 Markgraf was present for the uneventful advance in the direction of Sunderland on 18 – 20 October . Unit training with the III Squadron followed from 21 October to 2 November . Two days later , the ship formally rejoined III Squadron . On the 5th , a pair of U @-@ boats grounded on the Danish coast . Light forces were sent to recover the vessels , and III Squadron , which was in the North Sea en route to Wilhelmshaven , was ordered to cover them . During the operation , the British submarine <unk> torpedoed both Grosser Kurfürst and Kronprinz and caused moderate damage . For most of 1917 , Markgraf was occupied with guard duties in the North Sea , interrupted only by a refit period in January and periodic unit training in the Baltic . 
