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. U-68 was sunk by the British Q-ship in March 1916, and was the first boat of the class to be lost during the war. U-69 and U-66 were lost in July and September 1917, respectively. 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 (). U-67 was surrendered to the United Kingdom on 20 November 1918 and was broken up at Fareham in 1921. SM U-68 U-68 was laid down on 31 December 1913 (yard number 205) by Germaniawerft at Kiel and launched on 1