SM U-9

SM U-9 was a German Type U 9 U-boat. She was one of 329 submarines serving in the Imperial German Navy, and engaged in commerce raiding (Handelskrieg) during World War I.

Construction
Her construction was ordered on 15 July 1908 and her keel was laid down by Kaiserliche Werft in Danzig. She was launched on 22 February 1910 and commissioned on 18 April 1910.

Design
U-9 had an overall length of 57.38 m, her pressure hull was 48 m long. The boat's beam was 6 m (o/a), while the pressure hull measured 3.65 m. She had a draught of 3.13 m with a total height of 7.05 m. The boat displaced 493 t when surfaced and 611 t when submerged.

U-9 was fitted with two Körting 8-cylinder plus two Körting 6-cylinder two-stroke petrol engines with a total of 1000 PS for use on the surface and two Siemens-Schuckert double-acting electric motors plus two electric motors with a total of 1160 PS for underwater use. These engines powered two shafts, each with a 1.45 m propeller, which gave the boat a top surface speed of 14.2 kn, and 8.1 kn when submerged. Cruising range was 1800 nmi at 14 kn on the surface, and 80 nmi at 5 kn under water. Diving depth was 50 m.

The U-boat was armed with four 50 cm 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 3.7 cm Hotchkiss gun when war broke out in 1914. In 1915, an additional 5 cm 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, Kapitänleutnant Otto 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 British Cressy-class armoured cruisers (HMS Aboukir (1900), HMS Hogue (1900), and HMS Cressy (1899), sardonically nicknamed the "Live Bait Squadron"), 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.

On 15 October, U-9 sank the protected cruiser HMS Hawke (1891). 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 (Don, Queen Wilhelmina and Serbino).

After April 1916, she was withdrawn from front-line duties to be used for training.

U-9 and the raider SMS Emden (1906) were the only ships which Kaiser Wilhelm II awarded the Iron Cross.