U-47: The U-Boat That Struck Scapa Flow

U-47 was a German Type VIIB U-boat of the Second World War, famous for one of the most daring operations in submarine history: the sinking of the British battleship HMS Royal Oak at her anchorage in Scapa Flow on the night of 14 October 1939. Under the command of Gunther Prien, U-47 slipped through the defences of the Royal Navy’s main base in the Orkney Islands, torpedoed the battleship at anchor, and escaped, killing 835 men, including the battleship’s captain and more than a hundred boy sailors. The raid was a propaganda triumph for Germany and a shock for Britain, and it made Prien a national hero. U-47 went on to carry out ten war patrols, sinking 30 merchant ships and the battleship Royal Oak, before it was lost with all hands in March 1941, in circumstances that remain uncertain to this day.

U-47’s story is the story of the early U-boat war, when a handful of submarines, operating from German bases, could strike at the heart of British sea power. The boat was a Type VIIB, a medium-sized ocean-going submarine that was the standard type in 1939, and its career followed the pattern of the U-boat arm’s early successes: aggressive patrols, heavy sinkings and growing fame, followed by increasing danger as British defences improved. U-47’s loss in March 1941, on its tenth patrol, was one of the first signs that the U-boat war was changing, and that the days of easy success were coming to an end.

Today U-47 is remembered above all for the Scapa Flow raid, which remains one of the most famous submarine operations in history. The wreck of the Royal Oak still lies in Scapa Flow, a war grave that is visited by divers and remembered by the people of Orkney, and the story of U-47 and its commander continues to be told in books and documentaries. The boat’s fate, lost with all 45 of its crew, is a reminder of the human cost of the U-boat war, in which more than 30,000 German submariners died, three quarters of all who served.

1. Key Facts

Field	Value
Type	Type VIIB U-boat
Origin	Germany
Builder	Germaniawerft, Kiel
Laid down	25 February 1937
Launched	29 October 1938
Commissioned	17 December 1938
Displacement	753 tons surfaced; 857 tons submerged
Length	Approximately 66.50 m (218 ft 2 in)
Beam	Approximately 6.20 m (20 ft 4 in)
Draught	Approximately 4.74 m (15 ft 7 in)
Propulsion	2 × MAN M6V diesel engines, 2,800–3,200 hp surfaced; 2 × electric motors, 750 hp submerged
Speed	17.9 knots surfaced; 8 knots submerged
Range	Approximately 8,700 nautical miles at 10 knots surfaced
Test depth	220 m (720 ft)
Complement	4 officers, 41 men
Armament	5 × 53.3 cm torpedo tubes (4 bow, 1 stern); 14 torpedoes; 1 × 8.8 cm deck gun; 1 × 2 cm anti-aircraft gun
War patrols	10
Ships sunk	30 merchant ships (about 162,769 GRT) and 1 battleship (HMS Royal Oak, 29,150 tons)
Commander	Gunther Prien (1938–1941)
Fate	Lost with all hands, 7 March 1941, south of Iceland; cause unknown

2. Background and Development

The Type VIIB: Germany’s Ocean-Going Submarine

The Type VIIB was an improved version of the Type VIIA, the first ocean-going submarine built for the Kriegsmarine under the Anglo-German Naval Agreement of 1935. The VIIB was longer than the VIIA, with additional fuel tanks that increased its range to about 8,700 nautical miles, and it carried more torpedoes, with 14 in total. A total of 24 Type VIIB boats were built, and they formed the core of the U-boat arm at the outbreak of war in September 1939. The Type VIIB was a well-balanced boat, fast enough on the surface to keep up with a convoy, well armed and capable of diving quickly, and it set the pattern for the Type VIIC, which became the standard U-boat of the war.

The Type VIIB’s design reflected the lessons of the First World War, when German U-boats had come close to starving Britain into submission, and the ambitions of Admiral Karl Donitz, who believed that a large force of ocean-going U-boats could do the same in a new war. Donitz wanted 300 U-boats, but when war broke out in 1939, Germany had only 57, of which fewer than half were ocean-going types. U-47 was one of the few boats available, and its early successes reflected the skill of its commander and the weakness of British defences in the first months of the war.

Construction and Commissioning

U-47 was laid down at the Germaniawerft yard in Kiel on 25 February 1937, launched on 29 October 1938 and commissioned on 17 December 1938 under the command of Gunther Prien, a 30-year-old officer who had served in the merchant navy before joining the Kriegsmarine and who had already commanded a U-boat. Prien was an aggressive and confident commander, and he quickly established a reputation as one of the U-boat arm’s rising stars. The boat’s emblem, painted on its conning tower, was a snorting bull, a reference to a German newspaper cartoon that had mocked Prien, and it became one of the most famous U-boat emblems of the war, adopted by the whole of the 7th U-boat Flotilla.

U-47 carried out its working-up trials in the Baltic in the first half of 1939, and it was ready for war when Germany invaded Poland on 1 September 1939. The boat’s first patrol, in September 1939, was uneventful, but its second patrol, in October 1939, would make it famous. The Scapa Flow raid was planned by Donitz himself, who had studied the defences of the British base and believed that a U-boat could slip through the gaps in the blockships that guarded the entrances to the anchorage. Prien volunteered for the mission, and on the night of 13–14 October 1939, U-47 entered Scapa Flow and changed the course of the U-boat war.

The Road to Scapa Flow

The decision to attack Scapa Flow was a bold one. The Royal Navy’s main base in the Orkneys was heavily defended, with blockships sunk in the entrances, anti-submarine nets, patrol boats and shore batteries, and a U-boat that entered the anchorage risked being trapped and destroyed. Donitz believed, however, that the defences had gaps, and that a skilled commander could find a way in. Aerial reconnaissance showed that the eastern entrance, Kirk Sound, was blocked by three blockships, but that there were gaps between them through which a U-boat could pass at high water. Prien was chosen for the mission because of his skill and his nerve, and he was given detailed charts and photographs of the anchorage. The raid was a gamble, but it was a gamble that Donitz was willing to take.

3. Design

Hull, Diving and Endurance

The Type VIIB’s hull was a double hull, with an outer casing and an inner pressure hull, divided into compartments by watertight bulkheads. The boat was about 66.5 metres long and 6.2 metres wide, with a crew of 45 men living and working in cramped conditions. The control room, in the centre of the boat, housed the diving planes, the periscopes and the torpedo firing controls, while the forward torpedo room doubled as sleeping quarters. The boat could dive to a test depth of 220 metres, and it could remain submerged for about 24 hours at slow speed, limited by its batteries and by the air supply. Life aboard a Type VIIB was hard, with damp, cold and cramped conditions, but the boat’s crew were volunteers, and they were among the most highly trained men in the German armed forces.

The Type VIIB’s diving time was about 30 seconds from the surface to periscope depth, a crucial quality in a boat that spent most of its time on the surface and needed to dive quickly when threatened. The boat’s trim and handling were good, and Prien and his crew learned to handle U-47 with skill, a quality that was essential in the narrow waters of Scapa Flow, where the boat had to navigate between blockships in the dark, with a strong tidal current running.

Propulsion and Speed

U-47 was powered on the surface by two MAN M6V diesel engines, producing a total of 2,800 to 3,200 horsepower, which gave the boat a surface speed of 17.9 knots. Underwater, the boat was powered by two electric motors producing 750 horsepower, giving a submerged speed of 8 knots, which could be sustained for only a short time. The boat’s range on the surface was about 8,700 nautical miles at 10 knots, enough to reach the Atlantic and return, and its submerged range was about 90 nautical miles at 4 knots. The Type VIIB spent most of its time on the surface, diving only to attack or to evade, and its surface speed was its main defence, allowing it to outrun many escorts.

Armament: Torpedoes and Guns

U-47’s main armament was its torpedoes, carried in five tubes, four in the bow and one in the stern, with a total of 14 torpedoes. The torpedoes were the G7a steam torpedo, which ran at up to 40 knots and left a visible wake, and the G7e electric torpedo, which was slower but left no wake. At Scapa Flow, Prien used a mixture of torpedoes, and his first salvo, fired at the Royal Oak, included torpedoes that failed to explode, a common problem with German torpedoes in the early war. The boat also carried an 8.8 cm deck gun for use against unescorted merchant ships, and a 2 cm anti-aircraft gun. The deck gun was used on several of U-47’s patrols to sink merchant ships by gunfire, saving torpedoes for more important targets.

4. Variants

The Type VII Family

The Type VIIB was one of a family of boats that included the Type VIIA, the Type VIIC and the Type VIID. The VIIA was the first version, built in 1935 and 1936, with a shorter range and fewer torpedoes. The VIIB, with its longer hull and greater range, was the improved version, built from 1936 onwards. The VIIC, which followed in 1940, was a further development of the VIIB, with a slightly larger hull and improved equipment, and it became the standard U-boat of the war, with 568 boats built. The VIID was a minelaying version, with five vertical mine shafts. U-47, as a VIIB, was an early example of the type, and its design was the basis for the boats that followed.

U-47’s Own Modifications

U-47 was not significantly modified during its career, although it received the usual updates to its equipment, including improved torpedoes and a better anti-aircraft gun. The boat’s conning tower carried the snorting bull emblem throughout its service, and the emblem was adopted by the 7th U-boat Flotilla, whose boats all carried the bull. The boat’s torpedo armament and its deck gun remained unchanged, and its crew learned to use them with skill. U-47’s career was short, lasting only two years, and the boat was lost before the major modifications of the later war, such as the snorkel and the radar warning receiver, were introduced.

5. Operational History

The Scapa Flow Raid

The Scapa Flow raid, on the night of 13–14 October 1939, was U-47’s most famous operation. Prien entered the anchorage through Kirk Sound, navigating between the blockships in the dark and on a rising tide, and at 00:58 on 14 October he fired a salvo of torpedoes at the battleship Royal Oak, which was lying at anchor. One torpedo hit the bow, but the explosion was mistaken by the battleship’s crew for an internal explosion, and no alarm was raised. Prien reloaded and fired a second salvo, which hit the Royal Oak amidships, detonating her magazine and causing the battleship to capsize and sink within 15 minutes. A total of 835 men were killed, including the battleship’s captain and more than a hundred boy sailors. Prien escaped from Scapa Flow, navigating back through Kirk Sound, and returned to Germany to a hero’s welcome, where he was awarded the Knight’s Cross by Hitler himself.

The raid was a shock for Britain and a triumph for Germany. The Royal Navy’s main base had been penetrated, and a capital ship had been sunk at anchor. The raid exposed the weaknesses of Scapa Flow’s defences, and the base was evacuated until its defences could be improved. The raid also made Prien a national hero in Germany, and his account of the operation, published as a book, became a bestseller. The raid’s significance was more psychological than material: the Royal Oak was an old battleship, and her loss did not affect the balance of naval power, but the raid demonstrated that the U-boat arm could strike anywhere, and it boosted German morale in the first months of the war.

The Later Patrols

After Scapa Flow, U-47 carried out eight more war patrols, sinking 30 merchant ships and damaging several more. The boat’s patrols took it to the Atlantic, where it attacked convoys and single ships, and to the waters around Britain, where it sank merchantmen and tankers. Prien’s tactics were aggressive: he attacked on the surface at night, using the darkness to approach his targets, and he was willing to press home attacks against escorted convoys. The boat’s successes made Prien one of the most successful U-boat commanders of the early war, and he was awarded the Oak Leaves to his Knight’s Cross in 1940. The boat’s later patrols, however, took place in increasingly difficult conditions, as British escorts, aircraft and technology improved, and the U-boat arm’s losses began to mount.

The Loss of U-47

U-47’s tenth patrol began on 20 February 1941, when the boat sailed from Lorient in France to operate in the Atlantic south of Iceland. On 7 March 1941, the boat attacked a convoy, OB 293, and was reported to have sunk a ship, but it was then lost with all hands. The exact cause of U-47’s loss is unknown. The British destroyer HMS Wolverine claimed to have sunk a U-boat in the area on 7 March, and for many years it was believed that Wolverine had sunk U-47. Later research, however, has cast doubt on this, and it is now thought that U-47 may have been sunk by its own torpedo, which circled back and hit the boat, or by a mine. The wreck of U-47 has never been found, and the fate of Prien and his 44 crewmen remains one of the mysteries of the U-boat war.

The Royal Oak as a War Grave

The wreck of HMS Royal Oak still lies in Scapa Flow, in about 30 metres of water, and it is a designated war grave. The wreck is visited by divers, and a memorial to the 835 men who died is maintained on the island of Hoy. The Royal Oak’s loss is remembered every year on 14 October, when a service is held in Orkney, and the wreck’s oil, which still leaks slowly from the hull, is monitored by the authorities. The Royal Oak’s story is part of the history of Scapa Flow, and U-47’s raid is part of the history of Orkney, where the memory of that October night is still alive.

6. Performance and Specifications

Strengths in Combat

U-47’s strengths were those of the Type VIIB class and of its commander. The boat was fast on the surface, well armed and capable of diving quickly, and Prien was an aggressive and skilful commander who was willing to take risks. The Scapa Flow raid demonstrated the boat’s ability to operate in confined waters and to attack a heavily defended target, and the boat’s later patrols showed its effectiveness against merchant shipping. U-47’s record of 30 merchant ships sunk, together with a battleship, places it among the most successful U-boats of the early war, and its fame rests on the daring of its most famous operation.

Weaknesses and Limitations

The Type VIIB’s weaknesses were those that afflicted the whole U-boat arm: it was slow underwater, its endurance was limited, and it was vulnerable to aircraft and to the improving Allied escort forces. By 1941, the Type VIIB was being replaced by the Type VIIC, and the U-boat arm’s tactics were changing, with the introduction of the wolfpack and the need to operate in groups. U-47’s loss in March 1941, in circumstances that remain uncertain, was a reminder of the dangers of the U-boat war, in which a boat could be lost without a trace, and its crew with it. The U-boat war was a war of attrition, and U-47’s loss was one of many.

7. Comparison

U-47 and Other Famous U-Boats

U-47’s record compares with that of other famous U-boats, such as U-99, commanded by Otto Kretschmer, which sank 35 ships, and U-100, commanded by Joachim Schepke, which sank 25 ships. U-47’s total of 30 merchant ships, plus the Royal Oak, places it among the most successful boats of the early war, although its score was surpassed by later boats, such as U-48, which sank 51 ships. U-47’s fame, however, rests not on its score but on the Scapa Flow raid, which was a unique operation that no other U-boat attempted. The comparison shows that a single daring operation can make a boat famous, even if its overall record is not the highest.

U-47 and the Type VIIC

The Type VIIB and the Type VIIC were very similar boats, and the VIIC, which followed the VIIB, was essentially an improved VIIB with a slightly larger hull and better equipment. U-47, as a VIIB, was an early example of the type, and its design was the basis for the VIIC, which became the standard U-boat of the war. The two types were so similar that their crews could move between them with little retraining, and their tactics and their strengths and weaknesses were the same. U-47’s career illustrates the Type VII design at its best, in the early war when the U-boats were at their most effective.

8. Legacy

The Scapa Flow Raid in Memory

The Scapa Flow raid remains one of the most famous submarine operations in history, and it is remembered in Orkney, in Germany and around the world. The raid’s story has been told in books, films and documentaries, and it continues to fascinate historians and the public. The raid’s significance was psychological: it showed that the Royal Navy’s main base was vulnerable, and it boosted German morale in the first months of the war. The raid’s human cost, 835 men killed, is remembered in Orkney, where the Royal Oak’s loss is still commemorated, and in Germany, where Prien is remembered as a hero, although his reputation has been reassessed in recent years.

Prien and the U-Boat War

Gunther Prien’s reputation has been reassessed since the war. In Germany, he was a national hero, and his book about the Scapa Flow raid was a bestseller. After the war, historians have recognised Prien’s skill as a commander, but they have also noted that his fame was partly a product of Nazi propaganda, and that his later patrols, while successful, were not exceptional. Prien’s loss, with all his crew, in March 1941, was a blow to the U-boat arm, and it marked the end of the early period of the U-boat war, when a handful of commanders dominated the Atlantic. U-47’s legacy is the legacy of the U-boat war itself: daring, skill and courage, and a terrible human cost.

9. Surviving Examples

No Surviving Type VIIB

No Type VIIB U-boat survives, and U-47’s wreck has never been found. The closest surviving example of the Type VII family is U-995, a Type VIIC/41 displayed at Laboe in Germany, which gives visitors an idea of what U-47 looked like and how its crew lived. The Royal Oak’s wreck, in Scapa Flow, is the most tangible reminder of U-47’s most famous operation, and it is a war grave that is protected by law. The absence of a surviving U-47 makes the boat’s story all the more important, since it is preserved in books, in films and in the memories of the people of Orkney.

Memorials in Orkney and Germany

The men of the Royal Oak are commemorated at the Royal Oak memorial on Hoy, in Orkney, and at the Portsmouth Naval Memorial, where the names of the dead are recorded. The men of U-47 are commemorated at the Laboe Naval Memorial in Germany, where the names of the more than 30,000 U-boat men who died in the war are recorded. The two memorials, in Orkney and at Laboe, are reminders of the human cost of the U-boat war, in which both sides lost men in terrible circumstances. U-47’s story is part of that larger story, and it deserves to be remembered.

10. Frequently Asked Questions

How did U-47 sink HMS Royal Oak?
On the night of 13–14 October 1939, U-47 entered Scapa Flow through Kirk Sound, navigating between the blockships, and fired torpedoes at the battleship Royal Oak, which was lying at anchor. A second salvo hit the battleship’s magazine, causing her to capsize and sink within 15 minutes, with the loss of 835 men.

Who commanded U-47?
U-47 was commanded throughout its career by Gunther Prien, who took command when the boat was commissioned in December 1938 and remained in command until the boat was lost in March 1941. Prien became one of Germany’s most famous U-boat commanders.

How many ships did U-47 sink?
U-47 sank 30 merchant ships totalling about 162,769 gross register tons, together with the battleship HMS Royal Oak, and it damaged several more ships.

What happened to U-47?
U-47 was lost with all hands on 7 March 1941, south of Iceland, during its tenth war patrol. The exact cause is unknown: it may have been sunk by the British destroyer HMS Wolverine, by its own torpedo, or by a mine. The wreck has never been found.

What type of submarine was U-47?
U-47 was a German Type VIIB U-boat, the standard ocean-going submarine of the Kriegsmarine at the outbreak of war, and the predecessor of the more numerous Type VIIC.

Can I visit the wreck of HMS Royal Oak?
The wreck of HMS Royal Oak lies in Scapa Flow and is a designated war grave. Diving on the wreck is restricted, but the Royal Oak memorial on Hoy, in Orkney, is open to visitors, and a service is held there every year on 14 October.

11. Sources

• Gunther Prien, Mein Weg nach Scapa Flow (autobiographical account, 1940).
• Clay Blair, Hitler’s U-Boat War: The Hunters 1939–1942 (Random House).
• Jak P. Mallmann Showell, U-Boats at War: Landings on Hostile Shores (Ian Allan).
• The German U-boat Archive, U-47 war diary and patrol records.
• The Royal Oak Association, Scapa Flow memorial records.
• Wikipedia, German submarine U-47 (1938).