On 4 December 1939, Salmon became the first boat to sink a U-boat during the Second World War when it torpedoed and sank the German in the North Sea south-west of Kristiansand, Norway.[1]
The second batch of S-class submarines were designed as slightly improved and enlarged versions of the earlier boats of the class and were intended to operate in the North and Baltic Seas.[2] The submarines had a length of 208feet overall, a beam of 24feet and a mean draught of 11feet. They displaced 768LT on the surface and 960LT submerged.[3] The S-class submarines had a crew of 40 officers and ratings. They had a diving depth of 300feet.[4]
For surface running, the boats were powered by two 7750NaN0 diesel engines, each driving one propeller shaft. When submerged each propeller was driven by a 650hp electric motor. They could reach 13.75kn on the surface and underwater.[5] On the surface, the second-batch boats had a range of 6000nmi at and 64nmi at submerged.[4]
The S-class boats were armed with six 21-inch (533 mm) torpedo tubes in the bow. They carried six reload torpedoes for a total of a dozen torpedoes. They were also armed with a 3-inch (76 mm) deck gun.[3]
Ordered on 20 January 1933, Salmon was laid down on 15 June 1933 in Cammell Laird's shipyard in Birkenhead and was launched on 30 April 1934. The boat was completed on 8 March 1935[6] and received the pennant number 98S.
On 4 December 1939, while on patrol in the North Sea, Salmon torpedoed and sank .[7]
On 12 December 1939, Salmon sighted the German liner . While challenging Bremen, an escorting Dornier Do 18 seaplane forced Salmon to dive. After diving, Salmons commander, Lieutenant Commander E. O. Bickford, decided not to torpedo the liner because he believed she was not a legal target.[8] Bickford's decision not to fire on Bremen likely delayed the start of unrestricted submarine warfare in the war.
On 13 December 1939, Salmon sighted a fleet of German warships. She fired a spread of torpedoes which damaged two German cruisers (one was, the other, her younger sister ship,). Salmon evaded the fleet's destroyers, which hunted her for two hours.
She was lost, probably sunk by a mine, on 9 July 1940.
There is a report from 2008 that the same survey ship that found the wreck of the sister submarine also found the wreck of HMS Salmon nearby in waters off Norway.