▁and , ▁on ▁failing , ▁candidates ▁are ▁prevent ed ▁from ▁serving ▁on ▁sub mar ines ▁in ▁any ▁capacity . ▁ ▁Form ation ▁and ▁history ▁Prior ▁to ▁World ▁War ▁I , ▁knowledge ▁rel ating ▁to ▁command ▁of ▁a ▁sub marine ▁was ▁passed ▁on ▁from ▁a ▁boat ' s ▁commander ▁to ▁his ▁replacement . ▁However ▁high ▁attr ition ▁rates ▁during ▁the ▁war ▁meant ▁this ▁training ▁could ▁not ▁always ▁be ▁passed ▁on , ▁and ▁the ▁less ▁experienced ▁sub marine ▁command ers ▁were ▁in ▁turn ▁more ▁likely ▁to ▁make ▁errors ▁resulting ▁in ▁their ▁death ▁and ▁the ▁loss ▁of ▁the ▁boat . ▁In ▁ 1 9 1 7 , ▁the ▁Royal ▁Navy ▁established ▁the ▁CO Q C ▁for ▁potential ▁command ing ▁officers . ▁ ▁' Per isher ' ▁( as ▁the ▁Sub marine ▁Command ▁Cour se ▁is ▁better ▁known ) ▁is ▁a ▁ 2 4 - week ▁course ▁that ▁officers ▁must ▁take ▁prior ▁to ▁serving ▁as ▁an ▁Executive ▁Officer ▁on ▁board ▁a ▁Royal ▁Navy ▁Sub marine . ▁It ▁has ▁been ▁run ▁twice ▁a ▁year ▁since ▁ 1 9 1 7 , ▁usually ▁starting ▁on ▁ 2 ▁July ▁and ▁ 1 4 ▁November ▁each ▁year . ▁It ▁is ▁widely ▁regarded ▁as ▁one ▁of ▁the ▁t ough est ▁command ▁courses ▁in ▁the ▁world , ▁with ▁a ▁historical ▁failure ▁rate ▁of ▁ 2 5 %. ▁ ▁Following ▁World ▁War ▁II , ▁the ▁Royal ▁Netherlands ▁Navy ▁began ▁to ▁send ▁officers ▁to ▁the ▁course . ▁Until ▁ 1 9 9 5 , ▁the ▁Royal ▁Navy ▁and ▁Royal ▁Netherlands ▁Navy ▁were ▁joint ly ▁responsible