On 5 July 1942, the German battleship Tirpitz, sailing as part of a squadron under the command of Admiral Otto Schniewind to intercept convoy PQ 17, was attacked by the Soviet submarine K-21, commanded by Captain Second Rank Nikolai Lunin. The submarine fired four torpedoes from a considerable distance. The result of the attack was not directly observed by Lunin, but the sounds of explosions were noted, which he interpreted as the result of torpedo hits. This was the basis for Soviet press claims that the battleship had been damaged. However, no torpedo hits were noted on the German squadron, and moreover, the attack itself was not detected. The German ships continued on their original course for approximately five hours, after which they turned back due to the inherent riskiness of the operation and the futility of continuing it against a convoy that had effectively ceased to exist as a unified entity.
In the Soviet Union, literature aimed at the masses was dominated by an opinion of the success of the attack. This was based on the Sovinformburo report and wartime press articles. The historiography of foreign countries initially concurred that the Tirpitz had not been struck by torpedoes, given the absence of documentary evidence attesting to the success of the attack. This evidence was not present in German documents or the memoirs of the participants on the German side. Following the return of the squadron, the battleship Tirpitz did not require repairs. A British-led team, including a Soviet specialist, conducted an examination of the hull of the battleship, which had been sunk in 1944. The examination revealed no evidence of torpedo hits or repairs on the ship. A contemporary reconstruction, based on the fullest available evidence, demonstrates that the attack had no theoretical possibility of success, given that the torpedoes were launched from a distance exceeding their maximum range. Nevertheless, the event is of significant historical importance to the Russian Navy, as it represents the only instance of Soviet submariners launching an attack against a heavy (larger than a destroyer) enemy warship.
Background
On 27 June 1942, the convoy PQ 17, one of the Arctic convoys that delivered weapons and resources necessary for the war effort to the USSR, commenced its journey from Iceland to Arkhangelsk. The 35 transports of the convoy carried cargo consisting of 297 aircraft, 594 tanks, over 4,000 vehicles and more than 156,000 tonnes of other cargo. Convoying this convoy entailed a significant degree of risk. The German aviation, which had numerical superiority in the Barents Sea area, was able to operate around the clock due to polar day and favourable weather conditions. The utilisation of enemy submarines and surface ships was also greatly facilitated by this circumstance. Nonetheless, for political reasons (in the summer of 1942, the situation at the front for the Soviet Union was critical and the country was in dire need of assistance), the British War Cabinet, headed by W. Churchill, decided to send the convoy. Its protection was provided by a close protection force of 19 warships and two submarines, a close protection cruiser force of four heavy cruisers and two destroyers, and a long-range protection force of an aircraft carrier, two battleships, two cruisers and 12 destroyers. Furthermore, a curtain of 13 submarines – comprising eight British, four Soviet and one French vessel – was positioned in the vicinity of potential German surface ship transit routes. At the same time, there were significant limitations on the use of these forces - the cruiser and long-range cover detachments could not operate east of Bear Island due to limited fuel reserves and the risk of enemy aircraft attack.
Simultaneously, the German military was formulating a strategy to thwart the convoy. In addition to the deployment of aircraft and submarines, the plan included the use of large surface vessels. The operation, designated as Rösselsprung, or "Horse Walk," permitted the utilization of all available heavy German naval vessels in Norway, including the battleship Tirpitz, heavy cruisers Admiral Scheer, Lützow, and Admiral Hipper, and their respective escorts.
On 1 July, the convoy was identified by German aerial reconnaissance, and by the evening of 2 July, the German ships commenced their transit from Trondheim and Bogen Bay to the forward base in Altafjord. The concentration was concluded on 4 July, with the heavy cruiser Lützow and three destroyers sustaining damage from rock landings and being withdrawn from the operation. Following the refuelling of the German squadron under Admiral Otto Schneewind in the afternoon of 4 July, the squadron was prepared to embark on a sea voyage. However, due to the lack of information regarding the location of the convoy's long-range covering squadron, the order to commence the operation was postponed. Concurrently, British intelligence had received reports of German heavy ships leaving the Trondheim base, but had no precise information on their further whereabouts. Given the speed of the German ships, they could have overtaken the convoy by the late evening of 4 July, risking the complete destruction of the convoy itself, as well as the forces of direct protection and close cover. In view of this, the First Sea Lord (Chief of the Naval Staff) of Great Britain, Admiral Dudley Pound, ordered on the evening of 4 July that the convoy be scattered and that the close-cover cruiser group be recalled to the west.
From that point on, Operation Rösselsprung was pointless, since the task of destroying the ships in the convoy, which were travelling separately, could be done much more effectively by submarine and air attack (which was eventually done). However, the Germans did not have full information about the convoy's break-up and believed it had split into two groups. On the morning of 5 July, after a German reconnaissance plane had spotted a long-range convoy escort moving westwards and posing no threat at that distance, the German command decided to launch the operation. At 11:55 on 5 July, the Tirpitz lifted anchor and the German squadron began to set sail.
German squadron before the attack
The German squadron that set sail consisted of the battleship Tirpitz, heavy cruisers Admiral Scheer and Admiral Hipper, destroyers Z4 Richard Beitzen, Z14 Friedrich Inn, Z24, Z27, Z28, Z29, Z30, and torpedo boats T7 and T15. Schneewind selected the fairway to the west of Rolvsøy Island as the optimal route for accessing the open sea, rather than the eastern skerry fairway prescribed by the higher command, which afforded access to the open sea in the vicinity of Porsangerfjorden. Schneewind's reasoning was that he considered the eastern channel to be more dangerous, both in terms of enemy submarines and the risk of mines being detonated. However, the route chosen by Schneewind took the German squadron into the area of the patrolling submarine K-21. At 16:06, the squadron commenced its transit across the open sea, increasing its speed to 24 knots and reorganising its formation in accordance with the anti-submarine defence protocol. This entailed a frontline formation with torpedo boats positioned at the flanks, preceding the heavy ships. Such a formation forced the submarine attacking from a forward course (and attacking fast surface ships was only possible from a submarine's underwater position) to lower its periscope and increase its depth to avoid being detected and attacked by the destroyers; but after passing the destroyers, the submarine had no time to organise a successful attack on the protected heavy ships. An attempt by a submarine to evade the order had a similar result - it simply did not have enough time to get within torpedo range of the attacked ships, the squadron literally whizzed past the submarine. To reduce the risk of torpedoing the destroyers, at 16:46 Schneewind ordered them to move in a small zigzag. The heavy ships continued to move without zigzagging. Furthermore, the Ar 196 seaplane was launched from the battleship Tirpitz with the objective of searching for enemy submarines. The squadron proceeded on a course of 30° (north-northeast), with the intention of reaching a distance of 25 miles from the coast as expeditiously as possible, given that the risk of submarine attack was greatest in this area. The distance between the heavy ships was initially 2,000 metres, but at 16:47 it was increased to 3,000 metres.
K-21 before the attack
In accordance with the operation to provide escort for the PQ-17 convoy, the Soviet Northern Fleet allocated four submarines to attack German heavy ships: K-2, K-21, K-22 and Shch-403. Of these, submarine K-21, commanded by Hero of the Soviet Union, Captain 2nd Rank Nikolai Lunin, was assigned position No. 2A, situated in proximity to the Norwegian coast and tasked with obstructing the fjord exits between the islands of Sørøya and Jelmsøya. By this time, Nikolay Lunin had accrued considerable experience as a submariner, having completed seven combat missions (five of which he commanded the Shch-421 and two the K-21). He claimed the destruction of eight enemy transports, although a post-war study of German documents revealed that only one ship, the 2975 grt displacement transport Konsul Schulte, had been sunk. By mid-1942, Lunin had developed his own tactical style, characterised by, among other things, active search for the enemy, maximum use of acoustic observation data, preference for firing from long and even extreme distances with full bow or stern salvos, poor use of the periscope after the initial detection of the target (the commander concentrated on observing only the selected target, which often led to the detection of only part of the enemy convoy or formation), excessive use of aft torpedo tubes, exaggerated assessment of the enemy's anti-submarine defence capabilities (which led to firing from long distances and frequent refusal to observe the results of attacks), careless attitude to facts and maximally optimistic assessment of the results of his torpedo attacks (all observations were interpreted solely to confirm success, and facts to the contrary were not taken into account.)
The submarine K-21 commenced its fifth combat cruise on 18 June 1942. The primary objective of the campaign was to detect and attack heavy enemy surface vessels. Consequently, four of the six torpedoes in the bow torpedo tubes were configured with a 5 m depth of travel setting, which ensured that deep-seated battleships and cruisers were hit in the vulnerable part of the hull below the armour belt. The remaining torpedoes (two in the bow torpedo tubes and four in the stern torpedo tubes) were set to a depth of 2 metres. On the morning of 19 June, the submarine was travelling in a surface position in low cloud conditions when it was attacked by an enemy aircraft. Two aerial bombs exploded approximately 30–40 metres from the boat. The concussion caused damage to the K-21, resulting in the inability to use the fast dive tank and equalisation tank No. 1. This limited the submarine's manoeuvrability in the underwater position. On 27 June, K-21 was subjected to a second attack by enemy aircraft. However, the bombs that were dropped near the board failed to detonate, limiting the damage to eight bullet holes in the light hull. On the night of 28 June, following the receipt of an order, K-21 proceeded to position No. 2A, where it conducted patrols over the following days, having no contact with the enemy until 5 July.
The attack
At 16:30, K-21 hydroacoustician A. Smetanin heard a noise, which he identified as the sound of ships' propellers. At that moment, the K-21 was in an underwater position at a depth of 20 metres and was sailing at a speed of 3 knots. The hydroacoustician reported that the target was located at a distance of 12 miles from the submarine, with a heading angle of 30° on the starboard side. The reconstruction presented by N. Skrynnikov and M. Morozov (hereinafter referred to as the reconstruction) indicates that the actual distance between the German squadron and K-21 at that moment was approximately 35 miles, with a course angle of 3°. This suggests that the German squadron proceeded directly towards K-21. The watch commander of K-21 at the time of the acoustic contact was Senior Mate F. Lukyanov, the boat commander was asleep in his cabin. At 16:40 K-21 surfaced under the periscope, but nothing could be seen on the horizon. At 17:00, the submarine altered its course in order to proceed directly towards the noise source. Concurrently, the periscope was elevated, through which an adversarial submarine, identified as a German U-boat, was observed approximately 4–5 miles away. This was in fact the upper masts of the German fleet, which, according to the reconstruction, were situated approximately 22 miles away. The capacity to observe vessels at such a considerable distance was a consequence of refraction over the surface of the sea. A torpedo attack was announced on the boat, and a command was issued to prepare torpedo tubes for firing. At approximately the same time, Lunin, who had been awakened by a messenger, entered K-21 control.
At 17:02, K-21 commenced a left turn, and at 17:10, it increased its speed to 5 knots, preparing to engage the enemy "submarine" with its stern torpedo tubes. At 17:12, Lunin altered the target identification, assuming that instead of a submarine, he was observing two torpedo boats in a ledge formation at a distance of 6–7 miles. He then proceeded to attack one of them, also utilising the stern torpedo tubes. In point of fact, Lunin continued to observe the tops of the masts of the German heavy ships, which, according to the reconstruction, were at that time approximately 17 miles away. At 17:18, the submarine commander finally correctly identified the target, estimating the distance to the German heavy ships to be 10–12 miles (14–15 miles according to the reconstruction).