U-9 had an overall length of, her pressure hull was long. The boat's beam was , while the pressure hull measured. She had a draught of with a total height of. The boat displaced when surfaced and when submerged. U-9 was fitted with two Körting 8-cylinder plus two Körting 6-cylinder two-stroke petrol engines with a total of for use on the surface and two Siemens-Schuckertdouble-acting electric motors plus two electric motors with a total of for underwater use. These engines powered two shafts, each with a propeller, which gave the boat a top surface speed of, and when submerged. Cruising range was at on the surface, and at under water. Diving depth was. The U-boat was armed with four torpedo tubes, two fitted in the bow and two in the stern, and carried 6 torpedoes. Originally, the boat was equipped with a machine gun, which was augmented with a Hotchkiss gun when war broke out in 1914. In 1915, an additional gun was fitted. When U-9 underwent a major refit in 1916, two mine-laying rails were added, which were later removed again. The boat's complement was 4 officers and 31 enlisted.
Service history
On 16 July 1914, the crew of U-9 reloaded her torpedo tubes while submerged, the first time any submarine had succeeded in doing so. On 1 August 1914, KapitänleutnantOtto Weddigen took command. On 22 September, while patrolling the Broad Fourteens, a region of the southern North Sea, U-9 found a squadron of three obsolescent British Cressy-class armoured cruisers, which had been assigned to prevent German surface vessels from entering the eastern end of the English Channel. She fired four of her torpedoes, reloading while submerged, and sank all three in less than an hour. 1,459 British sailors died. It was one of the most notable submarine actions of all time. Members of the Admiralty who had considered submarines mere toys no longer expressed that opinion after this event. depicting the sinking of, and by U-9 on 22 September 1914 off the Dutch coast. On 15 October, U-9 sank the protected cruiser. On 12 January 1915, Johannes Spieß relieved Weddigen, and commanded U-9 until 19 April 1916. During this period, she sank 13 ships totalling : 10 small fishing vessels and three British steamers. After April 1916, she was withdrawn from front-line duties to be used for training. U-9 and the raider were the only ships which Kaiser Wilhelm II awarded the Iron Cross.
