There is said to have been an increase in tension in naval circles in the early months of 1916: a sense of calm before the storm. The German Commander-in-Chief, Admiral Hugo von Pohl (an advocate of U-boat warfare against commerce), was known to have been superseded, for reasons of illness, by Vice-Admiral Reinhard Scheer, who was thought likely to use the High Seas Fleet more offensively than his predecessor; and with the Army deadlocked on the Western Front, it was possible that the German high command might cast about for other ways to take the initiative and vary the daily diet of depressing news from the trenches.
To what extent this is hindsight, is difficult to say; but there were other, more tangible, signs of possible change. The British, by virtue of the Admiralty’s ‘Room 40’, were far ahead of the Germans in signals intelligence. This was substantially, but by no means entirely, a matter of luck. Accounts vary, but there appear to have been two gifts which fell into the Admiralty’s lap early in the war. In August 1914 the Russians salvaged a Signal Book from the wreck of the German cruiser Magdeburg, and passed it on. Then, in November, a sinking German destroyer was alleged to have jettisoned a cipher book (or, alternatively, a grid-map of the North Sea) which was subsequently dragged up in the nets of a Harwich trawler. At any rate, the Admiralty quickly established a network of coastal listening and direction-finding stations, and Room 40 was gleaning so much from German transmissions that the British were obsessively careful over their own use of wireless, with dummy signals to disguise decreases in routine harbour traffic, and a regime of strict silence for ships at sea.
Now, as May progressed, signal decryptions (or ‘Japanese telegrams’, as they were none-too-subtly called) confirmed the withdrawal of U-boats from the Western Approaches: a movement consonant both with the German claim to have ceased attacks on merchant shipping, and with the possibility of imminent fleet operations in the North Sea. And Scheer was indeed planning an exploit – within the ‘Guiding Principle’ that the ‘existing proportion of strength ruled out the High Seas Fleet seeking decisive battle with the Grand Fleet’. A new bombardment of Sunderland by Hipper’s 1st Scouting Group would draw Beatty into a High Seas Fleet trap in the Dogger Bank area, while Zeppelins, acting as airborne cruisers, watched out for Jellicoe to make sure the scheme did not backfire.
Originally scheduled for the 17th of May, owing to repairs to the battlecruiser Seydlitz (damaged by a mine during the Lowestoft and Yarmouth raid), this plan was postponed, first to the 23rd, then to the 29th, while U-boats laid mines off British bases and slid into ambush positions. Finally, it was abandoned, because the weather was deemed unsuitable for Zeppelin reconnaissance; and instead – so as not to waste all the preparations – a less adventurous foray northwards up the Danish coast towards the Skagerrak was arranged for the 31st, the last day before the U-boats’ endurance limits would compel their withdrawal.