<P> On 5 September 1914 , HMS Pathfinder was sunk by SM U-21 , the first ship to have been sunk by a submarine using a self - propelled torpedo . On 22 September , U-9 sank the obsolete British warships HMS Aboukir , HMS Cressy and HMS Hogue ( the `` Live Bait Squadron '' ) in a single hour . </P>
<P> On 5 September 1914 , HMS Pathfinder was sunk by SM U-21 , the first ship to have been sunk by a submarine using a self - propelled torpedo . On 22 September , U-9 sank the obsolete British warships HMS Aboukir , HMS Cressy and HMS Hogue ( the `` Live Bait Squadron '' ) in a single hour . </P>
when were u boats first used in ww1
when were u boats first used in ww1
5 September 1914
5 September 1914