Operation Rheinübung

Operation Rheinübung ("Rhine Exercise") was the sortie into the Atlantic by the new German battleship Bismarck and heavy cruiser Prinz Eugen on 18–27 May 1941, during World War II. This operation to block Allied shipping to England culminated in the sinking of Bismarck.

Background
During both World Wars, the island of Britain was dependent upon huge numbers of merchant ships to bring in food and essential raw materials, and protecting this lifeline was one of the highest priorities for British forces. Likewise, Germany recognised that, if this lifeline could be severed, Britain would be defeated, regardless of any other factor.

Operation Rheinubung was the latest in a series of raids on Allied shipping carried out by surface units of the Kriegsmarine. It was preceded by Operation Berlin, a highly successful sortie by Scharnhorst and Gneisenau which ended in March 1941.

By May 1941, the Kriegsmarine battleships Scharnhorst and Gneisenau were at Brest, on the western coast of France, posing a serious threat to the Atlantic convoys, and were heavily bombed by the RAF. The original plan was to have both ships involved in the operation, but Scharnhorst was undergoing heavy repairs to her engines, and Gneisenau had just suffered a damaging torpedo hit days before which put her out of action for 6 months. This left just two new warships available to the Germans: the battleship Bismarck and the heavy cruiser Prinz Eugen (while the Kriegsmarine had three serviceable light cruisers, none had the endurance necessary for a long Atlantic operation), both initially stationed in the Baltic Sea.

The aim of the operation was for Bismarck and Prinz Eugen to break into the Atlantic and attack Allied shipping. Grand Admiral Erich Raeder's orders to Admiral Günther Lütjens were that "the objective of the Bismarck is not to defeat enemies of equal strength, but to tie them down in a delaying action, while preserving her combat capacity as much as possible, so as to allow Prinz Eugen to get at the merchant ships in the convoy" and "The primary target in this operation is the enemy's merchant shipping; enemy warships will be engaged only when that objective makes it necessary and it can be done without excessive risk."

To support and provide facilities for the capital ships to refuel and rearm, German Naval Command (OKM) established a network of tankers and supply ships in the Rheinubung operational area. Seven tankers and two supply ships were sent as far afield as Labrador in the west and the Cape Verde islands in the south.

Lütjens had requested that Raeder delay Rheinübung long enough either for Scharnhorst to complete repairs to her engines and be made combat worthy and to rendezvous at sea with Bismarck and Prinz Eugen or for Bismarck's sister ship Tirpitz to accompany them. Raeder had refused, as Scharnhorst would not be ready until early July. The crew of the newly completed Tirpitz was not yet fully trained, and over Lütjens's protests Raeder ordered Rheinübung to go ahead. Raeder's principal reason for going ahead with Rheinübung was his knowledge of the upcoming Operation Barbarossa, where the Kriegsmarine was only going to play a small and supporting role, and his desire to score a major success with a battleship before Barbarossa that might impress upon Hitler the need not to cut the budget for capital ships.

To meet the threat from German surface ships, the British had stationed at Scapa Flow the new battleships HMS King George V (41) (sometimes referred to as KGV) and HMS Prince of Wales (PoW) as well as the elderly battlecruiser HMS Hood (51). Elsewhere, at Gibraltar, at Halifax, Nova Scotia and at sea in the Atlantic were the battleships Revenge, Rodney and Ramillies, the battlecruisers Repulse and Renown, and the aircraft carriers HMS Ark Royal and Victorious. Cruisers and air patrols provided the fleet's 'eyes'. At sea, or due to sail shortly, were 11 convoys, including a troop convoy.

OKM did not take into account the Royal Navy's determination to destroy the German surface fleet. To make sure Bismarck was sunk, the Royal Navy would ruthlessly strip other theatres of action. This would include denuding valuable convoys of their escorts. The British would ultimately deploy six battleships, three battlecruisers, two aircraft carriers, 16 cruisers, 33 destroyers and eight submarines, along with patrol aircraft. It would become the largest naval force assigned to a single operation up to that point in the war.

Bismarck sails
The heavy cruiser Prinz Eugen sailed at about 21:00 on 18 May 1941 from Gotenhafen (now Gdynia, Poland), followed at 2:00 am, 19 May, by Bismarck. Both ships proceeded under escort, separately and rendezvoused off Cape Arkona on Rügen Island in the western Baltic. They then proceeded through the Danish Islands into the Kattegat. Entering the Kattegat on 20 May Bismarck and Prinz Eugen sailed north toward the Skagerrak, the straight between Jutland and Southern Norway where they were sighted by the Swedish aircraft-carrying cruiser Gotland on around 1:00 pm. Gotland forwarded the sighting in a routine report.

On 21 May, the Admiralty was alerted by sources in the Swedish government that two large warships had been seen in the Kattegat. The ships entered the North Sea and took a brief refuge in a fjord near Bergen, Norway on 21 May, making a break for the Atlantic shipping lanes on the 22nd. By this time, Hood and Prince of Wales, with escorting destroyers, were en route to the Denmark Strait, where two cruisers, Norfolk and Suffolk were already patrolling. The cruisers Manchester and Birmingham were to guard the waters south-east of Iceland.

Once the departure of the German ships was discovered, Admiral Sir John Tovey, the Commander-in-Chief of the British Home Fleet, sailed with the King George V, Victorious and their escorts to support those already at sea. Repulse joined soon afterwards.

On the evening of 23 May, Suffolk sighted Bismarck and Prinz Eugen in the Denmark Strait, close to the Greenland coast. The Admiralty was alerted and Norfolk and Suffolk, hopelessly outgunned, shadowed the German ships. British naval groups were redirected to either intercept Lutjens' force or to cover the troop convoy.

Battle of the Denmark Strait
Hood and Prince of Wales made contact with the German force early on the morning of 24 May, and the action started at 5:52 am, with the combatants about 25,000 yards apart. Hood suffered an early hit, which started a rapidly spreading fire amidships.

Then, at about 6 am, one or more of Hood's magazines exploded, probably as the result of another shell hit from Bismarck. The explosion broke the great battlecruiser's back, and she sank within minutes. All but three of her 1,417-man crew died.

Prince of Wales continued the action, but suffered badly, receiving multiple hits with 15-inch and 8-inch shells, and experiencing repeated mechanical failures with her main armament. Her commanding officer, Captain Leach, wounded when one of Bismarck's shells struck Prince of Wales' bridge, broke off the action, and the British battleship retreated under cover of a smokescreen.

Bismarck had been hit only two (or perhaps three) times. All of the hits had been inflicted by Prince of Wales' 14-inch guns. One of the hits had penetrated the German battleship's hull near the bow, rupturing her fuel tanks, causing her to leak oil continuously and at a serious rate. This was to be a critical factor as the pursuit continued, forcing Bismarck to make for Brest instead of escaping into the great expanse of the Atlantic. The resulting oil slick also helped the British cruisers to shadow her.

The pursuit
Norfolk and Suffolk and the damaged Prince of Wales continued to shadow the Germans, reporting their position to draw British forces to the scene. In response, it was decided that Prinz Eugen would detach to continue raiding, while Bismarck drew off the pursuit. In conjunction with this, Admiral Dönitz committed the U-boat arm to support Bismarck with all available U-boats in the Atlantic. He organized two patrol lines to trap the Home Fleet should Bismarck lead her pursuers to them. One line of 7 boats was arrayed in mid-Atlantic while another, of 8 boats, was stationed west of Biscay. At 6:40 pm on 24 May, Bismarck turned on her pursuers to cover the escape of Prinz Eugen. The German cruiser slipped away undamaged.

At 10 pm, Victorious was 120 miles away and launched an air attack with nine Fairey Swordfish torpedo bombers, which were guided in by Norfolk. In poor weather, and against heavy fire, they attacked and made a single torpedo hit under the bridge. However, up against strong belt armour and torpedo bulges, they failed to cause substantial damage. The attacking aircraft were all safely recovered by Victorious, despite poor weather, darkness, aircrew inexperience and the failure of the carrier's homing beacon.

At 3 am on 25 May, the British shadowers lost contact with Bismarck. At first, it was thought that she would return to the North Sea, and ships were directed accordingly. By the time it was realised that she was heading for Brest, Bismarck had broken the naval cordon and gained a lead. By 11 pm she was well to the east of Tovey's force and had managed to evade Rodney. Bismarck was short of fuel, due to the damaging hit inflicted by Prince of Wales, but was able to outrun the British Home Fleet. From the south, however, Somerville's Force H with the carrier Ark Royal, the battlecruiser Renown, and the light cruiser HMS Sheffield (C24) were approaching to intercept.

The British ships were also beginning to run low on fuel, and the escape of Bismarck seemed more and more certain. However, at 10:30 am, on 26 May, a Catalina flying-boat, based at Lough Erne, Northern Ireland, found Bismarck. She was 700 miles from Brest and not within range of Luftwaffe air cover.

This contact was taken over by two Swordfish from Ark Royal. This carrier now launched an air strike, but her aircrew were unaware of Sheffield's proximity to Bismarck, mistook the British cruiser for the German battleship and therefore immediately attacked her. Their torpedoes had been fitted with influence detonators, and several of them exploded prematurely. Others missed their target, and the attacking aircraft then received a warning from Ark Royal that Sheffield was in the vicinity, whereupon the Swordfish finally recognized the cruiser and broke off the attack.

Ark Royal now launched, in almost impossibly bad weather conditions for air operations, and from a distance of less than 40 miles upwind of Bismarck, a second strike consisting of 15 Swordfish. These were carrying torpedoes equipped with the standard and reliable contact detonators. The attack resulted in two or three hits on the German ship, one of which inflicted critical damage on her steering. A jammed rudder now meant she could now only sail away from her intended destination of Brest. At midnight, Lutjens signalled his headquarters: "Ship unmanoeuvrable. We shall fight to the last shell. Long live the Führer."

Bismarck's end
The battleships Rodney and King George V waited for daylight on 27 May before attacking. At 8:47 am, they opened fire, quickly hitting Bismarck. Her gunners achieved near misses on Rodney, but the British ships had silenced most of the German guns within half an hour. Despite close-range shelling by Rodney, a list to port and widespread fires, Bismarck did not sink.

According to Ballard's underwater surveys in recent years the British guns achieved only four penetrations of Bismarck's armour, two through the upper armour belt on the starboard side from King George V and two on the port side from Rodney. These four hits occurred at about 10:00 am, at close range, causing heavy casualties among the sheltering crew.

Nearly out of fuel – and mindful of possible U-boat attacks – the British battleships left for home. The heavy cruiser HMS Dorsetshire (40) attacked with torpedoes and made three hits. Scuttling charges were soon set off by German sailors, and at 10:40 am, Bismarck capsized and sank. Dorsetshire and the destroyer HMS Maori rescued 110 survivors. After an hour, rescue work was abruptly ended when there were reports of a U-boat presence. Another five survivors were picked up by U-74 and the German weather ship Sachsenwald. Over 2,000 died.

Aftermath
After separating from Bismarck, Prinz Eugen went further south into the Atlantic, intending to continue the commerce raiding mission. On 26 May, with just 160 tons of fuel left, she rendezvoused with the tanker Spichern and refuelled. On 27 May she developed engine trouble, which worsened over the next few days. After a further refuelling on 28 May from Esso Hamburg, Prinz Eugen abandoned her mission on 29 May and headed for Brest. With her speed reduced to 28 knots it was no longer considered practicable to continue. She abandoned her commerce raiding mission without sinking any merchant ships, and made her way to Brest, arriving on 1 June.

In the action, just two U-boats had sighted the British forces, and neither was able to attack. In the aftermath, the British ships were able to evade the patrol lines as they returned to base; there were no further U-boat contacts.

The Luftwaffe also organized sorties against the Home Fleet, but none were successful until 28 May, when planes from Kg77 attacked and sank destroyer Mashona.

After Rheinubung the Royal Navy made a concerted effort to round up the network of supply ships deployed to refuel and rearm the Rheinubung ships. The first success came on 3 June, when the tanker Belchen was discovered by cruisers Aurora and Kenya south of Greenland.

On 4 June tanker Gedania was found in mid-Atlantic by Marsdale, while 100 miles east supply ship Gonzenheim was caught by Esperance Bay, and aircraft from Victorious.

On the same day in the south Atlantic, midway between Belém and Freetown, the southern most limit of the Rheinubung operation, tanker Esso Hamburg was intercepted by cruiser London; while the following day London, accompanied by Brilliant, sank the tanker Egerland.

A week later, on 12 June, tanker Friederich Breme was sunk by cruiser Sheffield in mid-Atlantic. On 15 June, tanker Lothringen was sunk by cruiser Dunedin, with aircraft from Eagle.

In just over two weeks 7 of the 9 supply ships assigned to Operation Rheinubung had been accounted for, with serious consequences for future German surface operations.

Conclusion
Operation Rheinubung was a failure, and although the Germans scored an incidental success by sinking the old battlecruiser Hood, this was more than offset with the loss of the modern battleship Bismarck, which represented one-quarter of the Kriegsmarine's capital ships. No merchant ships were sunk or even sighted by the German heavy surface units during the 2-week raid. Allied convoys were not seriously disrupted; most convoys sailed according to schedule, and there was no diminution of supplies to Britain. On the other hand, the Atlantic U-boat campaign was disrupted; boats in the Atlantic sank just 2 ships in the last weeks of May, compared to 29 at the beginning of the month. As a result of Bismarck's sinking, Hitler forbade any further Atlantic sorties, and her sister ship Tirpitz was sent to Norway. The Kriegsmarine was never again able to mount a major surface operation against Allied supply routes in the North Atlantic; henceforth its only weapon was the U-boat campaign.