supposition that the vessels of TM.5. might have been the ones engaged by S140/142 rests on (1) The closeness in projected landing time between T.4 and TM.5 (2) The route of TM.5 which would have taken it across the path of T.4 and circumstantial evidence on the pages of www.navalhistory.net for two of the “O” class destroyers comprising the destroyer screen for the exercise. The page for HMS ORWELL states that on 27 April she went to the assistance of ‘convoy T5 going to Slapton Sands for Exercise Tiger’. https://www.naval-history.net/xGM-Chrono-10DD-47O-HMS_Orwell.htm. That for HMS OFFA records that on the same day HMS ONSLOW: ‘Diverted to carry out search for E-Boats that had attacked US amphibious craft in Convoy TM.5 on passage to Slapton Sands’. https://www.naval-history.net/xGM-Chrono-10DD-46O-HMS_Onslow.htm The pages at issue were compiled in 2003-4 by the late Lt. Cdr Geoffrey Mason (1922-2010).
[32] Appendix III to Annex Fox to Operation Order for Exercise Tiger, 18 April 1944, via Steve Mutton.

[33] See 5th S-Boat Flotilla, Kriegstagbuch and Anlagen for April 1944 and See 9th S-Boat Flotilla, Kriegstagbuch and Anlagen for April 1944; T1022, 3211 and 3150, RG242, NARA.

[34] See 5th S-Boat Flotilla, Kriegstagbuch and Anlagen for April 1944 and See 9th S-Boat Flotilla, Kriegstagbuch and Anlagen for April 1944; T1022, 3211 and 3150, RG242, NARA.

[35] See 5th S-Boat Flotilla, Kriegstagbuch and Anlagen for April 1944 and See 9th S-Boat Flotilla, Kriegstagbuch and Anlagen for April 1944; T1022, 3211 and 3150, RG242, NARA.

[36] See 5th S-Boat Flotilla, Kriegstagbuch and Anlagen for April 1944 and See 9th S-Boat Flotilla, Kriegstagbuch and Anlagen for April 1944; T1022, 3211 and 3150, RG242, NARA.
[37] Report of Action and Damage to LST289, 28 April 1944, Lt. Harry Mettler (USN), COMLST GR32, A1061, RG38, NARA.
[38] HMS SALADIN report, 29 April 1944, contained in Report of Action Between LST Convoy and Enemy E-Boats, Night 4/27-28/1944 in the English Channel, COMLST GR32, A1061, RG38, NARA.
[39] Appendix III to Annex Fox to Operation Order for Exercise Tiger, 18 April 1944, via Steve Mutton.
[40] Admiralty War Diary, 30 April 1944, A2180, RG38, NARA. p.503.
[41] Commanding Officer LST531 to Secretary of the Navy, 2 May 1944, contained in Report of Action Between LST Convoy and Enemy E-Boats, Night 4/27-28/1944 in the English Channel, COMLST GR32, A1061, RG38, NARA.
[42] Executive Officer LST58 to Commanding Officer, 3 May 1944, contained in Report of Action Between LST Convoy and Enemy E-Boats, Night 4/27-28/1944 in the English Channel, COMLST GR32, A1061, RG38, NARA.
[43] Executive Officer LST515 to Commanding Officer, contained in Report of Action Between LST Convoy and Enemy E-Boats, Night 4/27-28/1944 in the English Channel, COMLST GR32, A1061, RG38, NARA.
[44] LST Group 30 Logs, LST51, 133, 134, 157, 285, 286, 502 towing Rhino Ferries 4, 5, 7, 8, 9, 12 and 15, NARA, via Dennis Hogan.
[45] LST Group 30 Logs, LST51, 133, 134, 157, 285, 286, 502 towing Rhino Ferries 4, 5, 7, 8, 9, 12 and 15, NARA, via Dennis Hogan.
[46] Commanding Officer LST531 to Secretary of the Navy, 2 May 1944, contained in Report of Action Between LST Convoy and Enemy E-Boats, Night 4/27-28/1944 in the English Channel, COMLST GR32, A1061, RG38, NARA.
[47] Executive Office LST515 to Commanding Officer, contained in Report of Action Between LST Convoy and Enemy E-Boats, Night 4/27-28/1944 in the English Channel, COMLST GR32, A1061, RG38, NARA.
[48] LST507 wreck site: 50°27’N, 002°43’W

[49] Commanding Officer LST58 to C-in-C US Fleet, 3 May 1944, contained in Report of Action Between LST Convoy and Enemy E-Boats, Night 4/27-28/1944 in the English Channel, COMLST GR32, A1061, RG38, NARA.
[50] Commanding Officer LST531 to Secretary of the Navy, 2 May 1944, contained in Report of Action Between LST Convoy and Enemy E-Boats, Night 4/27-28/1944 in the English Channel, COMLST GR32, A1061, RG38, NARA.
[51] Report of Action and Damage to LST289, 28 April 1944, Lt. Harry Mettler (USN), COMLST GR32, A1061, RG38, NARA.
[52] Commanding Officer LST531 to Secretary of the Navy, 2 May 1944, contained in Report of Action Between LST Convoy and Enemy E-Boats, Night 4/27-28/1944 in the English Channel, COMLST GR32, A1061, RG38, NARA.
[53] LST531 wreck site: 50°28’N, 002°51’W
[54] Executive Officer LST58 to Commanding Officer, 3 May 1944, contained in Report of Action Between LST Convoy and Enemy E-Boats, Night 4/27-28/1944 in the English Channel, COMLST GR32, A1061, RG38, NARA.
[55] HMS AZALEA report, 28 April 1944, contained in Report of Action Between LST Convoy and Enemy E-Boats, Night 4/27-28/1944 in the English Channel, COMLST GR32, A1061, RG38, NARA.
[56] Transcript of Interview between CTF125 and Commanding Officer HMS AZALEA, 29 April 1944, contained in Report of Action Between LST Convoy and Enemy E-Boats, Night 4/27-28/1944 in the English Channel, COMLST GR32, A1061, RG38, NARA.
[57] LST Group 30 Logs, LST51, 133, 134, 157, 285, 286, 502 towing Rhino Ferries 4, 5, 7, 8, 9, 12 and 15, NARA, via Dennis Hogan.
[58] HMS AZALEA report, 28 April 1944, contained in Report of Action Between LST Convoy and Enemy E-Boats, Night 4/27-28/1944 in the English Channel, COMLST GR32, A1061, RG38, NARA.
[59] Executive Officer LST58 to Commanding Officer, 3 May 1944, contained in Report of Action Between LST Convoy and Enemy E-Boats, Night 4/27-28/1944 in the English Channel, COMLST GR32, A1061, RG38, NARA.
[60] Commanding Officer LST531 to Secretary of the Navy, 2 May 1944, contained in Report of Action Between LST Convoy and Enemy E-Boats, Night 4/27-28/1944 in the English Channel, COMLST GR32, A1061, RG38, NARA.
[61] Report of Action and Damage to LST289, 28 April 1944, Lt. Harry Mettler (USN), COMLST GR32, A1061, RG38, NARA.
[62] Executive Officer LST515 to Commanding Officer, contained in Report of Action Between LST Convoy and Enemy E-Boats, Night 4/27-28/1944 in the English Channel, COMLST GR32, A1061, RG38, NARA.
[63] Commanding Officer LST531 to Secretary of the Navy, 2 May 1944, A1061, RG38, NARA.
[64] Executive Officer LST58 to Commanding Officer, 3 May 1944, contained in Report of Action Between LST Convoy and Enemy E-Boats, Night 4/27-28/1944 in the English Channel, COMLST GR32, A1061, RG38, NARA.
[65] Executive Officer LST515 to Commanding Officer, contained in Report of Action Between LST Convoy and Enemy E-Boats, Night 4/27-28/1944 in the English Channel, COMLST GR32, A1061, RG38, NARA.
[66] Report of Action and Damage to LST289, 28 April 1944, Lt. Harry Mettler (USN), COMLST GR32, A1061, RG38, NARA.
[67] Executive Officer LST58 to Commanding Officer, 3 May 1944, contained in Report of Action Between LST Convoy and Enemy E-Boats, Night 4/27-28/1944 in the English Channel, COMLST GR32, A1061, RG38, NARA.
[68] Richard T. Bass, Exercise Tiger: Casualty Cover Up Revealed, Tommies Guides, Brighton, 2017. very briefly mentions the encounter between OBSTACLE and the T4 Convoy see Bass, Exercise Tiger, pp.39-40.
[69] LST Group 30 Logs, LST51, 133, 134, 157, 285, 286, 502 towing Rhino Ferries 4, 5, 7, 8, 9, 12 and 15, NARA, via Dennis Hogan. See also War Diary, USNAAB Falmouth 27 April 1944, A848, RG38, NARA.
[70] PC1232/1233 Logs, NARA via Dennis Hogan.
[71] LST Group 30 Logs, LST51, 133, 134, 157, 285, 286, 502 towing Rhino Ferries 4, 5, 7, 8, 9, 12 and 15, NARA, via Dennis Hogan.
[72] Report of Proceedings – Night of 27-28 April 1944, by C-in-C Plymouth, TNA ADM199/261.
[73] BF2397
Top Left: 50°12’00″N, 003°00’00″W
Top Right: 50°12’00″N, 002°50’00″W

Bottom Left: 50°06’00″N, 003°00’00″W
Bottom Right: 50°06’00″N, 002°50’00″W
[74] German units estimated their position on encountering the economy to be in BF2397. The course taken by the vessels of the convoy would suggest that they were to the south of this. The logs/reports of both German and American units tie together very closely in terms of the narrative of events so this appears to be down to navigational on the part of one or both parties.
[75] HMS ONSLOW report of action, 2 May 1944, TNA ADM199/261.
[76] HMS ONSLOW report of action, 2 May 1944, TNA ADM199/261.
[77] HMS ONSLOW report of action, 2 May 1944, TNA ADM199/261.
[78] Plymouth Command: War Diary, 28 April 1944, TNA: ADM 199/1393. Admiralty War Diary, 28 April 1944, A2180, RG38, NARA.
[79] Admiralty War Diary, 28 April 1944, A2180, RG38, NARA.
[80] LST Group 30 Logs, LST51, 133, 134, 157, 285, 286, 502 towing Rhino Ferries 4, 5, 7, 8, 9, 12 and 15, NARA, via Dennis Hogan.
[81] Executive Office LST515 to Commanding Officer, contained in Report of Action Between LST Convoy and Enemy E-Boats, Night 4/27-28/1944 in the English Channel, COMLST GR32, A1061, RG38, NARA.
[82] Commanding Officer LST58 to, C-in-C US Fleet, 3 May 1944, contained in Report of Action Between LST Convoy and Enemy E-Boats, Night 4/27-28/1944 in the English Channel, COMLST GR32, A1061, RG38, NARA.
[83] LST Group 30 Logs, LST51, 133, 134, 157, 285, 286, 502 towing Rhino Ferries 4, 5, 7, 8, 9, 12 and 15, NARA, via Dennis Hogan.
[84] LST Group 30 Logs, LST51, 133, 134, 157, 285, 286, 502 towing Rhino Ferries 4, 5, 7, 8, 9, 12 and 15, NARA, via Dennis Hogan.
[85] HMS ONSLOW report of action, 2 May 1944, TNA ADM199/261.
[86] HMS ONSLOW report of action, 2 May 1944, TNA ADM199/261.
[87] HMS ONSLOW report of action, 2 May 1944, TNA ADM199/261.
[88] HMS ONSLOW report of action, 2 May 1944, TNA ADM199/261.
[89] HMS ONSLOW report of action, 2 May 1944, TNA ADM199/261.

[90] See 5th S-Boat Flotilla, Kriegstagbuch and Anlagen for April 1944 and See 9th S-Boat Flotilla, Kriegstagbuch and Anlagen for April 1944; T1022, 3211 and 3150, RG242, NARA.
[91] LST Group 30 Logs, LST51, 133, 134, 157, 285, 286, 502 towing Rhino Ferries 4, 5, 7, 8, 9, 12 and 15, NARA, via Dennis Hogan.
[92] HMS ONSLOW report of action, 2 May 1944, TNA ADM199/261.
[93] HMS AZALEA report, 28 April 1944, contained in Report of Action Between LST Convoy and Enemy E-Boats, Night 4/27-28/1944 in the English Channel, COMLST GR32, A1061, RG38, NARA.
[94] LST Group 30 Logs, LST51, 133, 134, 157, 285, 286, 502 towing Rhino Ferries 4, 5, 7, 8, 9, 12 and 15, NARA, via Dennis Hogan.
[95] ‘Enemy landing boats in BF2397, course eastwards. Destroyer attacks one of the landing boats heavily, so that it appears clear to me, that we are not dealing with a landing group (unit), as the destroyer does not appear to have known about their presence in this area. I believe these landing craft are separated units of a practice group. With general course 200 degrees retreat continued. S-145 stands a bit further west and meets destroyer at 03.12 o’clock BF2385. Gets briefly attacked and reports
with short signal.’ See 5th S-Boat Flotilla, Kriegstagbuch and Anlagen for April 1944 and See 9th S-Boat Flotilla, Kriegstagbuch and Anlagen for April 1944; T1022, 3211 and 3150, RG242, NARA. It is assumed that LST Group 30 and the 9th S-Boat flotilla were in contact with each other at this point. There is one potential discrepancy. Not recorded in the S-Boat Logs, but instead recorded in the S-Boat Command’s War Diary is mention of the fact that the Group of LST’s encountered by the 9th Flotilla at this point was escorted by ‘PC.74’. This may simply be a case of correct identification of the type of vessels escorting LST Group 30, but incorrect observation of the numbers painted on the bow of one of them. German E-Boat Operations and Policy 1939-1945, TNA: ADM223/28.
[96] HMS SALADIN report, 29 April 1944, contained in Report of Action Between LST Convoy and Enemy E-Boats, Night 4/27-28/1944 in the English Channel, COMLST GR32, A1061, RG38, NARA.
[97] LST Group 30 Logs, LST51, 133, 134, 157, 285, 286, 502 towing Rhino Ferries 4, 5, 7, 8, 9, 12 and 15, NARA, via Dennis Hogan.
[98] LST Group 30 Logs, LST51, 133, 134, 157, 285, 286, 502 towing Rhino Ferries 4, 5, 7, 8, 9, 12 and 15, NARA, via Dennis Hogan.

[99] LST Group 30 Logs, LST51, 133, 134, 157, 285, 286, 502 towing Rhino Ferries 4, 5, 7, 8, 9, 12 and 15, NARA, via Dennis Hogan.
[100] Plymouth Command: War Diary, 28 April 1944, TNA: ADM 199/1393.
[101] Executive Officer LST58 to Commanding Officer, 3 May 1944, contained in Report of Action Between LST Convoy and Enemy E-Boats, Night 4/27-28/1944 in the English Channel, COMLST GR32, A1061, RG38, NARA.
[102] Executive Officer LST515 to Commanding Officer, contained in Report of Action Between LST Convoy and Enemy E-Boats, Night 4/27-28/1944 in the English Channel, COMLST GR32, A1061, RG38, NARA.

[103] See 5th S-Boat Flotilla, Kriegstagbuch and Anlagen for April 1944 and See 9th S-Boat Flotilla, Kriegstagbuch and Anlagen for April 1944; T1022, 3211 and 3150, RG242, NARA.
[104] COMLST GR32 to COMINCH, US Fleet, 3 May, Report of Action Between LST Convoy and Enemy E-Boats, Night 4/27-28/1944 in the English Channel, COMLST GR32, A1061, RG38, NARA.
[105] Admiralty War Diary, 28 April 1944, RG38, A2180, NARA. Plymouth Command: War Diary, 28 April 1944, TNA: ADM 199/1393.

[106] See 5th S-Boat Flotilla, Kriegstagbuch and Anlagen for April 1944 and See 9th S-Boat Flotilla, Kriegstagbuch and Anlagen for April 1944; T1022, 3211 and 3150, RG242, NARA.
[107] HMS AZALEA report, 28 April 1944, contained in Report of Action Between LST Convoy and Enemy E-Boats, Night 4/27-28/1944 in the English Channel, COMLST GR32, A1061, RG38, NARA.

[108] See 5th S-Boat Flotilla, Kriegstagbuch and Anlagen for April 1944 and See 9th S-Boat Flotilla, Kriegstagbuch and Anlagen for April 1944; T1022, 3211 and 3150, RG242, NARA.
[109] War Diary, COM LST-FLOT10, 27-28 April 1944, A948, RG38, NARA.
[110] LST Group 30 Logs, LST51, 133, 134, 157, 285, 286, 502 towing Rhino Ferries 4, 5, 7, 8, 9, 12 and 15, NARA, via Dennis Hogan.
[111] Admiralty War Diary, 28 April 1944, A2180, RG38, NARA.
[112] US Army Naval Co-Operation, 28 April 1944, File 216, RG498, NARA.
[113] Admiralty War Diary, 28 April 1944, RG38, A2180, NARA. See also Report of Action War between LST Convoy and Enemy E-Boats on 28 April 1944 in the English Channel, COMTASKFOR125, Excerpt from Diary, Plymouth Command RG38 A1088.
[114] War Diary, COM LST-FLOT10, 27-28 April 1944, A948, RG38, NARA.
[115] Commanding Officer LST531 to Secretary of the Navy, 2 May 1944, RG38, A1061, NARA.
[116] War Diary, COM LST-FLOT10, 27-28 April 1944, RG38, A948, NARA.
[117] Admiralty War Diary, 28 April 1944, A2180, RG38, NARA.
[118] Report of Action War between LST Convoy and Enemy E-Boats on 28 April 1944 in the English Channel, COMTASKFOR125, Excerpt from Diary, Plymouth Command A1088, RG38, NARA
[119] LST Group 30 Logs, LST51, 133, 134, 157, 285, 286, 502 towing Rhino Ferries 4, 5, 7, 8, 9, 12 and 15, NARA, via Dennis Hogan.
[120] COMLST GR32 to COMINCH, US Fleet, 3 May, Report of Action Between LST Convoy and Enemy E-Boats, Night 4/27-28/1944 in the English Channel, COMLST GR32, A1061, RG38, NARA.
[121] Prime Minister to General George Marshall, 16 April 1944, Churchill Papers, CHAR 20/162/51-52.
[122] Prime Minister to President Roosevelt, No.688, 29 April 1944, Churchill Papers, CHAR 20/163/111
[123] See James Foster Tent, E-Boat Alert: Defending the Normandy Invasion Fleet, United States Naval Institute Press, Annapolis, 1996.
[124] Doenitz Interview, 20 July 1945, ETHINT-28, M1035, RG338, NARA.
[125] FdS Memorandum on Torpedo Attacks, 20 January 1943, TNA: ADM 223/28.
[126] Hinsley, Intelligence, p.454. See also use of Special Intelligence during Operation Neptune, TNA: ADM 223/267. p.166.
[127] HMS SALADIN report, 29 April 1944, contained in Report of Action Between LST Convoy and Enemy E-Boats, Night 4/27-28/1944 in the English Channel, COMLST GR32, A1061, RG38, NARA.
[128] Commander CTF125 to C-in-C, US Fleet, 6 May 1944, contained in Report of Action Between LST Convoy and Enemy E-Boats, Night 4/27-28/1944 in the English Channel, COMLST GR32, A1061, RG38, NARA.
[129] Transcript of Interview between CTF125 and CO HMS AZALEA, 29 April 1944, contained in Report of Action Between LST Convoy and Enemy E-Boats, Night 4/27-28/1944 in the English Channel, COMLST GR32, A1061, RG38, NARA.
[130] Director of Tactical, Torpedo & Staff Duties Division, 3 July 1944, TNA ADM199/261.
[131] C-in-C Plymouth to Naval Commander Western Task Force, 5 May 1944, TNA ADM199/261.