“S 47” in the Black Sea still without the armoured bridge – the Kalotte.
R boats (Räumboote in German)
Verkehr mit Kleinfahrzeugen (MFP) in the Black Sea
During Operation Barbarossa, Army Group South marched through the Ukraine towards the shores of the Black Sea. The forces that comprised the Army Group had been weakened slightly by the invasions of Yugoslavia and Greece resulting in greater reliance on troops from other Axis nations, arguably blunting Barbarossa’s spearhead. The port city of Odessa held out against the invaders for two months under siege before Soviet forces successfully evacuated, while the Crimea then became the scene of some of the fiercest fighting on the Eastern front during 1941. The prize, Sevastopol, came under German siege on 30 October 1941 and stubbornly refused to crack. Key to Soviet ability to hold both cities was the Black Sea Fleet, comprising one battleship, five cruisers, three destroyer Leaders, eleven modern destroyers, four old destroyers, forty-four submarines, two gunboats, eighteen minesweepers and eighty-four MTBs.
Opposing them was the Royal Romanian Navy comprising four destroyers, six fleet torpedo boats, one submarine, five Midget submarines, two Minelayers and seven MTBs. The submarine Delfinul was temporarily commanded by Kaptlt Hermann Eckhardt, who had occupied a shore position in Constanta in a bid to help train Romanian submarine crews. At least ten Germans served alongside the Romanian crew during April 1942. Eckhardt was later posted to U432 and killed when his boat was sunk on 11 March 1943. The Germans for their part could field only the six small riverine vessels of the Danube Flotilla. Initially, a German naval mission in Romania had provided cooperation between the Axis powers, but Barbarossa necessitated greater German commitment. Kriegsmarine control of the region rested at the highest level with Marinegruppenkommando Süd (MGK Süd), headquartered in Sofia, Bulgaria. Immediately below this office was Admiral Black Sea (Kommandierende Admiräl im Schwarzen Meer) to which the U-boat commitment would be directly added. The Black Sea was further divided into three regions – Ukraine, Crimea and Caucasus – with individual Seekommandanturen, responsible for coastal security and working alongside a bewildering array of Italian, Romanian, Bulgarian and Croatian naval units as well as a small Ukrainian volunteer unit.
On 26 December 1941, Soviet troops made seaborne landings on the northern coast of the Kerch Peninsula, establishing five bridgeheads up to one battalion in strength each. While huge resources were still engaged in battering Sevastopol, the Germans were momentarily thrown off balance by their enemy’s ability to land troops in force with naval artillery support. Sevastopol was still supplied by freighters protected by the Black Sea Fleet, who simultaneously used artillery to great effect on besieging Axis troops. Typical supply convoys were small: generally one or two steamers with a small escort. In Berlin OKW recognised the Soviet Navy’s dominance of the Black Sea and both U-boats and S-boats were committed to transfer to the region.
Debate followed within OKW as to the best means of relocating U-boats to the Black Sea. During the First World War, small UB and UC-class U-boats that had comprised the bulk of the Adriatic’s Pola flotilla, were transported in segments overland by rail: each boat requiring three wagons, one for each major component with further wagons for the conning tower, engines and batteries. Reassembly took approximately fourteen days before the boats were ready for sea trials. The same principle would be applied to the transport of six small U-boats from Germany, using the combination of rivers, roads or rail.
Initial investigations into overland transport by OKM’s Quartermaster Division reported that by December 1941 boats could be moved from the Elbe to the Danube on railroad cars which could accommodate small Type IIs, with their engines and conning towers removed. If carried by pontoon along the river system a Danube bridge, which was being preserved as a historical monument, would require demolition. The total transfer time was estimated at ten to twelve months, causing Hitler to dismiss the idea in a conference on 12 December and instead concentrate on the transfer of the S-boats from the 1st S-flotilla. R-boats of the 3rd R-flotilla would also be transferred using this method, beginning in May 1942. Eventually, two R-flotillas, one S-flotilla, two escort flotillas, three U-Jagd flotillas, one Artillerietrager flotilla, one transport flotilla and four landing flotillas would comprise the bulk of the Kriegsmarine surface deployment within the Black Sea, all bar the S-boats grouped within the 10th Sicherungsdivision.
Nonetheless in January 1942 Hitler returned to the idea of Black Sea U-boats, proposing that Germany solicit the cooperation of neutral Turkey. U-boats already within the Mediterranean could perhaps be exchanged for Turkish submarines within the Black Sea, or sold to the Turks, transferred into the Black Sea and then bought back by the Reich. The suggestion that this political complexity could be subverted by simply sending U-boats through the Dardanelles and the Bosporus Straits was strongly refuted by OKM as Turkey could only allow U-boats to enter the Black Sea by violating the Montreux convention of 1936 that gave Turkey full control of the Straits, which restricted the passage of military vessels not belonging to Black Sea states. Historically, it had been proven that the upper echelons of the Third Reich were relatively unconcerned with adherence to international treaties and protocols. Since the convention was working to Germany’s advantage by preventing British naval forces from entering the Black Sea and Russian forces from entering the Mediterranean, Germany stood more to gain from Turkey’s adherence to the agreement. Furthermore, the sale and resale of U-boats was discounted as, if the Turks agreed, it would be a thin deception displaying Turkish disregard for her obligations as a neutral power. A separate proposal to simply purchase existing Turkish submarines was also refused by OKM as they would require considerable conversion and upgrade to reach the standards required by the Kriegsmarine. Thus, with Barbarossa clearly not bringing the rapid defeat of the Soviet Union envisaged by Hitler during 1941, the transfer of an initial three Type II U-boats was once again proposed and accepted.
On 15 April 1942, three Type IIB boats – U9 and U24 of Pillau’s 21st U-training flotilla and U19 of Gotenhafen’s 22nd – were chosen. All three boats had seen action within the North Sea and English Channel during the early months of the war before relegation to training duties. The same limitations in action noticeable in 1939 and 1940 would become evident once more, including a poor maximum surface speed of 13 knots. Underwater the boats could reach 7 knots, though only briefly before batteries ran dry. Armed with three bow tubes, a maximum of five torpedoes or twelve TMA mines could be carried. Crewed by between twenty-two and twenty-four men, the Type IIB originally sported a 20mm deck weapon though improvements within the Black Sea would later see some equipped with Wintergarten flak platforms abaft the conning tower.
On 15 April the three U-boats were gathered in Stettin awaiting the clearance of ice that marred the passage to Kiel. The entire transfer to their planned base at Constanta, Romania, was expected to take twenty-six weeks, each U-boat despatched in three to four week intervals. If the schedule was adhered to, they could be operational in the Black Sea before the Danube froze for winter 1942. In Kiel’s Deutsche Werke shipyard, they were stripped of as much as possible: conning tower, diesel engines, electrical motors, batteries, decking and other smaller items lifted out to reduce hull weight.
The upright hulls were attached to shallow-draught rafts, each constructed from five pontoons, which, once complete, were rotated 90 degrees until the U-boat lay on its starboard: in itself a complex task, manoeuvring the 250-ton hulls by way of careful partial flooding of the pontoons and U-boat trimming tanks. Beginning with U24 the rafts were then moved through the Kiel Canal to Hamburg and from there upstream along the Elbe River to Dresden. In the suburb of Übigau the pontoons were lifted by slipway from the water and the U-boat hull craned across to low-bed transport trailers fitted with solid rubber tires and pulled by heavy Kuhlemeyer trucks, each trailer pulled by four separate trucks. The Kuhlemeyer operated in various configurations: in line, on a single broad front or with two before and two behind dependent on the road and weather conditions at the time. The Deutsch Amerikanischen Petroleum Gesellschaft had previously used the vehicles to transport small tanker ships overland to the Danube and so the same principles were applied to the U-boats. From the slipway the autobahn that stretched to Ingolsdtadt was easily accessible. Travelling at a maximum of 8km/h the U-boat transport occupied 600 men and took fifty-six hours of laborious constant travelling – drivers changed without bringing the convoy to a halt. The manpower included shipbuilders, transport drivers, traffic police, security troops and engineers assigned to remove any potential obstacles along the route. Workshop vehicles, communications vehicles and tanker trucks laden with fuel accompanied each U-boat transport enabling supply and replenishment of the heavy Kuhlemeyer trucks. Each bridge to be traversed was examined by structural engineers before the U-boat was carried across and, if necessary, reinforced for the U-boat’s passage.
Once in Ingolstadt the boat was returned to the pontoons which had been shipped by rail from Dresden and then towed along the Danube River by tug boat to Galati, Romania. There the boats were reassembled, returned upright by once again using trimming tanks and the flooding of pontoons.
The Kriegsmarine already planned to strengthen the U-boat presence within the Black Sea to more than just three. Not only was it considered an ideal prospective training ground for future crews once Russia was beaten – the destruction of the Soviet Black Sea Fleet expected complete by November 1942 – but Hitler decreed in conference with Raeder on 26 August 1942 that the presence of an increased U-boat flotilla would have a ‘favourable political influence’ on pro-Axis Turkey. Correspondingly three more Type IIBs from the 21st and 22nd U-training flotillas were chosen for transfer while the original trio was still in transit. During September U18, U20 and U23 were taken to Kiel to begin an identical process of deconstruction and transport toward Constanta. Ironically, although the second trio of U-boats would find their passage interrupted and delayed for several weeks due to ice on the river, it was the summer heat that set back the first group – their transit by way of the Danube deferred due to drought causing low water level at Ingolstadt.
After a belated arrival, each boat took between forty-two and forty-five days to reassemble in Galati, recommissioned into the Kriegsmarine once complete and joining the newly established 30th U-boat Flotilla. From the shipyard they continued along the Danube, arriving eventually in Sulina within the Danube Delta, travelling onward in convoy with other craft into the Black Sea and on to the Romanian naval base at Constanta, the new home of the 30th U-boat Flotilla. Oberleutnant zur See Klaus Petersen’s U24 was the first boat to complete the journey: recommissioned on 14 October 1942 and reaching Constanta at 10.33 p.m. on 16 October. Kapitänleutnant Hans-Joachim Schmidt-Weichert’s U9 was recommissioned on 28 October, reaching Constanta on the penultimate day of the month while ObltzS Hans-Ludwig Gaude’s U19 was commissioned on 9 December and arrived at 30th U-boat Flotilla headquarters on 30 December.
As early as 6 October 1942, the flotilla’s operational plans had been outlined by SKL. German troops fighting in the Crimea required supply by sea and land, the former under threat from Soviet naval and aerial attack:
Adopt the view that southeastern Black Sea ports will remain in Russian hands for some time. They are, to a limited extent, jumping off bases for nuisance raids on our supplies and coast. Traffic of warships and merchant vessels converges off them.
This sea area (after the probable fall of Tuapse, mainly off Poti and Batum) is a favourable operational area for our U-boats; attack on warships to be the principal objective [original emphasis], for the moment, down to and including destroyers. Given favourable opportunities, attacks on submarines are likewise unrestricted. U-boats are to regard attacks on enemy supply lines off the coast as a secondary task but should nevertheless take advantage of any favourable opportunities e.g., they might on occasion – for direct support of Army operations – concentrate their attack on supply traffic.
On the first operation the commanders will have to devote a certain amount of time to observing enemy warship movements and the naval situation within the operational area. Moreover for subsequent operations after the first surprise attack, enemy reactions will have to be taken into account.
The simultaneous employment of German and Italian U-boats in the same area is impracticable. An endeavour will be made to remedy the low operational efficiency of Italian boats by having them towed to the operational area by German U-boats. Such operations will depend on the outcome of discussions. The operational areas should be so divided that the Italians operate immediately to the northwest of our U-boats, primarily against merchant shipping, Italian boats will make the return passage on their own. It will thus be possible to occupy a fairly long coastal patrol line enabling us to observe traffic and at the same time attack warships off the most southerly bases, protect supplies from Russian attacks, prevent interference with merchant shipping off the coast further to the northwest and give direct support to German Army operations on the Caucasus front.
Operations would gain considerable support from cooperation with the Luftwaffe. Concentrated air attacks on the principal bases of the Russian Fleet would force it to put to sea and so create an opportunity for our U-boats to attack. There is, however, little hope of this until the Luftwaffe is free of other tasks. The findings of daily reconnaissance could for the time being be utilized for U-boat operations.
To extend U-boat operations involving a relatively long approach passage, a jumping off base is being established in Theodosia or Kerch, so that boats can be put in for a brief spell between two operations for restocking with torpedoes, refuelling, reprovisioning etc., and even to relieve certain sections of the crews.
Based in Bucharest, V.A. Hellmuth Heye (Admiral Black Sea until early November 1942) would later add his own addendum to these instructions, relating his opinion to 30th U-boat Flotilla officers that the Soviet Black Sea Fleet’s ‘excellent morale and capabilities’ would make its expected destruction by Luftwaffe harbour attacks unlikely. However, the presence of the U-boats would not only tie down Soviet naval forces and keep them away from army supply convoys, but also prevent the likelihood that – if faced with defeat as the land war passed them to the east – Soviet naval units could dismount their vessels’ heavy weapons for use ashore. Therefore every ship destroyed was also of direct benefit to the land war.
The 30th U-boat Flotilla was established under the command of veteran U-boat skipper Kaptlt Helmut Rosenbaum. Rosenbaum had joined the Reichsmarine in 1932 and served first aboard light cruisers as a Fähnrich zur See before transferring to the U-boat service in time to make more than one patrol as a watch officer during the Spanish Civil War. In February 1939 he took command of the Type IIA U2, making two war patrols within the North Sea before being transferred to skipper the new Type VIIB U73. Aboard this boat Rosenbaum sank eight ships within the Atlantic before breaking through the dangerous Strait of Gibraltar and scoring his largest victory on 11 August 1942 when he torpedoed and sank the aircraft carrier HMS Eagle. Rewarded with a Knight’s Cross, Rosenbaum was brought ashore and posted to Romania and command of the 30th U-boat Flotilla, his flotilla engineer the talented Kaptlt (Ing.) Heinz Bruns previously of U75. Like the Arctic U-boat command, Rosenbaum was not directed by BdU but rather formed an operational staff within the Admiral Black Sea command: Heye replaced in November by VA Robert Witthoeft-Emden. Unlike most other flotilla commanders, who were primarily responsible for logistical matters, Rosenbaum would also exercise tactical control over his small flotilla. Rosenbaum conferred with Heye upon arrival in Romania, his superior emphasising the importance of attacking naval targets, such Russian merchant convoys that could be found likely to be not only very small and in shallow waters, but heavily defended and flanked by anti-U-boat minefields, best left to the attentions of S- and R-boats.
Meanwhile flotilla headquarters was established in Constanta, administrative and stores buildings provided near the harbour’s North Pier at the end of the main railway spur. The crews and staff were accommodated streets away within the town itself. Constanta, already fortified by the Romanians, had received German reinforcement since the country’s 1940 entry into the Axis alliance. The German mission in Bucharest planned defences at key points along the Black Sea coastline, modernising Romanian coastal artillery that was largely obsolete. During the winter of 1940 three 280mm cannon were situated at Constanta: the backbone of the Tirpitz naval battery, completed with 75mm and 20mm flak weapons. The battery – and its surrounding land defences – was served by 700 Kriegsmarine personnel of the 613th Marine Artillerie Abteilung, and by the time the 30th U-boat Flotilla began operations, over 3,700 German troops were stationed in Constanta alongside nearly 40,000 Romanian troops. The Tirpitz battery saw action against Soviet Naval Forces only once, on 26 June, 1941, when destroyers Moskva and Kharkov fired 350 shells into the harbour and its railway station. Several tanker carriages were destroyed before Romanian artillery and destroyers returned fire. The Tirpitz battery added thirty-nine shells to the battle, lightly damaging Kharkov and panicking the crew of Moskva enough with near misses that she ran onto a minefield and sank killing 331 of the 400 crew.
Petersen’s U24 sailed operationally on 27 October, escorted from harbour by three minesweepers and destined for the south-eastern waters off the Georgian coast. The three Soviet naval harbours of Batum, Poti and Sokhumi were considered the most promising areas for operations against military targets, although with little intelligence available on enemy dispositions – including minefields – within the area, Petersen was expected to spend time on reconnaissance for future U-boat operations.
Three days from harbour U24’s bridge watch sighted smoke but failed to locate the corresponding vessel. On 1 November Petersen attempted an attack against a Soviet submarine: two shots fired and both torpedoes failing, probably missing due to excessive range. It was a pattern repeated throughout the short patrol. On 5 November Petersen made a surfaced attack on what he identified as a small tanker – in actuality Soviet minesweeping trawler T492. At 7.18 p.m. a single G7e was fired that passed beneath the target ship, machine-gun fire from the trawler forcing U24 to dive and seek a second firing position. Just over two hours later, Petersen fired a G7a steam torpedo, which hit below the Soviet’s bridge, although a defective pistol rendered the torpedo a dud. Determined to make his attack count Petersen surfaced and opened fire with his deck-mounted 20mm cannon, the trawler returning machine-gun and rifle fire. Following at least one good hit on target, a magazine jam brought the attack to a halt and once again U24 was forced to dive away. Torpedoes exhausted, Petersen returned to port reporting his boat’s echo-sounder out of action and at least ten days repair required to repair gunfire damage to the conning tower. Petersen was ordered to return via the Turkish coast: reporting ‘lively merchant shipping traffic’ running near neutral waters.