SM U-66

SM U-66

SM U-66 was the lead ship of the Type U 66 submarines or U-boats for the German Imperial Navy (German: Kaiserliche Marine) during the First World War. The submarine had been laid down in November 1913 as U-7, the lead ship 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-7 from Germaniawerft of Kiel as the first 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-7, 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-7 became U-66, and all were redesigned and reconstructed to German specifications. U-66 was launched in April 1915 and commissioned in July. As completed, she displaced 791 metric tons (872 short tons), surfaced, and 933 metric tons (1,028 short tons), submerged. The boat was 228 feet (69 m) long and was armed with five torpedo tubes and a deck gun.

As a part of the Baltic and 4th Flotillas, U-66 sank 24 ships with a combined gross register tonnage of 69,967 in six war patrols. The U-boat also torpedoed and damaged the British cruiser Falmouth in August 1916. U-66 left Emden on her seventh patrol on 2 September 1917 for operations in the North Channel. The following day the U-boat reported her position in the North Sea but neither she nor any of her 40-man crew were ever heard from again. A postwar German study offered no explanation for U-66's loss, although British records suggest that she may have struck a mine in the Dogger Bank area.