▁ 1 9 4 2 ▁but ▁resulted ▁in ▁a ▁failed ▁outcome . ▁ ▁Background ▁ ▁The ▁past ▁Soviet ▁sub marine ▁off ensive ▁in ▁ 1 9 4 2 ▁resulted ▁in ▁heavy ▁losses ▁for ▁the ▁sovi ets ▁but ▁achieved ▁to ▁sink ▁some ▁ships ▁and ▁caused ▁del ays ▁and ▁concern ▁for ▁the ▁Germ ans . ▁This ▁was ▁achieved ▁despite ▁the ▁presence ▁of ▁over ▁ 1 3 0 0 0 ▁def ensive ▁mines . ▁Pre par ations ▁were ▁made ▁in ▁winter ▁ 1 9 4 2 ▁to ▁prevent ▁the ▁intr usion ▁of ▁Soviet ▁sub mar ines ▁in ▁the ▁open ▁Balt ic ▁for ▁the ▁following ▁year . ▁A ▁decis ive ▁element ▁of ▁the ▁A xis ▁block ade ▁was ▁lay ing ▁a ▁double ▁anti - sub marine ▁net , ▁named ▁" W al rus " ▁system , ▁across ▁the ▁G ulf ▁of ▁Finland ▁from ▁P ork k ala ▁( Fin land ) ▁to ▁Na iss aar ▁( Est onia ). ▁Additionally , ▁the ▁German ▁Navy ▁laid ▁▁ 7 , 2 9 3 ▁other ▁new ▁mines , ▁while ▁Finland ▁laid ▁ 1 , 9 6 5 ▁mines , ▁in ▁addition ▁to ▁the ▁existing ▁ones . ▁ ▁Off ensive ▁ ▁At ▁the ▁beginning ▁of ▁the ▁year ▁the ▁S ovi ets ▁could ▁eng age ▁in ▁off ensive ▁four ▁St alin ets - class ▁sub mar ines , ▁nine ▁Sh ch uka ▁class ▁and ▁three ▁Mal y ut ka ▁class . ▁Sh Ch - 3 2 3 ▁was ▁the ▁first ▁vessel ▁to ▁attempt ▁passing ▁the ▁block ade ▁but ▁was ▁s unk ▁by