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SM U-70

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German Empire
Name: U-70
Ordered: 2 February 1913
Builder: Germaniawerft, Kiel[1]
Yard number: 207[2]
Laid down: 11 February 1914, as U-11 (Austria-Hungary)[2]
Launched: 20 July 1915[2]
Commissioned: 22 September 1915[2]
Fate: surrendered 20 November 1918; broken up, 1919–20
General characteristics [3]
Class and type: German Type U 66 submarine
  • 791 t (779 long tons) surfaced
  • 933 t (918 long tons) submerged
  • 6.30 m (20 ft 8 in) (o/a)
  • 4.15 m (13 ft 7 in) (pressure hull)
Height: 7.95 m (26 ft 1 in)
Draft: 3.79 m (12 ft 5 in)
  • 16.8 knots (31.1 km/h; 19.3 mph) surfaced
  • 10.3 knots (19.1 km/h; 11.9 mph) submerged
  • 7,370 nmi (13,650 km; 8,480 mi) at 8 knots (15 km/h; 9.2 mph) surfaced
  • 115 nmi (213 km; 132 mi) at 4 knots (7.4 km/h; 4.6 mph) submerged
Test depth: 50 m (160 ft)
Complement: 4 officers, 32 enlisted men
Service record
Part of: IV Flottille (March 1916 – July 1917)[2]
Operations: 12 war patrols[2]
  • 53 ships (137,775 GRT) sunk[2]
  • 4 ships (20,369 GRT) damaged
  • 1 warship (1,290 t displ.) sunk

SM U-70 was a Type U 66 submarine or U-boat for the German Imperial Navy (German: Kaiserliche Marine) during the First World War. She had been laid down in February 1914 as U-11 the final boat of the U-7 class for the Austro-Hungarian Navy (German: Kaiserliche und Königliche Kriegsmarine or K.u.K. Kriegsmarine) but was sold to Germany, along with the others in her class, in November 1914.

The submarine was ordered as U-11 from Germaniawerft of Kiel as the last of five boats of the U-7 class for the Austro-Hungarian Navy. After the outbreak of World War I in August 1914, the Austro-Hungarian Navy became convinced that none of the submarines of the class could be delivered to the Adriatic via Gibraltar. As a consequence, the entire class, including U-11, was sold to the German Imperial Navy in November 1914. Under German control, the class became known as the U 66 type and the boats were renumbered; U-11 became U-70, and all were redesigned and reconstructed to German specifications. U-70 was launched in July 1915 and commissioned in September. As completed, she displaced 791 tonnes (779 long tons), surfaced, and 933 tonnes (918 long tons), submerged. The boat was 69.50 metres (228 ft) long and was armed with five torpedo tubes and a deck gun.

A part of the 4th Flotilla throughout the war, U-70 sank 53 merchant ships with a combined gross register tonnage (GRT) of 137,775. Included in that total was Southland—at 11,899 GRT, one of the largest ships of the war sunk by a U-boat—sunk in June 1917. In addition she sank one British Flower-class sloop and damaged four merchant ships (20,369 GRT). On 20 November 1918, nine days after the Armistice, U-70 was surrendered to the British. She was broken up at Bo'ness in 1919–20.

Design and construction

After the Austro-Hungarian Navy had competitively evaluated three foreign submarine designs, it selected the Germaniawerft 506d design, also known as the Type UD, for its new U-7 class of five submarines.[6] The Navy ordered five boats on 1 February 1913.[7]

The U-7 class was seen by the Austro-Hungarian Navy as an improved version of its U-3 class, which was also a Germaniawerft design.[7][Note 2] As designed for the Austro-Hungarian Navy, the boats were to displace 695 tonnes (684 long tons) on the surface and 885 tonnes (871 long tons) while submerged. The doubled-hulled boats were to be 69.50 metres (228 ft) long overall with a beam of 6.30 metres (20.7 ft) and a draft of 3.79 metres (12.4 ft). The Austrian specifications called for two shafts with twin diesel engines (2,300 metric horsepower (2,269 bhp; 1,692 kW) total) for surface running at up to 17 knots (31 km/h; 20 mph), and twin electric motors (1,240 metric horsepower (1,223 shp; 912 kW) total) for a maximum of 11 knots (20 km/h; 13 mph) when submerged.[7] The boats were designed with five 45 cm (17.7 in) torpedo tubes; four located in the bow, one in the stern. The boats' armament was to also include a single 6.6 cm (2.6 in) deck gun.[7]

U-11 was laid down on 11 February 1914, the final boat of the class begun.[8] Her construction was slated to be complete within 29 to 33 months.[7]

Neither U-11 nor any of her sister boats were complete when World War I began in August 1914.[8] With the boats under construction at Kiel, the Austrians became convinced that it would be impossible to take delivery of the boats, which would need to be towed into the Mediterranean past Gibraltar, a British territory.[7][Note 3] As a result, U-11 and her four sisters were sold to the Imperial German Navy on 28 November 1914.[1][Note 4]

U-11 was renumbered by the Germans as U-70 when her class was redesignated as the Type U 66. The Imperial German Navy had the submarines redesigned and reconstructed to German standards, which increased the surface displacement by 96 tonnes (94 long tons) and the submerged by 48 tonnes (47 long tons). The torpedo load was increased by a third, from 9 to 12, and the deck gun was upgraded from the 6.6 cm (2.6 in) gun originally specified to an 8.8 cm (3.5 in) Uk L/30 one.[1]

Early career

U-70 was launched on 20 July 1915.[1] On 22 September, SM U-70 was commissioned into the German Imperial Navy under the command of Kapitänleutnant Otto Wünsche.[2][Note 5] U-70 was the second U-boat command for the 30-year-old officer; he had commanded U-25 from August 1914 until a week before assignment to U-70.[4] In January 1916, Wünsche and U-70 escorted the German blockade runner Marie through the North Sea.[9] On 9 February, U-70 was assigned to the 4th Flotilla (German: IV. Uhalbflotille) in which she remained for the duration of the war.[10] U-70 served as an escort again in late February, when she accompanied the German merchant raider Greif.[9][Note 6]

The second German offensive

Germany began its second submarine offensive against shipping in February 1916, the month U-70 had joined the 4th Flotilla. As in the first submarine offensive, U-boats were sent independently around Scotland to patrol the Irish Sea and the western entrance to the English Channel.[11] U-70 sank her first ship on 16 March,[12] when she dispatched the British sailing vessel Willie 60 nautical miles (110 km; 69 mi) northwest by west of Fastnet Rock.[13] The same day she also damaged the British cargo ship Berwindale, en route to Avonmouth with a load of wheat from Galveston, Texas.[14] Throughout the rest of March and into early April, U-70 sank an additional five ships of 14,557 gross register tons (GRT);[12] the largest being the British cargo vessel Eagle Point, carrying a load of hay and oats from Saint John, New Brunswick, torpedoed and sunk on 28 March.[15] Near the end of April 1916, Admiral Reinhard Scheer, the new commander-in-chief of the High Seas Fleet (under which U-70's 4th Flotilla operated), called off the merchant shipping offensive and ordered all boats at sea to return, and all boats in port to remain there.[16]

Grand Fleet ambush

In mid-May, Scheer completed plans to draw out part of the British Grand Fleet.[17] The German High Seas Fleet would sortie for a raid on Sunderland,[18] luring the British fleet across "'nests' of submarines and mine-fields".[17] U-70 was one of four U-boats that put out to sea beginning on 18 May to scout the central North Sea for signs of the British fleet. Completing five days of scouting, U-70, along with U-63, U-51, U-32, sister boat U-66, U-24, and U-52, took up position off the Firth of Forth on 23 May. The other two other boats, U-43 and U-44, were stationed off Pentland Firth, in position to attack the British fleet leaving Scapa Flow. All the boats were to remain on station until 1 June and await a coded message which would report the sailing of the British fleet.[18] Unfortunately for the Germans, the British Admiralty had intelligence reports of the departure of the submarines which, coupled with an absence of attacks on shipping, aroused British suspicions.[17]

A delayed departure of the German fleet for its sortie (which had been redirected to the Skagerrak) and the failure of five U-boats to receive the coded message warning of the British advance caused Scheer's anticipated ambush to be a "complete and disappointing failure".[19] Although U-70 had received the advance warning of the coded message, her crew did not ever see any part of the fleet.[Note 7] The failure of the submarine ambush to sink any British capital ships allowed the full Grand Fleet to engage the numerically inferior High Seas Fleet in the Battle of Jutland, which took place 31 May – 1 June.[20]

U-70's next success came in December when she sank the 5,587-ton British steamer Pascal on 17 December. Over the next month she sank an additional 15 ships (20,545 GRT).[12]

Unrestricted submarine warfare

From the early stages of the war the British had blockaded Germany, preventing neutral shipping from reaching German ports. By the time of the so-called "turnip winter" of 1916–17, the blockade had severely limited imports of food and fuel into Germany.[21] Among the results were an increase in infant mortality and as many as 700,000 deaths attributed to starvation or hypothermia during the war.[22] With the blockade having such dire consequences, Kaiser Wilhelm II personally approved a resumption of unrestricted submarine warfare to begin on 1 February 1917 to help force the British to make peace.[23] The new rules of engagement specified that no ship was to be left afloat.[24]

The first recorded action of U-70 under the new rules of engagement occurred near the end of February 1917, when the U-boat shelled the British-flagged SS San Patricio. The 9,712 GRT tanker, encountered by U-70 off the Orkney Islands, survived the attack.[25][Note 8] In March, U-70 sank twelve ships totaling 25,708 tons and damaged a thirteenth of 4,666 tons.[12]

During the month of April 1917, German U-boats succeeded in sinking 860,334 tons of Allied and neutral shipping, a total unsurpassed by any month in either of the two world wars.[26] U-70's contribution came in the form of ten ships of 23,530 tons sent to the bottom, four of them on the same day, 24 April.[12]

Although the monthly total of tonnage sunk by all U-boats had peaked in April, the losses were over 600,000 tons in each of May and June. U-70 did not contribute to the May tally but her commanding officer, Wünsche, was awarded the House Order of Hohenzollern.[4] U-70 began another productive month in June by sinking the American Line ocean liner Southland on 4 June. At 11,899 GRT, Southland was the largest ship sunk by U-70,[12] and one of the largest ships sunk during the war by a U-boat.[27] Southland was carrying a general cargo from Liverpool to Philadelphia when U-70 sank her at position 56°10′N 12°14′W / 56.167°N 12.233°W / 56.167; -12.233, some 140 nautical miles (260 km; 160 mi) from Tory Island.[28] Throughout the rest of June, U-70 sank another seven ships totaling 26,131 tons.[12]

After June 1917, U-70 only sank another three ships throughout the rest of the war, one of which was the British Flower-class sloop Rhododendron on 5 May 1918.[12] Rhododendron had been constructed in 1917 as a purpose built Q-ship, a warship disguised as a merchant ship to lure German submarines within range of their concealed gun batteries. The sloop was patrolling off Mull Head in the Orkney Islands when struck by a single torpedo from U-70. The captain, Lieutenant Commander Charles Arthur Peal, became disoriented in the aftermath of the explosion, and instead of ordering away a "panic party" to draw the submarine within range, ordered the complete evacuation of the ship, which was carried out in great haste and confusion. U-70 approached the burning ship and observed the chaotic evacuation, seizing a petty officer from a liferaft who revealed the ship's true identity. U-70 shelled the wreck and escaped without coming under fire. Rhododendron capsized and sank the following morning, with the loss of 15 men, four killed in the explosion and 11 drowned during the evacuation. Peal and the rest of the crew were heavily criticized for their conduct under fire by an Admiralty board.[29]

In total U-70 sank 54 ships with a combined tonnage of 139,065 and damaged four with a tonnage of 20,369 in her twelve war patrols. She was surrendered to the British on 20 November 1918, nine days after the Armistice, and broken up at Bo'ness in 1919–20.[2]

Summary of raiding history

Ships sunk or damaged by SM U-70[12]
Date Name Nationality [Note 9] Tonnage Fate
16 March 1916 Berwindvale  United Kingdom 5,242 Damaged
16 March 1916 Willie  United Kingdom 185 Sunk
17 March 1916 Lindfjeld  Norway 2,230 Sunk
22 March 1916 Bougainville  France 2,248 Sunk
24 March 1916 Fenay Bridge  United Kingdom 3,838 Sunk
28 March 1916 Eagle Point  United Kingdom 5,222 Sunk
2 April 1916 Arena  Norway 1,019 Sunk
17 December 1916 Pascal  United Kingdom 5,587 Sunk
18 December 1916 Eugene Gaston  France 184 Sunk
18 December 1916 Flimston  United Kingdom 5,751 Sunk
18 December 1916 Hirondelle  France 148 Sunk
22 December 1916 Avanti  Kingdom of Italy 1,673 Sunk
22 December 1916 Thyra  Norway 749 Damaged
24 December 1916 Harry W. Adams  United Kingdom 127 Sunk
26 December 1916 Spinaway  United Kingdom 96 Sunk
30 December 1916 Borre  Norway 741 Sunk
30 December 1916 Edda  Norway 1,138 Sunk
1 January 1917 Tsiropinas  Greece 3,015 Sunk
2 January 1917 Aconcagua  France 1,313 Sunk
2 January 1917 Odda  Norway 1,101 Sunk
2 January 1917 San Leandro  Spain 1,616 Sunk
4 January 1917 Ruby  Russian Empire 949 Sunk
9 January 1917 Excellent  United Kingdom 1,944 Sunk
27 February 1917 San Patricio  United Kingdom 9,712 Sunk
3 March 1917 Kincardine  United Kingdom 4,108 Sunk
9 March 1917 Inverlogie  United Kingdom 2,347 Sunk
10 March 1917 Mediterranean  United Kingdom 105 Sunk
10 March 1917 T. Crowley  United Kingdom 97 Sunk
12 March 1917 Winnebago  United Kingdom 4,666 Damaged
13 March 1917 Alma  Russian Empire 335 Sunk
13 March 1917 Elizabeth Eleanor  United Kingdom 169 Sunk
13 March 1917 Pera  Russian Empire 1,737 Sunk
15 March 1917 Balaguier  France 2,293 Sunk
15 March 1917 Circe  France 4,133 Sunk
16 March 1917 Norma Pratt  United Kingdom 4,416 Sunk
16 March 1917 Vigilancia  United States 4,115 Sunk
18 March 1917 Joshua Nicholson  United Kingdom 1,853 Sunk
21 April 1917 Sebek  United Kingdom 4,601 Sunk
24 April 1917 Clan Galbraith  Norway 2,168 Sunk
24 April 1917 Eos  Denmark 179 Sunk
24 April 1917 Valkyrian  Sweden 233 Sunk
24 April 1917 Vestdal  Norway 1,690 Sunk
26 April 1917 Harflete  United Kingdom 4,814 Sunk
27 April 1917 Manchester Citizen  United Kingdom 4,251 Sunk
28 April 1917 Anne Marie  Norway 441 Sunk
29 April 1917 Daleby  United Kingdom 3,628 Sunk
30 April 1917 Delamere  United Kingdom 1,525 Sunk
4 June 1917 Southland  United Kingdom 11,899 Sunk
9 June 1917 Appledore  United Kingdom 3,843 Sunk
9 June 1917 Egyptiana  United Kingdom 3,818 Sunk
9 June 1917 Harbury  United Kingdom 4,572 Sunk
10 June 1917 Galicia  United Kingdom 1,400 Sunk
11 June 1917 City of Perth  United Kingdom 3,427 Sunk
18 June 1917 Queen Adelaide  United Kingdom 4,965 Sunk
19 June 1917 Buffalo  United Kingdom 4,106 Sunk
25 August 1917 Malda  United Kingdom 7,896 Sunk
5 May 1918 HMS Rhododendron  Royal Navy 1,290 Sunk
7 July 1918 Carl  Denmark 2,486 Sunk


  1. ^ On the U 70 page at, Helgason reports that Otto Wünsche was in command only through October 1917, but the listing of ships hit by U-70 from the same website reports that he was still in command as late as July 1918.
  2. ^ The U-3-class submarines, however, were less than half the displacement and nearly 90 feet (27 m) shorter than the U-7 design. See: Gardiner, pp. 342–43.
  3. ^ The Austro-Hungarian Navy's Germaniawerft-built U-3 class boats had been towed from Kiel to Pola via Gibraltar in 1909. See: Sieche, p. 19.
  4. ^ In April 1915, just five months later, the German U-21 successfully entered the Mediterranean through the Straits of Gibraltar, proving that delivery would have been possible after all. See: Gardiner, p. 343.
  5. ^ Wünsche was in the Navy's April 1902 cadet class with 29 other future U-boat captains, including Gustav Sieß, Max Valentiner, and Hans Walther. See: Helgason, Guðmundur. "WWI Officer Crews: Crew 4/02". German and Austrian U-boats of World War I - Kaiserliche Marine - Retrieved 17 February 2009.
  6. ^ SMS Greif (auxiliary cruiser) and British armed merchant cruiser Alcantara met and sank each other on 29 February in the North Sea.
  7. ^ Sister boat U-66 and U-32 were the only two to report British fleet sightings. See: Gibson and Prendergast, p. 99.
  8. ^ Although San Patricio survived two different U-boat attacks in 1917—U-70's gunfire attack on 27 February and a torpedo attack on 8 May by UC-65—she was torpedoed and sunk in March 1943 (as Southern Princess) by U-600 during World War II. See: Helgason, Guðmundur. "Ships hit during WWI: Southern Princess". German and Austrian U-boats of World War I - Kaiserliche Marine - Retrieved 9 December 2008.
  9. ^ Merchant ship tonnages are in gross register tons. Military vessels are listed by tons displacement.


  1. ^ a b c d Gardiner, p. 177.
  2. ^ a b c d e f g h i j Helgason, Guðmundur. "WWI U-boats: U 70". German and Austrian U-boats of World War I - Kaiserliche Marine - Retrieved 9 December 2008.
  3. ^ Gröner 1991, p. 10.
  4. ^ a b c Helgason, Guðmundur. "WWI U-boat commanders: Otto Wünsche". German and Austrian U-boats of World War I - Kaiserliche Marine -
  5. ^ Helgason, Guðmundur. "WWI U-boat commanders: Joachim Born". German and Austrian U-boats of World War I - Kaiserliche Marine -
  6. ^ Gardiner, p. 340.
  7. ^ a b c d e f Gardiner, p. 343.
  8. ^ a b Helgason, Guðmundur. WWI U-boats: U 66, WWI U-boats: U 67, WWI U-boats: U 68, WWI U-boats: U 69, WWI U-boats: U 70. U-Boat War in World War I. Retrieved on 9 December 2008.
  9. ^ a b Gibson and Prendergast, p. 83.
  10. ^ Tarrant, p. 34.
  11. ^ Tarrant, p. 27–28.
  12. ^ a b c d e f g h i Helgason, Guðmundur. "Ships hit by U 70". German and Austrian U-boats of World War I - Kaiserliche Marine - Retrieved 9 December 2008.
  13. ^ Helgason, Guðmundur. "Ships hit during WWI: Willie". German and Austrian U-boats of World War I - Kaiserliche Marine - Retrieved 9 December 2008.
  14. ^ Helgason, Guðmundur. "Ships hit during WWI: Berwindale". German and Austrian U-boats of World War I - Kaiserliche Marine - Retrieved 9 December 2008.
  15. ^ Tennent, p. 97.
  16. ^ Tarrant, p. 30.
  17. ^ a b c Gibson and Prendergast, p. 97.
  18. ^ a b Tarrant, p. 31.
  19. ^ Tarrant, p. 32.
  20. ^ Tarrant, pp. 32–33.
  21. ^ Tarrant, pp. 44–45.
  22. ^ Tarrant, p. 45.
  23. ^ Tarrant, pp. 45–46.
  24. ^ Tarrant, p. 46.
  25. ^ Helgason, Guðmundur. "Ships hit during WWI: San Patricio". German and Austrian U-boats of World War I - Kaiserliche Marine - Retrieved 9 December 2008.
  26. ^ Tarrant, p. 47.
  27. ^ Helgason, Guðmundur. "Ships hit during WWI: Largest Ships sunk or damaged". German and Austrian U-boats of World War I - Kaiserliche Marine - Retrieved 6 December 2008.
  28. ^ Tennent, p. 138
  29. ^ Hepper, p. 131.


  • Gardiner, Robert, ed. (1985). Conway's All the World's Fighting Ships, 1906–1921. Annapolis, Maryland: Naval Institute Press. ISBN 978-0-87021-907-8. OCLC 12119866.CS1 maint: extra text: authors list (link)
  • Gröner, Erich; Jung, Dieter; Maass, Martin (1991). U-boats and Mine Warfare Vessels. German Warships 1815–1945. 2. Translated by Thomas, Keith; Magowan, Rachel. London: Conway Maritime Press. ISBN 0-85177-593-4.
  • Gibson, R. H.; Prendergast, Maurice (2003) [1931]. The German Submarine War, 1914–1918. Annapolis, Maryland: Naval Institute Press. ISBN 978-1-59114-314-7. OCLC 52924732.
  • Hepper, David (2006). British Warship Losses in the Ironclad Era 1860–1919. London: Chatham Publishing. ISBN 978-1-86176-273-3. OCLC 237129318.
  • Sieche, Erwin F. (1980). "Austro-Hungarian Submarines". Warship, Volume 2. Naval Institute Press. ISBN 978-0-87021-976-4. OCLC 233144055.
  • Tarrant, V. E. (1989). The U-Boat Offensive: 1914–1945. Annapolis, Maryland: Naval Institute Press. ISBN 978-0-87021-764-7. OCLC 20338385.
  • Tennent, A. J. (2006) [1990]. British Merchant Ships Sunk by U boats in the 1914–1918 War. Penzance: Periscope Publishing. ISBN 1-904381-36-7.
  • Spindler, Arno (1966) [1932]. Der Handelskrieg mit U-Booten. 5 Vols. Berlin: Mittler & Sohn. Vols. 4+5, dealing with 1917+18, are very hard to find: Guildhall Library, London, has them all, also Vol. 1–3 in an English translation: The submarine war against commerce.
  • Beesly, Patrick (1982). Room 40: British Naval Intelligence 1914–1918. London: H Hamilton. ISBN 978-0-241-10864-2.
  • Halpern, Paul G. (1995). A Naval History of World War I. New York: Routledge. ISBN 978-1-85728-498-0.
  • Roessler, Eberhard (1997). Die Unterseeboote der Kaiserlichen Marine. Bonn: Bernard & Graefe. ISBN 978-3-7637-5963-7.
  • Schroeder, Joachim (2002). Die U-Boote des Kaisers. Bonn: Bernard & Graefe. ISBN 978-3-7637-6235-4.
  • Koerver, Hans Joachim (2008). Room 40: German Naval Warfare 1914–1918. Vol I., The Fleet in Action. Steinbach: LIS Reinisch. ISBN 978-3-902433-76-3.
  • Koerver, Hans Joachim (2009). Room 40: German Naval Warfare 1914–1918. Vol II., The Fleet in Being. Steinbach: LIS Reinisch. ISBN 978-3-902433-77-0.

External links

  • Helgason, Guðmundur. "WWI U-boats: U 70". German and Austrian U-boats of World War I - Kaiserliche Marine -
  • Photos of cruises of German submarine U-54 in 1916–1918.
  • A 44 min. German film from 1917 about a cruise of the German submarine U-35.
  • Room 40: original documents, photos and maps about World War I German submarine warfare and British Room 40 Intelligence from The National Archives, Kew, Richmond, UK.

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