Korvettenkapitän Rudolf Petersen, Führer der Schnellboote
S67 sporting the experimental plexiglass bridge armour. Imperfect due to its high reflectivity, research ended with the armoured Kalottenbrücke (skullcap).
September was something of a high-water mark for Petersen’s western S-boats, able to field twenty-six operational craft. However, facing them were 324 MGBs, MTBs and MLs of the Allied coastal forces, not to mention larger warships and those of the auxiliary flotillas. The Luftwaffe had stopped its part in minelaying, diverted instead to defensive tasks or the resumed bombing of British cities. Bad weather prevented further S-boat operations until 7 October when all four flotillas laid mines once more along the east coast, S93 damaged outbound by another mysterious explosion within the crank casing and returning to Ijmuiden with S127 escorting. Hours later S83 was also compelled to return with engine damage, in company with S62.
Intelligence reports indicated that the British were not only aware of the minefields laid by S-boats, but also had developed a counter to the new fuses being deployed, and Petersen reverted to his trusted method of alternating torpedo and minelaying patrols, not informing MGK West of his decision but trusting to the level of autonomy that he held over S-boat operations.
Following a period of bright moonlight, the first torpedo mission took place on the night of 23 October using a massed force of twenty-seven boats from 2nd, 4th, 6th and 8th S-flotillas, led by KK Heinrich Erdmann – FdS Chief of Staff – aboard S94. While once this formidable force would have seemed assured of victory, in October 1943 they ran into the overwhelming might of British convoy defence while attacking convoy FN60 (Phase 10) near Cromer. The incoming S-boats were detected by British bombers laying minefields in German waters, placing defences on high alert. The Germans arrived near the estimated convoy location, but were actually well astern of its path as FN60 was two hours ahead of schedule. The escort comprised destroyers HM Ships Campbell, MacKay, Worcester, Eglington and Pytchley as well as six MGBs, two ML and two MTBs. While shore radar tracked the inbound Germans, HMS Pytchley detected S-boat traces on shipboard radar and opened fire at 2318hrs. The sole German success was the torpedoing of straggling trawler HMT William Stephan by Kptlt Witt’s S74, four survivors rescued by their attacker. The remainder of the night was a German disaster.
All nine boats of the 2nd S-flotilla, including S94, managed to outpace pursuit and break free. Four boats of 6th S-flotilla, led by Kptlt Obermaier aboard Führerboot S76, suffered severe damage in the struggle that followed. Obermaier was forced to transfer to S114 after radio failure and, following Witt’s sinking of the British trawler, several S-boats suffered torpedo failures, many crewmen wounded by British cannon fire. Likewise, the six 8th S-flotilla boats took several hits before escaping under a hail of bullets and star-shells. The eight boats of the 4th S-flotilla bore the brunt of the enemy’s fury. One group – S88, S63, S110 and S117 – led by KK Lützow in S88, came under fire by HMS Worcester, a 4.7in shell hitting S88 directly and badly damaging her as she slewed to a halt. The bridge was wrecked and the bodies of Lützow and skipper Obstrm Heinz Räbiger were seen lying in the wreckage, both with severe head injuries. Fire quickly spread after more British shells landed, fuel tanks exploding as survivors sprang overboard, nineteen rescued by the British, two of whom later perished. Shell splinters had also knocked out one engine aboard S63, which was then bracketed by fire from HMS MacKay while laying smoke and dropping delayed action depth charges behind them. S63 was straddled with 6pdr fire and sank, LzS Dietrich Howaldt and twenty-three of his crew rescued, three as prisoners of the British.
There were no further missions in October as bad weather hampered a renewal of operations. Following the loss of Lützow, S120 skipper Kptlt Albert Causemann stepped in as interim commander of 4th S-flotilla until November when KK Kurt Fimmen, former commander of S26, and more recently captain of torpedo boat T16, came in to take the flotilla helm.
Kriegsmarine command proposed replacing some torpedo gear with extra guns to combat the increasingly effective British coastal forces, but Petersen strongly objected, despite recent losses. As if to confirm his faith in the torpedo, the 5th S-flotilla found convoy CW221 during the morning of 3 November and ObltzS Stohwasser’s S138 hit SS Storaa amidships. Heavily laden with tons of iron tank-tracks and aircraft parts, the 1,967-ton ship went straight down with twenty-two of her thirty-six-man crew killed. ObltzS Kolbe’s S100 also hit 811-ton SS Foam Queen carrying coal to Poole, her stern blew off as stored ammunition exploded, and she sank immediately as the engines also fell into the sea. What remained afloat was later towed to Dover and beached. ObltzS Jürgensmeyer’s S136 also torpedoed collier SS Donna Isabel, the torpedo hitting the engine room, but failing to explode and passing clean through the ship, before the eyes of the merchant’s chief engineer. Badly holed, the ship took one hour and twenty minutes to go down, the crew abandoning her without loss of life to be rescued by ML141. Though the S-boats had experienced a successful night, the statistic of only four hits from twenty-three torpedoes fired was sobering. For some commanders present these had been the first live torpedoes they had ever fired, Baltic training cut short by demand for front-line crews.
The following night the four Netherlands flotillas mounted another combined minelaying mission near Orfordness. Twenty-four boats sailed, two aborting with engine damage. The first group of 2nd S-flotilla laid twenty-eight UMB mines before encountering FN70 (Phase 10), its escorts unable to detect the S-boats on radar due to atmospheric interference. S80 and S89 both fired double torpedo shots, hitting and damaging 2,841-ton collier SS Firelight, blowing away most of the ship’s bow. S62 hit and badly damaged commodore ship MV British Progress. This 4,581-ton tanker was the first victim of an S-boat launched FAT torpedo. The FAT (Federapparat Torpedo) ran a wandering course with regular 180° turns, designed as a longdistance unguided weapon for use against densely packed convoy traffic.
The second group from Feldt’s flotilla unsuccessfully skirmished with escorting destroyers before breaking away from the action. Elsewhere, all minelaying was completed to plan, boats heading back to base as morning approached. The 6th S-flotilla’s S116 suffered engine failure, while S114 had another mysterious explosion within the crankcase shortly afterward. With dawn approaching, the flotilla boats sailed at reduced speed in mutually defensive posture, inevitably attacked by six RAF Beaufighters at 0725hrs. Oberleutnant zur See Herbert Witt’s S74 took multiple hits and lost all manoeuvrability, three men killed by cannon fire before the boat was abandoned and sunk by a torpedo from S135. S116 and S91 were also damaged as urgent appeals for Luftwaffe cover were denied. Eventually, at 0830hrs, six German fighters took off to assist, by which time the Beaufighters had gone.
During February 1944 KK Klaus Feldt departed 2nd S-flotilla, replaced as commander by Kptlt Hermann Opdenhoff, the two officers exchanging roles as Feldt returned to Germany to head the S-boat training division (Schnellbootslehrdivision) formed under Opdenhoff’s command in November 1943. Training division headquarters were established in Swinemünde, forming an administrative umbrella over all S-boat training units. Upon Feldt’s arrival these comprised 1st Detachment (Abteilung) in Swinemünde, and 1st S-training Flotilla (Schnellbootsschulflottille) centred on tender Adolf Lüderitz. By June 1944 a second detachment was established in Kaseburg and two more flotillas with tenders Carl Peters and Tsingtau.
Bad weather prevented many more Channel operations in 1943. A foray by 5th S-flotilla near Beachy Head on 1 December sank HMT Avanturine with a single torpedo, ObltzS Ahrens hitting the 296-ton trawler while it was under tow by HMT Peter Carey. The year had seen a drastic fall in S-boat success within the Channel: twenty-six merchant ships were sunk in total. For the S-boats, eighty-four men had been killed in action, fifteen more severely wounded and thirty-seven lost as prisoners of war. Fifteen S-boats had been sunk. Coupled with this was a perceptible increase in British home-water seapower. During May 1943 U-boats had reached their peak strength with 118 U-boats at sea, yet they also suffered their most grievous losses with forty-one destroyed in action. Dönitz conceded defeat and the U-boats withdrew from the Atlantic to revive their numbers, never to return in strength again. The Battle of the Atlantic had been lost and although U-boats continued to sail and sink ships, Allied naval and air power had prevailed to such an extent that many destroyers were no longer required for convoy protection, able instead to concentrate their efforts in coastal waters.
Petersen’s Channel force received recognition and reinforcement as the newly established 9th S-flotilla, under the command of Kptlt Götz Frhr von Mirbach, arrived in the Netherlands with new boats S130, S144, S145 and S146, while on 1 January 1944, flotilla commanders KK Bernd Klug and KK Klaus Feldt were awarded the Oak Leaves to their Knight’s Crosses.
Invasion fever still prematurely gripped OKW. Petersen countered proposals that S-boat control be devolved from FdS to local commands in the event of Allied landings, reasoning that optimal S-boat conditions for success were only possible under centralised command: Führer der Schnellboote. Through this office he would receive orders from MGK West and co-ordinate his boats accordingly. He also continued to resist the conversion of S-boats into heavier gun platforms, Dönitz himself questioning his tactics by declaring 37mm guns inadequate, instead proposing 50mm or 55mm fixed weapons, even the possibility of incendiary ‘Greek fire’ weapons. This would eliminate S-boat speed and manoeuvrability and while Petersen continued to resist such moves, he continued the war with what means he possessed.
By 1 January Petersen had forty-six operational boats spread between six flotillas in the west and five more refitting in German harbours. The Luftwaffe had promised a slight increase in available reconnaissance through the use of radar-equipped Junkers Ju88 aircraft. Petersen’s decision to abandon large scale minelaying met with belated approval from MGK West, though SKL was keen to point out that ‘a mine is a permanent source of danger; a torpedo, once fired, loses its effect’.
Rough seas prevented operations until 5 January when seven 5th S-flotilla boats attacked an eastbound convoy. Divided into three Rotten they had narrowly escaped damage after mines exploded near Führerboot S100 while departing Cherbourg. The S-boats found convoy WP457 between Land’s End and The Lizard during early morning darkness. Obersteuermann Richard Grüger’s S143 fired a single first torpedo as Plymouth radar reported the unidentified contacts closing fast. Grüger hit 1,408-ton SS Solstad headed to London with coal, the ship sinking in less than three minutes with five dead. ObltzS Hinrich Ahrens aboard S142 reported a ‘2,000-ton’ freighter also hit and sinking, while ObltzS Hans-Jurgen Stohwasser’s S138 torpedoed and sank the 545-ton escorting trawler HMT Wallasea. The Rotte comprising S84 and S141 both torpedoed 403-ton MV Polperro, the small collier carrying coal from Manchester and sinking with all eight merchant crew and three gunners. The final confirmed sinking was 1,990-ton MV Underwood carrying a cargo of nine fully fuelled invasion craft which burst into flame as the ship sank, fourteen of the twenty-three people aboard killed. Klug’s flotilla sailed for Brest as the scattered ships of WP457 retreated into Mounts Bay. The attack against WP457 had been the first use of the new TZ3 magnetic torpedo pistol and, though successful, Petersen was critical of the number of single torpedoes fired at excessive range.
During 16 January Klug’s flotilla attempted to repeat their success and attacked westbound convoy PW461 near Lizard Head. Although torpedoes were fired, HM Ships Talybont and Brissenden fended the S-boats off in bad visibility and the convoy was unharmed. Once again the 5th S-flotilla sailed to Brest before returning to their home port of Cherbourg.
Hinrich Ahrens’ S142 was at the forefront of the attack on CW243 southeast of Beachy Head by Klug’s 5th S-flotilla on the night of 30 January. Once again divided into three Rotten, one attacking from inshore of the convoy, Ahrens hit and blew the bow off escort HMT Pine which continued to fight back, later sinking under tow to shore. Ahrens also hit and sank 806-ton collier SS Emerald with the third torpedo he fired, his fourth a failure. The other half of his Rotte, ObltzS Hans-Jurgen Stohwasser’s S138, torpedoed 1,813-ton SS Caleb Sprague, twenty of twenty-seven crew and three out of four gunners lost.
During early February Kptlt von Mirbach’s 9th S-flotilla moved from Vlissingen to Dunkirk, from where it was planned to operate alongside Cherbourg’s 5th S-flotilla against the south coast. Reinforcing this area, Petersen was forced to lose strength from the Netherlands. Following the successful Soviet winter offensive near Leningrad, OKM feared a resurgence of the Soviet Baltic fleet and ordered 6th S-flotilla removed from the west and transferred to the Finnish Bight. Eight boats departed on 7 February, S128 and S135 following later, once fitting of 40mm flak weapons was completed in Rotterdam. Petersen then faced yet further potential reduction as OKM vacillated over decisions to move at least two of his flotillas to the harbours of Bordeaux, Arcachon, Bayonne and Saint-Jean-de-Luz, amid fears of an Allied landing on the Iberian Peninsula. However, the idea was eventually dismissed.
On the night of 12 February the 8th S-flotilla mined the waters southeast of the Humber with thirty-six LMB mines, S99 and S65 sighting minesweeping trawler HMT Cap d’Antifer and sinking her with torpedoes leaving no survivors from the twenty-four crew. Two nights later both the 2nd and 8th S-flotillas sailed from Ijmuiden, the former to lay mines, though they were intercepted and forced away by HM Ships Shearwater and Mallard off Southwold. Returning to harbour they joined a battle between three German minesweepers and British MTBs near the harbour. S89, S98, S92, S80 and S67 raced into the attack, hitting and damaging several British vessels, the commander and three ratings killed aboard MTB444. During the confused melee, minesweeper M3411 was sunk by torpedoes from MTB455, and S89 so severely damaged by cannon fire that she was later towed into harbour, badly holed and low in the water, both torpedoes fired to lighten the hull as the crew doused fires in the stern.
Meanwhile, KK Felix Zymalkowski’s 8th S-flotilla were tasked with finding enemy MGBs in the vain hope of capturing one to obtain intelligence regarding British convoy routes, Petersen’s Luftwaffe intelligence having dried up. The same MTB groups that had tangled with Feldt’s flotilla now crossed paths with S93, S64, S117, S127, S129, S85, S133, S99 and S65 as they retreated to Lowestoft. The S-boats were in isolated Rotten and swift and accurate gunfire from the MTBs forced a path through the German vessels, damaging S99 and S133 and killing one man.
It had been an entirely unsuccessful mission as was the next one for 8th S-flotilla on 22 February when HMS Garth engaged the eight boats with cannon fire. Six torpedoes arced toward their attacker, all of them missing, and in the confusion that followed ObltzS Karl Rindfuß’ S128 collided with LzS Karl Boseniuk’s S94, killing one man. Both boats were so severely damaged that they were scuttled. The two young commanders’ inexperience lay at the heart of the disaster. Two nights later, after successfully laying mines, the flotilla torpedoed and sank 2,085-ton SS Philipp M from convoy FS71 (Phase 12). Laden with coal, the torpedo hit her starboard side, a vivid blue flash seen by ships three miles away. Her back was broken, and she sank within three minutes as the crew abandoned ship on rafts, their attacker being seen to approach at high speed from astern and then shut off engines and drift near a sandbank until lost in the darkness.
March and much of April saw disappointing mission results and increasingly frequent collisions. Bad visibility, strong enemy action and inexperienced S-boat reinforcements all contributed to the consistent failures. Meanwhile, Allied air power was directed against the S-boat harbours, Ijmuiden being raided by the USAAF 9th Air Force on 25 March. While the bunkers were not penetrated, they took heavy damage, other buildings used by 6th S-flotilla were completely burned out, and S93 and S129, moored outside of the protective shelter, were obliterated. To compound problems, a lighter was sunk immediately outside the bunker entrance, reducing access to during high water until the wreck could be removed.
On the night of 18 April S64 took a direct hit in the starboard torpedo tube and the midships-mounted twin machine guns while the 8th S-flotilla laid mines near Great Yarmouth. S133 was also hit, the shell exploding in the captain’s empty cabin, the boat already having suffered engine failure following another crankcase explosion. To the west that same night, the 5th S-flotilla was fired on by HMS Middleton and MTBs while also minelaying in the Channel. One man was killed in S141’s engine room before the flotilla escaped back to Cherbourg, avoiding MTBs attempting to head them off.
The pattern continued with S-boats taking casualties and damage with little recompense. On 24 April the Dutch tug Roode Zee was sunk defending CW264 near Dungeness, the only success thus far that month. Ordered to reconnoitre the Channel following yet another invasion scare on 26 April, S147 of the 9th S-flotilla was sunk by a direct hit from French destroyer La Combattante southeast of the Isle of Wight. The French ship closed the burning S-boat in order to rescue survivors, but only had time to pull one man aboard before hydrophone operators reported the approach of other S-boats, the destroyer moving away. S147’s skipper, LzS Bernhard Theenhausen, and ten men were later picked up, thirteen others killed.
However, S-boats were still dangerous. On 27 April six boats of the 5th S-flotilla and three of the 9th were ordered to sail against an enemy convoy reported by one of the infrequent Luftwaffe spotting missions. En route to their target area, S136 and S138 reported torpedo hits on an enemy destroyer, S100 and S143 claiming a 1,500-ton freighter hit and on fire. However, it was the 9th S-flotilla Rotte S130, S145 and S150 that wreaked the most havoc. They stumbled upon eight large tank-landing ships travelling in convoy as part of Exercise Tiger. An American simulation of the planned assault on Utah Beach, the eight LSTs were part of the mock ‘build-up’ phase, carrying vehicles and troops of the 1st Engineer Special Brigade. The exercise had already been marred by ‘friendly fire’ casualties from live ammunition fired by HMS Hawkins. Used to accustom men to the sights, sounds and smell of combat, a timing misunderstanding had sent several landing craft into the inferno before the British ship ceased fire.
The LSTs of convoy T4 were escorted solely by corvette HMS Azalea, a second escort HMS Scimitar having been damaged in a collision with an infantry landing craft the previous night and not replaced. Tragically, the incoming S-boats were sighted by both British radar and coastal gunners, the latter under orders not to fire lest they betray the area’s level of coastal defence, the former relaying the news to Azalea, who then failed to pass the information onward, assuming incorrectly that the American vessels had received the same message, evidently unaware that they operated on a different radio frequency. In fact, radar echoes of the incoming S-boats were detected aboard one of the slow moving LSTs, but the operator assumed they belonged to the convoy. Luck was with the Germans.
Oberleutnant zur See Gunther Rabe’s S130 and ObltzS Franz Behr’s S150 both fired torpedoes at LST507, some failing to explode, before one from S130 blew a hole in the ship’s side, setting her on fire. Shortly afterward LST531 was also hit, this time by Behr, and LST511 torpedoed as well but by duds. Oberleutnant zur See Hans Schirren’s S145 hit LST289, destroying the crew’s quarters, rudder and stern guns, although flooding was soon under control and the ship made it to Dartmouth under its own power. The remaining LSTs scattered as the three S-boats withdrew. Behind them they left a scene of devastation with at least 638 American army and naval personnel believed to have been killed, hundreds drowned under the weight of their equipment as they abandoned the burning ships. Even official figures vary as to the final death toll, possibly rising to 946, although news of the disaster was immediately withheld lest it betray the impending invasion of France. More American troops were killed that night than during the landings on Utah Beach in June 1944. All of the S-boats returned without damage.
These were, however, the last torpedo sinkings of the first half of 1944, the S-boats suffering casualties elsewhere. On the night of 13 May ObltzS Walter Sobottka’s S141 was sunk by La Combattante, the skipper and five survivors rescued. Amongst the eighteen men killed was LzS Klaus Dönitz, eldest son of Grossadmiral Karl Dönitz. A week later, ObltzS Günter Rathenow’s S87 was severely damaged by two Swordfish aircraft following completion of a successful minelaying mission. The boat sank, with Rathenow and most of his crew later rescued, two others killed and one listed as missing in action. Their mines accounted for HMT Wyoming and Dutch minesweeper Marken during the same night. American minesweeper USS Osprey was also lost to an S-boat mine on 4 June near St Catherine’s Point. The explosion blew a hole in the forward engine room, with six men killed. This was, in fact, the first casualty of Operation Overlord, the minesweeper engaged upon sweeping channels for impending invasion traffic.
On 30 May 1944 Kptlt Bernd Klug left the role of 5th S-flotilla commander, and was replaced by Kptlt Kurt Johannsen. Klug moved over to Petersen’s FdS staff as chief of staff, his predecessor KK Heinrich Erdmann departing to command destroyer Z30.
Air power continued to take its toll on Petersen’s S-boats; S100 was bombed and one man severely wounded in the early morning of 24 May, and S172 and S74 were both trapped inside the S-boat bunker in Boulogne Harbour following American bombing throughout the Pas de Calais. Although the S-boats were protected from damage, a shelter door was blown off, blocking the entrance to one of the double-berth pens. Though he could not know it, the intensified Allied air offensive heralded the long-feared invasion: Operation Overlord was about to begin.