 A part of the 4th Flotilla throughout the war , U @-@ 70 sank 53 merchant ships with a combined gross register tonnage ( GRT ) of 137 @,@ 775 . Included in that total was Southland — at 11 @,@ 899 GRT , one of the largest ships of the war sunk by a U @-@ boat — sunk in June 1917 . In addition she sank one British Flower @-@ class sloop and damaged four merchant ships ( 20 @,@ 369 GRT ) . On 20 November 1918 , nine days after the Armistice , U @-@ 70 was surrendered to the British . She was broken up at Bo 'ness in 1919 – 20 . 
