On 5 September 1914 the German U-boat U21 sank the British cruiser HMS Pathfinder. Eight days later the British submarine E9 sank the German light cruiser SMS Hela.
Britain’s submarines were commanded by the aggressive Commodore Roger Keyes. His main striking force consisted of the eight D class and 10 E class boats of the Eighth Submarine Flotilla. The older A, B and C class submarines were small and short ranged, so were suitable only for coastal defence.
Keyes’s submarines made repeated patrols into German waters, where they saw few potential targets. He wrote in his memoirs that the conditions for the crews were very tough:
‘the notoriously short, steep seas which accompany westerly gales in the Helgoland Bight…make it difficult to open the conning tower hatches and vision is limited to about 200 yards. There was no rest to be obtained on the bottom…even when cruising at a depth of sixty feet, the submarines were rolling and moving vertically twenty feet.’
At dawn on 6 September E9, captained by Lieutenant-Commander Max Horton, surfaced after spending the previous night on the bottom of the sea 120 feet below the surface, six miles south-south-west of Helgoland.
E-9 immediately spotted the old German light cruiser SMS Hela less than two miles away and manoeuvred to attack. She fired two torpedoes and heard one explosion as she dived. Horton brought his boat back up and saw that Hela had stopped and was listing to starboard, but was then forced to dive again by gunfire. An hour later E9 surfaced and found only four or five trawlers where the cruiser had been. Most of Hela’s crew had been rescued.
Horton was awarded the Distinguished Service Order for this and the sinking of the destroyer SMS S116 off the River Ems on 6 October. He rose to the rank of Admiral and was Commander-in-Chief of the Western Approaches in the Second World War, where he proved to be as skilful at fighting submarines as he had been at commanding one.
 Quoted in R. K. Massie, Castles of Steel: Britain, Germany, and the Winning of the Great War at Sea (London: Jonathan Cape, 2004), p. 125.