 In mid @-@ May , Scheer completed plans to draw out part of the British Grand Fleet . The German High Seas Fleet would sortie for a raid on Sunderland , luring the British fleet across " ' nests ' of submarines and mine @-@ fields " . U @-@ 70 was one of four U @-@ boats that put out to sea beginning on 18 May to scout the central North Sea for signs of the British fleet . Completing five days of scouting , U @-@ 70 , along with U @-@ 63 , U @-@ 51 , U @-@ 32 , sister boat U @-@ 66 , U @-@ 24 , and U @-@ 52 , took up position off the Firth of Forth on 23 May . The other two other boats , U @-@ 43 and U @-@ 44 , were stationed off Pentland Firth , in position to attack the British fleet leaving Scapa Flow . All the boats were to remain on station until 1 June and await a coded message which would report the sailing of the British fleet . Unfortunately for the Germans , the British Admiralty had intelligence reports of the departure of the submarines which , coupled with an absence of attacks on shipping , aroused British suspicions . 
