enough intelligence to intercept one of the big German minesweeping operations, provided that the ships based at Rosyth, in Scotland, could sail in time. The Admiralty decided that an offensive operation should begin on 17 November. Test trip, 17 November The Germans planned a Test trip for 17 November 1917, comprising the 2nd and 6th Auxiliary Mine Sweeper Half-Flotillas, the 12th and 14th Torpedo Boat Half-Flotillas, Barrier Breaking Division IV and light cruisers of Scouting Group Division II, commanded by Rear-Admiral () Ludwig von Reuter from the 6th Mine Sweeper Half-Flotilla. The Kaiser-class battleships, and from Squadron IV, each with ten guns, led by Captain () Kurt Graßhoff in Kaiserin, were to act as covering force for the group. The battleships were to reach a point west of Heligoland by while the Test trip group rendezvoused in the Heligoland Bight about half-way between Horns Reef and Terschelling. With poor weather grounding Zeppelins and making it impossible for light cruisers embark seaplanes, after they had alighted on the sea, the Test trip relied on reconnaissance patrols by two land-based seaplanes from Borkum on the German coast, just east of the Netherlands, for reconnoitring ahead of the group. British plan The German Test trip had been revealed by the code breakers of Room 40, allowing the British to plan an ambush. On 16 November, orders for an attack on the Test trip were sent to Admiral Sir David Beatty, Commander-in-Chief of the British Grand Fleet. On 17 November 1917 a force of cruisers under Vice Admiral Trevylyan Napier was sent to attack the German minesweepers as they were mineweeping. Battle The action began at roughly west of Sylt, when sighted German ships. She opened fire at Reuter with four light cruisers and eight destroyers, advanced towards the British ship to cover the withdrawal of the minesweepers which escaped, except for the trawler , which was sunk. A stern chase ensued as the German forces, making skilful use of smoke-screens, withdrew south-east at their best speed, under fire from the 1st Cruiser Squadron, the 1st Light Cruiser Squadron and the 6th Light Cruiser Squadron. was detached from the 1st Battle Cruiser Squadron and came up at high speed to join the battle. Both sides were hampered in their manoeuvres by the presence of naval minefields. At about the same time, the light cruisers came under fire from Kaiser and Kaiserin, Kaiser-class battleships, which