Type U 66 submarine

In 1904, the Austro-Hungarian Navy, after allowing the navies of other countries to pioneer submarine developments, ordered the Austrian Naval Technical Committee ( or ) to produce a submarine design. When the Navy rejected the January 1905 MTK design and other designs submitted as part of a public competition as impracticable, they instead opted to order two submarines each of designs by Simon Lake, Germaniawerft, and John Philip Holland for a competitive evaluation. Based on the trials results, the Austro-Hungarian Navy determined the characteristics that the next generation of Austro-Hungarian submarines should have. They were looking for a double-hulled submarine of about displacement with diesel propulsion. They also wanted a surface speed of , and for the boat to be armed with between three and five torpedo tubes. The Austro-Hungarian Navy selected the Germaniawerft 506d design, also known as the Type UD, for the U-7 class over the Type 48 design submitted by Whitehead & Co., primarily because of the lower cost. The Navy ordered five boats on 1 February 1913. == Design ==

The U-7 class was seen by the Austro-Hungarian Navy as an improved version of its , which was also a Germaniawerft design. As designed for the Austro-Hungarian Navy, the boats were to displace on the surface and while submerged. The doubled-hulled boats were to be long overall with a beam of and a draft of . The Austrian specifications called for two shafts with twin diesel engines ( total) for surface running at up to , and twin electric motors ( total) for a maximum of when submerged. The boats were designed with five torpedo tubes; four located in the bow, one in the stern. The boats' armament was to also include a single /26 deck gun. == Construction ==

After the Austro-Hungarian Navy's 1 February 1913 order, the first two boats, U-7 and U-8, were laid down at Germaniawerft on 1 November. U-9 was laid down at the end of December, and the final two boats, U-10 and U-11 were both begun in February 1914. Construction of the boats was slated to be complete within 29 to 33 months. None of the submarines were complete when World War I began in August 1914. As a result, the five boats of the class were transferred to the Imperial German Navy on 28 November 1914 after the advance payment of 2 million Kronen had been returned. Germaniawerft was then awarded Kriegsauftrag D, hence the type was known as UD. After their purchase, the boats were assigned the numbers U-66 to U-70, and the class became known as the U 66 type. The Imperial German Navy had the submarines redesigned and reconstructed to German standards, which increased the surface displacement by and the submerged by . The torpedo load was increased by a third, from 9 to 12, and the deck gun was upgraded from the gun originally specified to an SK L/30 one. U-66 was launched on 22 April 1915, the first of the class, and was followed by the other four about one every three weeks, with the last boat, U-70, hitting the water on 20 July. The boats were all completed and commissioned into the Imperial German Navy between July and September. == Service career ==

All the boats of the U-66 class saw active service, and all but one boat, , had wartime successes; and both sank over 100,000 GRT of Allied shipping. and U-70 both survived the war and were surrendered to the United Kingdom in November 1918, and both were broken up by 1921. == Boats in class ==

SM U-66 U-66, the lead boat of the class, was laid down on 1 November 1913 (yard number 203) by Germaniawerft at Kiel and launched on 22 April 1915. She was commissioned on 23 July 1915 under the command of Kapitänleutnant Thorwald von Bothmer. During the war, she sank 25 ships totaling . The two largest ships she sank were the British steamers Powhatan () and Bay State (), both sunk in 1917. U-66 was last heard from on 3 September 1917 when she reported her position in the North Sea. Her fate is officially unknown. British records suggest that U-66 may have struck a mine or been sunk by destroyers, this is not borne out by German records. SM U-67 U-67 was laid down on 1 November 1913 (yard number 204) by Germaniawerft at Kiel and launched on 15 May 1915. She was commissioned on 4 August 1915 under the command of Korvettenkapitän Erich von Rosenberg-Grusczyski. U-67 sank a total of 17 ships () and damaged a further four (). Six days into her first war patrol, U-68 encountered the British Q-ship (Q-ship number five) off Dingle and was sunk with all hands. U-68 sank no ships during her brief service career. SM U-69 U-69 was laid down on 7 February 1914 (yard number 206) by Germaniawerft at Kiel and launched on 24 June 1915. She was commissioned on 4 September 1915 under the command of Kapitänleutnant Ernst Wilhelms. During her service career, U-69 sank 31 ships with a combined gross register tonnage of 102,875, the largest among them, the 13,441 GRT armed merchant cruiser . U-69 was last heard from on 11 July 1917 when she reported being off the coast of Norway. Her fate is officially unknown, even though British reports credit her sinking to destroyer . The dates in German records, however, do not support this claim. SM U-70 U-70 was laid down on 11 February 1914 (yard number 207) by Germaniawerft at Kiel and launched on 20 July 1915. She was commissioned on 22 September 1915 under the command of Kapitänleutnant Otto Wünsche. During the war, Wünsche and U-70 sank one warship, the British sloop , and 53 civilian ships totaling . Among the civilian ships was , U-70 also damaged five ships of . U-70 was surrendered to the British on 20 November 1918 and was broken up at Bo'ness in 1919–20. == Notes ==