 U @-@ 70 was launched on 20 July 1915 . On 22 September , SM U @-@ 70 was commissioned into the German Imperial Navy under the command of Kapitänleutnant Otto Wünsche . U @-@ 70 was the second U @-@ boat command for the 30 @-@ year @-@ old officer ; he had commanded U @-@ 25 from August 1914 until a week before assignment to U @-@ 70 . In January 1916 , Wünsche and U @-@ 70 escorted the German blockade runner Marie through the North Sea . On 9 February , U @-@ 70 was assigned to the 4th Flotilla ( German : IV . Uhalbflotille ) in which she remained for the duration of the war . U @-@ 70 served as an escort again in late February , when she accompanied the German merchant raider Greif . 
