On 13 October the German Navy, after receiving intelligence that the British Grand Fleet was at least partly operating from Scapa Flow, sent two U-boats to patrol off the Orkneys. The U9, commanded by Kapitänleutnant Otto Weddigen, which had already sunk three British cruisers in a single engagement, was to patrol to the east of the Orkneys. The U18 was ordered to patrol to the west, but had to return to base almost immediately because of a hot bearing. She was replaced with the U17. The U-boats were to stay 60-100 miles off the Orkneys.
U9 was an early German submarine, carrying only four 17.7 inch torpedo tubes and just six torpedoes. She was capable of only 8 knots submerged. On the surface her Körting paraffin engines gave off a lot of smoke and sparks and a speed of only 14 knots. She could make 8 knots submerged. U17 and U18 were newer, larger and faster: 15 knots on the surface and 9 submerged. However, they had the same armament as U9 and also had paraffin engines.
Other U-boats had been operating in the North Sea; U16 fired two torpedoes at the cruiser HMS Antrim on 9 October, but they missed thanks to orders given quickly by Commander John Webster, Antrim’s navigating officer. He was promoted to Captain for his action.
The Grand Fleet had been patrolling the North Sea in early October because of the risk that German battlecruisers would try and break out in order to attack a convoy that had left Canada on 2 October carrying over 30,000 men and their equipment to Europe. Click here for more details.
It was escorted by four old cruisers, two pre-dreadnought battleships and one of the Royal Navy’s newest battlecruisers, HMS Princess Royal. Other cruisers covered ports on the east coast of the USA in case German liners that had been trapped there by the outbreak of war had been secretly armed and tried to break out to attack the convoy.
So secret was the assignment of Princess Royal to the escort that neither the Canadian government nor the escort commander, Rear Admiral Wester Wemyss, knew about it until she met the convoy in the Atlantic. This level of secrecy was justified by the need to minimise ‘the risk entailed in weakening the 1st Battle Cruiser Squadron.’ The convoy reached the UK without being attacked, although the presence of U-boats in the channel forced it to dock at Devonport rather than Southampton, as originally planned.
On 15 October five Edgar class cruisers were on patrol off Peterhead on the north east coast of Scotland, sailing in line abreast 10 miles apart. Rear Admiral Dudley de Chair’s flagship HMS Crescent had returned to Cromarty to take on coal, ‘but he had left definite instructions for the method of cruising so as to minimise the risk of submarine attack.’
The squadron did not repeat the errors of U9‘s earlier victims, which had kept to a steady course, formation and speed. Instead, the Edgars ‘kept well apart; they continually altered course; they varied their speed.’
However at 9:30 am HMS Hawke and Endymion ‘incredibly’ stopped so that Hawke could send a boat to her sister ship in order to collect mail. Endymion returned to her station once the boat had left. Hawke was stationary for 15 minutes until she had recovered her boat before moving off at 12-13 knots. By then the rest of the squadron was out of sight.
Weddigen had been tracking the squadron since daybreak, but had been unable to get into a position to fire. He dived after almost being run down by a cruiser and came up to periscope depth expecting to have a shot at the cruiser with one of his stern tubes. However, she was in front of U9, so he fired a bow tube. Hawke was hit amidships at 10:30 am and sank within 10 minutes. Only two boats could be launched in the time available.
The rest of the squadron did not know what had happened until 1:20 pm, when U17 fired a torpedo at HMS Theseus. The squadron was obeying de Chair’s instructions regarding anti-submarine measures, and the torpedo missed. The squadron was ordered to head north west at full speed, but Hawke did not reply.
One of Hawke’s boats, with 49 survivors, was found by the Norwegian merchantman Modesta, but there was no sign of the other one, which was probably crushed by Hawke as she capsized. Another 22 men on a raft were rescued by the fast flotilla leader HMS Swift. U17 fired a torpedo at her as she headed to Scapa, but it missed thanks to Swift’s high speed. One of the men rescued died the next day, making a total of 70 saved and 524 lost. They are listed on the website Naval-History.net.
At 1:15 pm on 16 October, the Acorn class destroyers HMS Lyra, Nymphe, Nemesis and Alarm, were making 13 knots on patrol off the eastern entrance to Scapa Flow. Nymphe had just increased speed to 15 knots and followed a change of course signalled by Lyra when her officer of the watch spotted a periscope.
It belonged to U9, which was manoeuvring with the intention of getting between Lyra and Nymphe so that it could torpedo them simultaneously using a stern and a bow tube respectively. It fired a bow torpedo that missed Nymphe by two feet, Nemesis by 200 yards and Alarm by 10 yards after she went hard a port to stop the torpedo hitting her stern. Nymphe tried to ram U9, but Weddigen managed to dive his boat in time. The destroyers stayed in the area until dark, but had no means of attacking a submerged submarine.
There had been a number of false sightings of alleged German U-boats in British harbours. One on 1 September led to the First Battle of Scapa Flow, with British ships firing on phantom periscopes. The first ‘periscope’ sighted was probably a seal. 
The Grand Fleet went to sea after this, with all but the 3rd Battle Squadron then being based at Loch Ewe from 5 to 24 September. This base was thought to be far enough from German bases to be safe from U-boats, but it was also too far from the English Channel for the Grand Fleet to have arrived in time had German High Seas Fleet entered the English Channel to attack the British Army’s supply ships.
In October a mistaken sighting of a periscope as the battle cruisers entered the Cromarty Firth led to the Battle of Jemimaville in which a 4 inch shell damaged the roof and chimney of a house in the village of Jemimaville. A baby was slightly injured, but the parents were ‘soothed’ with the news that two U-boats had been sunk.
At 4 pm on the afternoon of 16 October, it was reported wrongly that there was a U-boat in Scapa Flow. Loch Ewe had been abandoned as a base after a U-boat had been reported in the harbour on 6 October. There was another reporting of a submarine in Scapa Flow on 17 October. The next day the Grand Fleet’s commander Admiral Sir John Jellicoe started to move it to Lough Swilly on the north coast of Ireland and Loch na Keal, south of Loch Ewe. These harbours had narrow and easily defensible entrances and Lough Swilly was shallow, making it hard for a submerged submarine to safely enter.
The Grand Fleet returned to Scapa Flow on 9 November. A fortnight later the trawler Dorothy Gray rammed U-18 inside the anchorage. The submarine was so badly damaged that her captain, Kapitänleutnant Heinrich von Henning, had to scuttle her. One man was lost, and the rest of her crew captured. Had she escaped, the Germans would have learnt about the weakness of Scapa Flow’s defences, but her loss made them assume that it was well defended.
There were few more submarine alerts until later in the war. However, it was the middle of 1915 before Scapa Flow had been made secure by the use of sunken merchant ships and booms to block some channels, defensive minefields, seaplanes, gun batteries and searchlights. Hydrophones were later added to the defences.
 Naval Staff Monograph (Historical) 1924 xi, Home Waters part ii, September and October 1914. p. 103.
 J. S. Corbett, H. Newbolt, Naval Operations, 5 vols. (London: HMSO, 1938). i, p. 207
 R. H. Gibson, M. Prendergast, The German Submarine War, 1914-1918. (London: Constable, 1931), p. 12.
 J. Goldrick, The King’s Ships Were at Sea: The War in the North Sea, August 1914-February 1915 (Annapolis, MD: Naval Institute Press, 1984), p. 138.
 A. J. Marder, From the Dreadnought to Scapa Flow; the Royal Navy in the Fisher Era, 1904-1919, 5 vols. (London: Oxford University Press, 1961-70). ii, p. 66.
 R. K. Massie, Castles of Steel: Britain, Germany, and the Winning of the Great War at Sea (London: Jonathan Cape, 2004), p. 155.